hypothesis in water cycle

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water cycle

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• NASA - Global Precipitation Measurement - The Water Cycle
• U.S. Geological Survey - The Water Cycle
• Chemistry Libretexts - Water Cycle
• Northwest River Forecast Center - The Water Cycle
• NeoK12 - Educational Videos and Games for School Kids - Water Cycle
• Pennsylvania State University - Department of Energy and Mineral Engineering - Understanding water cycle
• UCAR Center for Science Education - The Water Cycle
• water cycle - Children's Encyclopedia (Ages 8-11)
• water cycle - Student Encyclopedia (Ages 11 and up)

• How does deforestation affect the water cycle?
• What is the significance of the water cycle in maintaining ecosystems?
• What are the main processes of the water cycle and how do they work?
• In what ways can human activities impact the water cycle and subsequently the climate?
• How do clouds contribute to the Earth's climate system?
• What role do plants play in the water cycle?

water cycle , cycle that involves the continuous circulation of water in the Earth - atmosphere system. Of the many processes involved in the water cycle, the most important are evaporation , transpiration , condensation , precipitation , and runoff . Although the total amount of water within the cycle remains essentially constant, its distribution among the various processes is continually changing.

A brief treatment of the water cycle follows. For full treatment, see hydrosphere: The water cycle .

Evaporation , one of the major processes in the cycle, is the transfer of water from the surface of the Earth to the atmosphere. By evaporation, water in the liquid state is transferred to the gaseous , or vapor, state. This transfer occurs when some molecules in a water mass have attained sufficient kinetic energy to eject themselves from the water surface. The main factors affecting evaporation are temperature , humidity , wind speed, and solar radiation . The direct measurement of evaporation, though desirable, is difficult and possible only at point locations. The principal source of water vapor is the oceans , but evaporation also occurs in soils , snow , and ice . Evaporation from snow and ice, the direct conversion from solid to vapor, is known as sublimation. Transpiration is the evaporation of water through minute pores, or stomata, in the leaves of plants . For practical purposes, transpiration and the evaporation from all water, soils, snow, ice, vegetation, and other surfaces are lumped together and called evapotranspiration , or total evaporation.

Water vapor is the primary form of atmospheric moisture. Although its storage in the atmosphere is comparatively small, water vapor is extremely important in forming the moisture supply for dew , frost , fog , clouds , and precipitation. Practically all water vapour in the atmosphere is confined to the troposphere (the region below 6 to 8 miles [10 to 13 km] altitude).

The transition process from the vapor state to the liquid state is called condensation . Condensation may take place as soon as the air contains more water vapour than it can receive from a free water surface through evaporation at the prevailing temperature. This condition occurs as the consequence of either cooling or the mixing of air masses of different temperatures. By condensation, water vapor in the atmosphere is released to form precipitation .

Precipitation that falls to the Earth is distributed in four main ways: some is returned to the atmosphere by evaporation, some may be intercepted by vegetation and then evaporated from the surface of leaves , some percolates into the soil by infiltration, and the remainder flows directly as surface runoff into the sea. Some of the infiltrated precipitation may later percolate into streams as groundwater runoff. Direct measurement of runoff is made by stream gauges and plotted against time on hydrographs.

Most groundwater is derived from precipitation that has percolated through the soil. Groundwater flow rates, compared with those of surface water, are very slow and variable, ranging from a few millimeters to a few meters a day. Groundwater movement is studied by tracer techniques and remote sensing.

Ice also plays a role in the water cycle. Ice and snow on the Earth’s surface occur in various forms such as frost, sea ice , and glacier ice. When soil moisture freezes, ice also occurs beneath the Earth’s surface, forming permafrost in tundra climates . About 18,000 years ago glaciers and ice caps covered approximately one-third of the Earth’s land surface. Today about 12 percent of the land surface remains covered by ice masses.

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Water Cycle

Introduction: (initial observation).

Rain and snow are the main sources of fresh water for people living on the earth. Both rain and snow come from the clouds; but, where do the clouds come from? It often seems that clouds appear from nowhere. One minute the sky is clear and then a few minutes later clouds form. Sometimes clouds come from far places. Wind moves the clouds from one area to the other.

If you live near a lake, ocean or forest, you may have seen water vapors rising from wet surfaces and disappearing in the air. Is it possible that the same vapors become visible again when they get to higher elevations? If the clouds come from oceans, forests and other surface waters then why doesn’t the rain water contain salt and other pollutants that exist in rivers and surface waters?

Is it possible that only pure water evaporates and all impurities stay behind?

In this project you will study, observe and demonstrate the water cycle.

This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Adult supervision and support is required for the experiments of this project.

Information Gathering:

Find out what happens to the water that evaporates. Read books, magazines or ask professionals who might know in order to learn about water evaporation, clouds and precipitation. Keep track of where you got your information from.

Following are samples of information that you may find:

The Water Cycle

Background Information:

Earth was formed 4.6 billion years ago, but water was not present from the very beginning. At some point, possibly because of the heating of hydrogen and oxygen as Earth developed, water vapor began to form in the atmosphere. About 3.8 billion years ago, oceans formed and the cycle began. The same water that you drink today has been around since the oceans formed. Water is an important part of life on this planet. The water cycle is a complex process that gives us water to drink and provides us with climates that allow us to have food to eat. The earth has a limited amount of water, which keeps going around and around. It is a very important cycle in that it allows for life and helps sustain life on earth. Seventy percent of the earth’s surface is covered by water. Yet only 1% of that water is in the form to be used by humans and land animals. Water constantly changes from solid to liquid to gas. This cycle is what we call the water cycle.

Evaporation, condensation, and precipitation are the cycles of the water cycle.

Evaporation occurs when the sun heats up water in our oceans, lakes, and rivers and turns it into vapor or stream. This water vapor leaves the oceans, lakes, and rivers and moves up into the air. The water vapor settles in the troposphere where it condenses.

Condensation happens when warm and cold air meets in the troposphere. The water vapors in the air get cold and excess water condenses into either liquid water or ice, which then form clouds. If enough of this water forms into clouds, rain will begin if the weather is warm. If it is cold, it will snow. This process is called precipitation.

Precipitation is when so much water has condensed that the air cannot hold it any longer. The clouds get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.

Essentially water in liquid form turns into a gas, then into a solid, and finally back into a liquid in a never-ending process.

Suggested References:

Do some research on water cycles, and draw a diagram to help you further understand this important cycle of the earth. Once you understand the water cycle and have done some research on it, you can observe the cycle in your own home. The links below should be very helpful in this preparation process. They should be used as a complement to your own research.

If you live in the United States, there are 40 trillion gallons of water above your head on an average day. Each day, about four trillion gallons of this water fall to Earth as precipitation, such as rain, snow, or hail. Some of the water that falls to Earth soaks into the ground and provides runoff to rivers, lakes, and oceans. The remainder—more than 2.5 trillion gallons—returns to the atmosphere through evaporation, and the process begins again.

This continuous process of precipitation and evaporation is called the water cycle, or hydrologic cycle.

Source…

Evaporation:

Evaporation is when the sun heats up water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air.

Sample Experiment to show condensation

In this experiment we will go through all the water cycles and recreate them at home to further understand how they affect the whole world.

You can observe condensation very simply with a few items from around your house. Pour cold water into a glass and put it out on a hot day. You will see water form on the outside of the glass after a few minutes. Water vapor in the warm air turns back into liquid when it touches the cold glass.

You can also view evaporation very easily in your home. Have a parent assist you with putting some water in a kettle, and letting it come to a boil. As the water in the kettle becomes heated, you can watch the steam rise out of the kettle. The water is evaporating into the air.

You can then take a ceramic plate and put it in your freezer for an hour. Then take the plate out of the freezer and hold it about 1 ft. over the steam rising out of the kettle. Be careful that the steam does not burn your hands. You will see water droplets form on the plate. This is then called condensation. If a lot of water condenses on plate, it will start dripping down and this in turn is called precipitation!

Conclusions:

In this same way that you viewed the water cycle in your home, the water cycle occurs on our earth. What is the importance of what you have just done? Summarize what you just observed in your experiments. Describe exactly what happened and try to think of the implications of these procedures.

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to display water cycle. Show how the light and heat energy from the sun evaporate water and distributes water around the earth.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

As a display project, you will not need to identify variables. In higher grades you may want to study the effect of one specific factor on the rate of evaporation or condensation. That is when you need to define variables.

For example you may want to study the effect of temperature on evaporation of water. In this case temperature will be the manipulated variable. The rate of evaporation is the responding variable.

Another example is when you want to determine the evaporation rate in different days. (Experiment 3) . In this case the independent variable is the day. The dependent variable is the amount of water evaporation from one square foot surface water.

Hypothesis:

Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

In a display project, you will not need to identify variables.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1: What evaporates?

Introduction : Rain and snow do not contain salt and other pollutants usually found in the sea or other surface waters. In this experiment you will test to see if such material may evaporate along with water.

Procedure :

• Make some salty-polluted water by dissolving some salt and some water color in a cup of water.
• Transfer your polluted water to a plate and leave it outside under the sun for water to evaporate.
• After a few days, see weather the salts and water color evaporated or if they remained on the plate.
• Based on the result, write your conclusion.

Experiment 2: Water Displacement?

Introduction : Evaporation, condensation and precipitation are parts of a process that transfer large amounts of water from oceans to dry lands all over the globe on a daily bases.

This process is called water cycle. Without this process rivers, forests and lakes could not exist. In this experiment we will examine the process of water cycle and see how water is transferred from one area to the other.

• Get a two compartment plastic container with a lid that seals perfectly. Make sure that the divider is shorter than the sides of the container; in this way air can freely flow between the two compartments.
• Place the container on a flat surface in a sunny place in your backyard and then place a piece of stone or a block of wood under one side of the container. In this way the container will be slanted to one side.
• Fill the elevated compartment in half with water. Carefully place the lid on and cover the lower compartment with an aluminum foil to keep it cool.
• After 7 days carefully open the container. What do you see in the lower compartment. Can water evaporate from one compartment and condense and precipitate in the other compartment?

Variations:

The above experiment can also be performed in a glass or plastic aquarium.

A slanted glass on top allows the condensations to go towards elevations that you may make using real soil or a block of Styrofoam.

Use plastic plants or dry plants on the elevations to simulate vegetations.

What if we have no sunlight?

A 100 watt flood lamp mounted about 1 foot above the water area can work like sunlight. You may use a timer or manually turn off an on the light every hour to create day and night conditions for your model.

Experiment 3: Rate of water cycle

Introduction : The water cycle starts by evaporation of surface waters and perspiration by plants, and it ends when the water comes back down to the earth in the form of rain or snow. In this experiment you measure and record the amount of water evaporating from surface waters in different days.

Who must do this experiment?

If you are required to have a data table and possibly a graph for your project, you may try this experiment. In most cases 8th grade students are expected to present a data table and a graph with their project report or project display.

Measure 250 milliliters of water in a graduated cylinder and then transfer the water to a flat, square cooking tray. Try to use a tray that has an area of one square foot. If you don’t have a tray that measure one square foot, you can make one using an aluminum foil placed over a cardboard.

Place the tray outside in an open space, away from animals and birds.

After 24 hours transfer the water back to the measuring cylinder and observe the difference. Record how much water was evaporated.

Repeat this experiment in 5 different days and record the amount of evaporated water per square foot. Also record the outdoor weather temperature on those days.

Your results table may look like this:

Calculate and write the average daily evaporation in the last row of your data table.

Make a graph:

You can use a bar graph to visually present your results. Make one vertical bar for each day you repeat your experiment. The height of bar will show the amount of daily evaporation on that day.

If for some reason such as rain or animals your results become invalid, you will have to ignore the results of such days. If you have time, you may repeat your test a few more days to have at least 5 days of reliable results.

Materials and Equipment:

Material used in the above experiments are:

• Water Color
• Clear plastic container with 2 compartment
• Plastic aquarium
• Light bulb (100 watt) to simulate sunlight

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.

Calculations:

No calculations are required for this project.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.

Conclusion:

Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.

References:

List of web references

Water Vapor

Q. Since this project doesn’t have results or data, then how would I set up the project board. Is there an Abstract, conclusion or a purpose?

A. In a display project you do the experiments and write down your observations as the experiment results. Project board will have drawings, pictures and writings similar to what you have in your project guide. In addition to that you also write your observations and what you have learned from your experiments. If you need to have a data table, you can repeat the experiment 2 in 5 different days and record the amount of water displacement every day. Then convert the values to the ratio of total water in the container.

It is always important for students, parents and teachers to know a good source for science related equipment and supplies they need for their science activities. Please note that many online stores for science supplies are managed by MiniScience.

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ENCYCLOPEDIC ENTRY

Water cycle.

The water cycle is the endless process that connects all of the water on Earth.

Conservation, Earth Science, Meteorology

Deer Streams National Park Mist

A misty cloud rises over Deer Streams National Park. The water cycle contains more steps than just rain and evaporation, fog and mist are other ways for water to be returned to the ground.

Photograph by Redline96

Water is one of the key ingredients to life on Earth. About 75 percent of our planet is covered by water or ice. The water cycle is the endless process that connects all of that water. It joins Earth’s oceans, land, and atmosphere.

Earth’s water cycle began about 3.8 billion years ago when rain fell on a cooling Earth, forming the oceans. The rain came from water vapor that escaped the magma in Earth’s molten core into the atmosphere. Energy from the sun helped power the water cycle and Earth’s gravity kept water in the atmosphere from leaving the planet.

The oceans hold about 97 percent of the water on Earth. About 1.7 percent of Earth’s water is stored in polar ice caps and glaciers. Rivers, lakes, and soil hold approximately 1.7 percent. A tiny fraction—just 0.001 percent—exists in Earth’s atmosphere as water vapor.

When molecules of water vapor return to liquid or solid form, they create cloud droplets that can fall back to Earth as rain or snow—a process called condensation . Most precipitation lands in the oceans. Precipitation that falls onto land flows into rivers, streams, and lakes. Some of it seeps into the soil where it is held underground as groundwater.

When warmed by the sun, water on the surface of oceans and freshwater bodies evaporates, forming a vapor. Water vapor rises into the atmosphere, where it condenses, forming clouds. It then falls back to the ground as precipitation. Moisture can also enter the atmosphere directly from ice or snow. In a process called sublimation , solid water, such as ice or snow, can transform directly into water vapor without first becoming a liquid.

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Water Cycle

What is the water cycle.

Water cycle, also known as the hydrologic cycle, involves a series of stages that show the continuous movement and interchange of water between its three phases – solid, liquid, and gas, in the earth’s atmosphere. The sun acts as the primary source of energy that powers   the   water cycle on earth. Bernard Palissy discovered the modern theory of the water cycle in 1580 CE.

Steps of the Water Cycle: How does it Work

1. Change from Liquid to Gaseous Phase – Evaporation and Transpiration

The heat of the sun causes water from the surface of water bodies such as oceans, streams, and lakes to evaporate into water vapor in the atmosphere. Plants also contribute to the water cycle when water gets evaporated from the aerial parts of the plant , such as leaves and stems by the process of transpiration.

2. Change from Solid to Gaseous Phase – Sublimation

Due to dry winds, low humidity, and low air pressure, snow present on the mountains change directly into water vapor, bypassing the liquid phase by a process known as sublimation.

3. Change from Gaseous to Liquid Phase – Condensation

The invisible water vapor formed through evaporation, transpiration, and sublimation rises through the atmosphere, while cool air rushes to take its place. This is the process of condensation that allows water vapor to transform back into liquid, which is then stored in the form of clouds.

Sometimes, a sudden drop in atmospheric temperature helps the water vapors to condense into tiny droplets of water that remain suspended in the air. These suspended water droplets get mixed with bits of dust in the air, resulting in fog.

4. Change from Gaseous to Liquid and Solid Phase – Precipitation and Deposition         

Wind movements cause the water-laden clouds   to collide and fall back on the earth’s surface through precipitation, simply known as rain. The water that evaporated in the first stage thus returns into different water bodies on the earth’s surface, including the ocean, rivers, ponds, and lakes. In regions with extremely cold climate with sub-zero temperatures, the water vapor changes directly into frost and snow bypassing the liquid phase, causing snowfall in high altitudes by a process known as the deposition. 

5. Return of the water back into the underground reserve – Runoff, Infiltration, Percolation, and Collection

The water that falls back on the earth’s surface moves between the layers of soil and rocks and is accumulated as the underground water reserves known as aquifers. This process is further assisted by earthquakes, which help the underground water to reach the mantle of the earth. Some amount of precipitated water flows down the sides of mountains and hills to reach the water bodies, which again evaporates into the atmosphere. During volcanic eruptions, the underground water returns to the surface of the earth, where it mixes with the surface water bodies in order to continue the cycle.

Video: Water Cycle Explained

Why is the water cycle important.

The most crucial and direct impacts of the above process on earth include:

• Making fresh water available to plants and animals, including humans, by purifying the groundwater on earth. During the water cycle, the water evaporates, leaving behind all the sediments and other dust particles. Similarly, for the sustenance of marine life, the saline range of all salt water bodies is kept within a certain permissible limit through infiltration. 
• Allowing even distribution of water on all surfaces of the earth. Water is temporarily stored as clouds in the atmosphere, whereas surface water bodies such as rivers and oceans, together with underground water, form the major permanent water reserves. 
• Causing a cooling effect on earth due to evaporation of water from surface water bodies, which help to form clouds that eventually precipitate down in the form of rain. This way water cycle affects the weather and climate of the earth.
• Ensuring some other biogeochemical cycles , including those concerning oxygen and phosphorus, to continue in nature.
• Cleaning the atmosphere by taking-away dust particles, shoot, and bacteria , thus acting as a means to purify the air we breathe.

Human Impact on Water Cycle

Human activities adversely affect the water cycle in the two following ways:

a) Deforestation : Plants play an important role in the water cycle by preventing soil erosion and thus helps to increase the groundwater level of the earth. Also, plants contribute by absorbing water from the soil, which is then released back to the atmosphere during transpiration. Deforestation adversely affects both the above processes, thus breaking the flow of the water cycle.

b) Pollution : Burning of fossil fuels acts as the major source of air pollution releasing toxic gases into the atmosphere, leading to the formation of smog and acid rain . Water from farmlands run off to the nearest water bodies carrying chemicals such as insecticides and pesticides along with them, thus causing water pollution. The presence of excessive contaminants in the atmosphere and water bodies decreases the evaporation and condensation on earth, thus adversely affecting the water cycle.

Ans. Cellular respiration is the process by which organisms take up oxygen in order to breathe and digest food. Water is utilized for breaking large molecules that release energy in the form of ATP , while in a subsequent step the water molecules are released back into the cell, which in turn returns to the atmosphere, thus affecting the water cycle.

Ans. Rivers contain more water than streams and thus contribute more to the formation of water vapor through evaporation compared to a stream.

• Water Cycle – Britannica.com
• The Water Cycle – Khanacademy.org
• Water Cycle – Noaa.gov
• What Is The Hydrologic Cycle? – Worldatlas.com
• What is the Water Cycle? – Earth.com
• The Water Cycle – Coastgis.marsci.uga.edu

Article was last reviewed on Wednesday, May 17, 2023

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One response to “Water Cycle”

The first part of the water cycle is of course evaporation and transportation, but I don’t want to focus on that, I want to focus on the 2nd step which is sublimation. Sublimation is when snow or hail, or sleet falls down on a mountain and it quickly turns into water vapor by passing the liquid phase.Now lets skip to the last phase which is RIPC

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The water cycle is often taught as a simple circular cycle of evaporation, condensation, and precipitation. Although this can be a useful model, the reality is much more complicated. The paths and influences of water through Earth’s ecosystems are extremely complex and not completely understood. NOAA is striving to expand understanding of the water cycle at global to local scales to improve our ability to forecast weather, climate, water resources, and ecosystem health.

The water cycle. (Image credit: Dennis Cain/NWS)

The water cycle on Earth

Water is essential to life on Earth. In its three phases (solid, liquid, and gas), water ties together the major parts of the Earth’s climate system — air, clouds, the ocean, lakes, vegetation, snowpack offsite link , and glaciers offsite link .

The water cycle shows the continuous movement of water within the Earth and atmosphere. It is a complex system that includes many different processes. Liquid water evaporates into water vapor, condenses to form clouds, and precipitates back to earth in the form of rain and snow. Water in different phases moves through the atmosphere (transportation). Liquid water flows across land (runoff), into the ground (infiltration and percolation), and through the ground (groundwater). Groundwater moves into plants (plant uptake) and evaporates from plants into the atmosphere (transpiration). Solid ice and snow can turn directly into gas (sublimation). The opposite can also take place when water vapor becomes solid (deposition).

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Water, society, and ecology

Water influences the intensity of climate variability and change. It is the key part of extreme events such as drought and floods . Its abundance and timely delivery are critical for meeting the needs of society and ecosystems.

Humans use water for drinking, industrial applications, irrigating agriculture, hydropower, waste disposal, and recreation. It is important that water sources are protected both for human uses and ecosystem health. In many areas, water supplies are being depleted because of population growth, pollution, and development. These stresses have been made worse by climate variations and changes that affect the hydrologic cycle.

A series of atmospheric rivers starting in late December 2022 through mid-January 2023 dropped feet of rain and snow across California and other parts of the West Coast.

Water and climate change

Climate change is affecting where, when, and how much water is available. Extreme weather events such as droughts and heavy precipitation , which are expected to increase as climate changes, can impact water resources. A lack of adequate water supplies, flooding, or degraded water quality impacts civilization — now and throughout history. These challenges can affect the economy, energy production and use, human health, transportation, agriculture, national security, natural ecosystems , and recreation.

An airborne mission finds a global belt of particle formation is making clouds brighter.

EDUCATION CONNECTION

The water cycle impacts ecosystems, economies, and our daily lives. The resources in this collection help teachers guide their students beyond the classic water cycle diagram and through the complex social and environmental issues that surround water. The water cycle provides the opportunity to explore the nature of science using models and empirical evidence. 

Water Cycle

The complete water cycle includes evaporation from oceans and land which is then transported by the atmosphere, together with a small fraction from plant transpiration and from ice sublimation, and precipitates over ocean and land surfaces as rain, snow, freezing rain, sleet, hail, or graupel (graupel is soft hail or snow pellets, precipitation that forms when supercooled water droplets freeze on falling snowflakes). Liquid precipitation over land, joined by melted snow or ice, either penetrates the soil towards aquifers, runs off back to the ocean as rivers, or evapotranspirates back to the atmosphere. A fraction of the water that penetrated the soil also ends up in the ocean as submarine groundwater discharge. Thus the complete water cycle involves the oceans, land, atmosphere, biosphere, and cryosphere. (See below a depiction of Earth’s water cycle; read more about it at NASA’s Earth Observatory website .)

This section focuses on JPL studies of the terrestrial components of the water cycle and highlights how the work of JPL scientists spans various lifecycle stages of satellites missions.

Current Challenges

Water cycle research at the Jet Propulsion Laboratory is geared towards answering the following questions:

• How is Earth’s water cycle changing and what are the implications for hydrologic extremes and water availability?
• To what extent are human activities, especially water management, driving regional and global changes in the water cycle? What are the processes driving water cycle acceleration?
• How does terrestrial water storage modulate heat storage and sea level rise?

We address these challenges by observing and understanding total land water storage, soil moisture, surface water (rivers and lakes), and snow.

Total water storage and GRACE

The Gravity Recovery And Climate Experiment (GRACE) mission measured changes in Earth’s gravity field from 2002 to 2017.  Its successor GRACE Follow-On (GRACE-FO) was launched in 2018 and will provide similar measurements.  Because water is heavy (1000 kg, or one metric ton, per cubic meter!), the movements of water on Earth can be tracked through changes in Earth’s gravity felt from orbit.  Given the extensive 15+ year data record from GRACE, JPL scientists have been able to discover answers to Earth’s water cycle mysteries, including why the increase in sea level appeared to have slowed down: much of the precipitation destined to oceans was temporarily stored on land.  Other JPL studies, also using GRACE, have shown decreased groundwater availability in several regions, and the conditions setting the stage for drought or flood.

Soil moisture and SMAP

The Soil Moisture Active Passive (SMAP) mission was launched in 2015 and successfully measures changes in soil moisture around the world.  Given that the time range of data from SMAP is still relatively short, much effort has gone into interpreting the SMAP data together with measurements on the ground.

Over one-third of the global land area undergoes a seasonal transition between predominantly frozen and non-frozen conditions each year, with the land surface freeze/thaw (FT) state a significant control on hydrological and biospheric processes over northern land areas and at high elevations. Initial data from SMAP’s radar also captured the 2015 spring thaw progression over the Northern Hemisphere, with a thaw front extending from predominantly non-frozen southern latitudes to the still-frozen north (Derksen, Xu, Dunbar, et al., 2017). This kind of work links the water and carbon cycles.

SMAP is also able to measure ocean salinity, which enabled JPL-led studies to focus on both sides of the land/sea continuum.  Fournier, et al. (2016) presented the first such two‐sided analysis, focusing on the May 2015 severe flooding in Texas. Their investigation benefited from simultaneous measurements of land surface soil moisture and sea surface salinity, both from SMAP, as well as ancillary data.

Surface Water and SWOT

The Surface Water and Ocean Topography (SWOT) mission is the first satellite mission specifically designed to observe the rivers and lakes on Earth’s continents.  SWOT is currently expected to launch in late 2021 and JPL scientists are working to help with satellite design decisions in order to guarantee the best return on investment for NASA.    An example of this is an effort to quantify see how fast SWOT data will need to be made available to users so they can track conditions that quickly change, like water moving through Earth’s rivers.

Snow and ASO

Understanding the amount of water stored as snow in mountains is critical for water managers, particularly for the cities that are located downstream of these mountains.  As NASA investigates potential designs for future Earth orbiting satellites to observe snow, JPL scientists are studying potential measurement strategies using airplanes before using spacecrafts.  The Airborne Snow Observatory (ASO, Painter, Bormann et al, 2017) is an example of such a strategy to measure snowpack.

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When and how was the water cycle discovered?

When and how was the water cycle discovered? Did people, like ancient Greek philosophers, have any correct ideas on the water cycle? Was its discovery more of a recent thing?

• discoveries
• earth-sciences

• 2 $\begingroup$ Some argue that the water cycle was completely understood by Hebrew scholars as evidenced by the text fom the Hebrew bible dated as early as the 10th century BCE. $\endgroup$ –  nwr Commented Feb 9, 2020 at 20:22
• 2 $\begingroup$ " The first published thinker to assert that rainfall alone was sufficient for the maintenance of rivers was Bernard Palissy (1580 CE), who is often credited as the "discoverer" of the modern theory of the water cycle. Palissy's theories were not tested scientifically until 1674, in a study commonly attributed to Pierre Perrault. " $\endgroup$ –  Conifold Commented Feb 10, 2020 at 8:18
• $\begingroup$ It was understood in a general way in the ancient world. $\endgroup$ –  Mozibur Ullah Commented Dec 5, 2020 at 17:30
• $\begingroup$ This article discusses this topic of the water cycle. I recommend giving it a read: Science and the Bible $\endgroup$ –  Peter Peterson Commented Apr 14, 2021 at 8:49

In Aristotles Meteorology , we have:

Now, the sun, moving as it does, sets up processes of change and becoming and decay, and by it's agency the finest and the sweetest water is carried up and is dissolved into vapour and rises to the upper region, where it is condensed again by the cold and so returns the earth.

And he notes this again in his Physics that:

Zeus does not send the rain in order to make the corn grow: it comes of neccessity. The stuff which has been drawn up is bound to cool, and having cooled, turns to water and comes down. It is merely concurrent that this having happened, the corn grows.

Hence, the hydrological or water cycle, at least in Europe, was known by Aristotles time, and so by 350 BCE.

Not the answer you're looking for? Browse other questions tagged discoveries earth-sciences or ask your own question .

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Precipitation and the Water Cycle

Precipitation is water released from clouds in the form of rain, freezing rain, sleet, snow, or hail. Precipitation is the main way atmospheric water returns to the surface of the Earth. Most precipitation falls as rain.

•   Water Science School HOME   •  Water Basics topics   •  The Water Cycle   •

Water cycle components   »   Atmosphere   ·   Condensation   ·   Evaporation   ·   Evapotranspiration   ·   Freshwater lakes and rivers    ·   Groundwater flow   ·   Groundwater storage   ·   Ice and snow   ·   Infiltration   ·   Oceans   ·   Precipitation   ·   Snowmelt   ·   Springs   ·   Streamflow   ·   Sublimation   ·   Surface runoff

Clouds  floating overhead contain water vapor and cloud droplets, which are small drops of condensed water. These droplets are way too small to fall as precipitation, but they are large enough to form visible clouds. Water is continually  evaporating and condensing   in the sky. If you look closely at a cloud, you can see some parts disappearing (evaporating) while other parts are growing (condensing). Most of the condensed water in clouds does not fall as precipitation because their fall speed is not large enough to overcome updrafts which support the clouds. 

For precipitation to happen, first tiny water droplets must condense on even tinier dust, salt, or smoke particles, which act as a nucleus, binding them together. Water droplets may grow as a result of additional condensation of water vapor when the particles collide. If enough collisions occur to produce a droplet with a fall velocity which exceeds the cloud updraft speed, then it will fall out of the cloud as precipitation. This is not a trivial task since millions of cloud droplets are required to produce a single raindrop.  

A more efficient mechanism for producing a precipitation-sized drop, is a process which leads to the rapid growth of ice crystals at the expense of the water vapor present in a cloud. These crystals may fall as snow, or melt then fall as rain. This process is known as the Bergeron-Findeisen process.

How much water falls during a storm? 

You might be surprised at the number of gallons of water that fall from the sky in even a small but intense storm. One inch of rain falling on just a single acre results in 27,154 gallons of water on the landscape. If you'd like to know how much water falls during a storm, use our Interactive Rainfall Calculator ( English units  or  Metric units ) . Just enter an area size and rainfall amount and see how many gallons of water reach the ground.   

What do raindrops look like?

Small raindrops, those with a radius of less than 1 millimeter (mm), are spherical, like a round ball. As droplets collide and grow in size, the bottom of the drop begins to be affected by the resistance of the air it is falling through. The bottom of the drop starts to flatten out until at about 2-3 mm in diameter the bottom is quite flat with an indention in the middle - much like a hamburger bun. Raindrops don't stop growing at 3 millimeters, though, and when they reach about 4-5 mm, things really fall apart. At this size, the indentation in the bottom greatly expands forming something like a parachute. The parachute doesn't last long, though, and the large drop breaks up into smaller drops.   

Precipitation rates vary geographically and over time

In 2017, Colombia received the greatest amount of precipitation at 3,240 mm for the year. Contrast that with Egypt for the same year, during which they received only 18 mm of precipitation for the year. Explore more annual precipitation data on this interactive site from Our World in Data or at  Precipitation Climatology | NASA Global Precipitation Measurement Mission .  

Precipitation size and speed

Have you ever watched a raindrop hit the ground during a large rainstorm and wondered how big the drop is and how fast it is falling? Or maybe you've wondered how small fog particles are and how they manage to float in the air. The table below shows the size, velocity of fall, and the density of particles (number of drops per square foot/square meter of air) for various types of precipitation, from fog to a cloudburst. 

Source: Lull, H.W., 1959, Soil Compaction on Forest and Range Lands, U.S. Dept. of Agriculture, Forestry Service, Misc. Publication No.768

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How does the water cycle work?

Water molecules are heated by the sun and turn into water vapor that rises into the air through a process called evaporation. Next, the water vapor cools and forms clouds, through condensation. Over time, the clouds become heavy because those cooled water particles have turned into water droplets. When the clouds become extremely heavy with water droplets, the water falls back to earth through precipitation (rain, snow, sleet, hail, etc). The process continues in a cyclical manner.

Learn more about Earth's water cycle on the Precipitation Education website.

Freshwater seems abundant, but when accounting for all the water on Earth, it's in limited supply. Just three percent of the water on our planet is freshwater. A majority of this water, about two percent of the world total, is contained in glaciers and ice sheets or stored below ground. The remaining one percent is found in lakes, rivers and wetland areas or transported through the atmosphere in the form of water vapor, clouds and precipitation. Rain and snowfall replenish freshwater sources, making it vital to know when, where and how much water is falling at any given time. Using NASA's Global Precipitation Measurement satellite, researchers can track precipitation worldwide and monitor levels from space. For more information, visit http://water.usgs.gov/edu/earthwherew ... This video is public domain and can be downloaded at: http://svs.gsfc.nasa.gov/goto?11619

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• Biology Article

Water Cycle

What is the Water Cycle? Water Cycle Diagram Stages of Water Cycle Implications of Water Cycle Frequently Asked Questions

What is the Water Cycle?

Water Cycle Diagram

During this process, water changes its state from one phase to another, but the total number of water particles remains the same. In other words, if it were possible to collect and boil 100 gms of water, it will still retain a mass of 100 gms as steam. Likewise, if 100 gms of steam is collected and condensed, the resultant water would still weight 100 gms.

Water changes its state through a variety of processes from evaporation, melting and freezing, to sublimation, condensation, and deposition. All these changes require the application of energy.

Stages of Water Cycle

There are many processes involved in the movement of water apart from the major steps given in the above water cycle diagram. Listed below are different stages of the water cycle.

1. Evaporation

The sun is the ultimate source of energy, and it powers most of the evaporation that occurs on earth. Evaporation generally happens when water molecules at the surface of water bodies become excited and rise into the air. These molecules with the highest kinetic energy accumulate into water vapour clouds. Evaporation usually takes place below the boiling point of water. Another process called evapotranspiration occurs when evaporation occurs through the leaves of plants. This process contributes to a large percentage of water in the atmosphere.

2. Sublimation

Sublimation occurs when snow or ice changes directly into water vapour without becoming water. It usually occurs as a result of dry winds and low humidity. Sublimation can be observed on mountain peaks, where the air pressure is quite low. The low air pressure helps to sublimate the snow into water vapour as less energy is utilised in the process. Another example of sublimation is the phase where fog bellows from dry ice. On earth, the primary source of sublimation is from the ice sheets covering the poles of the earth.

3. Condensation

The water vapour that accumulated in the atmosphere eventually cools down due to the low temperatures found at high altitudes. These vapours become tiny droplets of water and ice, eventually coming together to form clouds.

4. Precipitation

Above 0 degrees centigrade, the vapours will condense into water droplets. However, it cannot condense without dust or other impurities. Hence, water vapours attach itself on to the particle’s surface. When enough droplets merge, it falls out of the clouds and on to the ground below. This process is called precipitation (or rainfall). In particularly cold weather or extremely low air pressure, the water droplets freeze and fall as snow or hail.

5. Infiltration

Rainwater gets absorbed into the ground through the process of infiltration. The level of absorption varies based on the material the water has seeped into. For instance, rocks will retain comparatively less water than soil. Groundwater can either follows streams or rivers. But sometimes, it might just sink deeper, forming aquifers.

If the water from rainfall does not form aquifers, it follows gravity, often flowing down the sides of mountains and hills; eventually forming rivers. This process is called runoff. In colder regions, icecaps form when the amount of snowfall is faster than the rate of evaporation or sublimation. The biggest icecaps on earth are found at the poles.

All the steps mentioned above occur cyclically with neither a fixed beginning nor an end.

Also Read:  Back to the Oceans

Implications of Water Cycle

• The water cycle has a tremendous impact on the climate. For instance, the greenhouse effect will cause a rise in temperature. Without the evaporative cooling effect of the water cycle, the temperature on earth would rise drastically.
• The water cycle is also an integral part of other biogeochemical cycles.
• Water cycle affects all life processes on earth.
• The water cycle is also known the clean the air. For instance, during the process of precipitation, water vapours have to attach themselves on to particles of dust. In polluted cities, the raindrops, apart from picking up dust, also pick up water-soluble gas and pollutants as they fall from the clouds. Raindrops are also known to pick up biological agents such as bacteria and industrial soot particles and smoke.

Read more about the water cycle with diagram by registering @  BYJU’S Biology

• Biogeochemical cycles
• Oxygen Cycle
• Carbon Cycle
• Nitrogen Cycle

Frequently Asked Questions

What are the major 4 steps in the water cycle.

The major 4 steps are evaporation of water, then condensation, precipitation and collection. The sun evaporates water sources and contributes to the formation of water vapor. These water vapour accumulate in the atmosphere as clouds. The vapours condense into water droplets and when enough droplets merge, it falls out of the clouds as rain.

What is the difference between evaporation and condensation?

Evaporation is a process by which water changes into water vapour. Condensation is an opposite process by which water vapour is converted into tiny droplets of water.

Why is water cycle important?

Water cycle has a huge impact on determining the global climate. It is also an integral part of other biogeochemical cycles. It affects all life processes on Earth either directly or indirectly.

Put your understanding of this concept to test by answering a few MCQs. Click ‘Start Quiz’ to begin!

Select the correct answer and click on the “Finish” button Check your score and answers at the end of the quiz

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The Water Cycle

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NOAA Water Cycle Resources

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You may think every drop of rain falling from the sky, or each glass of water you drink, is brand new, but it has always been here, and is a part of the water cycle.  At its most basic, the water cycle is how water continuously moves from the ground to the atmosphere and back again.  As it moves through this cycle, it changes forms.  Water is the only substance that naturally exists in three states on Earth – solid, liquid, and gas.

Over 96% of total global water is in the ocean, so let’s start there.  Energy from the sun causes water on the surface to evaporate into water vapor – a gas.  This invisible vapor rises into the atmosphere, where the air is colder, and condenses into clouds.  Air currents move these clouds all around the earth.

Water drops form in clouds, and the drops then return to the ocean or land as precipitation - let’s say this time, it’s snow.  The snow will fall to the ground, and eventually melts back into a liquid and runs off into a lake or river, which flows back into the ocean, where it starts the process again.

That’s just one path water can take through the water cycle.  Instead of snow melting and running off into a river, it can become part of a glacier and stay there for a long, long time.  Or rain can seep into the ground and become groundwater, where it’s taken up by plants.  It can then transpirate to gas directly through the leaves and return to the atmosphere.  Or, instead of being taken up by the plant, the groundwater can work its way up to a lake, river, spring, or even the ocean.

As you can see, the water cycle can be a very complicated process.  And all its paths through Earth’s ecosystems are complex and not completely understood.

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The water cycle.

Below, you'll find some helpful information and links to experiments and resources about the water cycle for use in the classroom or at home. We hope these resources help you introduce the importance of clean, safe water to your students.

The Water Project is dedicated to providing clean, safe water to people in the developing world who suffer needlessly without it. We hope you'll introduce our work to your students or classmates.

The Water Cycle - What is It?

Read more here »

Interactive Water Cycle Presentation A flash animated activity that lets you control the water cycle as you learn. (FLASH Required)

The USGS Water Cycle Presentation (No Flash Needed)

Water Cycle Downloadable Poster

Create a Mini Water Cycle Create a mini water cycle using a bowl, a mug, some plastic wrap and a rubber band to show how evaporation, condensation and precipitation occur in a closed system.

The Water Cycle & The Water Crisis (PDF) Learn what happens when the water cycle doesn't work for people. Discover how simple interventions can restore balance in the system and how you can help.

Evaporation

All Dried Up A simple experiment showing how evaporation rates are different based on the amount of light a cup of water receives.

The Case of the Disappearing Water (PDF) This lesson includes a story about a missing person where one of the few clues is a cup of water that has partially evaporated. Students must conduct an experiment to see how long it takes for the given amount of water to evaporate in order to find out where the missing person is located. While meant for grades 4-6, the story could easily be rewritten for older grades as a "forensic science" case.

Water Purification by Evaporation and Condensation (PDF) An activity to illustrate how the water cycle helps to purify water.

Condensation

Make a Cloud in a Bottle Highlighting the concepts of air pressure and temperature in cloud making, this experiment uses a burnt match and some water to create a cloud inside of a plastic bottle. Due to the use of matches an adult is necessary.

Precipitation

The Rainmaker This experiment uses a burner to heat water and a cookie tray of ice cubes above it to show how water vapor turns into precipitation like rain.

Collection (and Conservation)

Leaky Faucets Matter This activity challenges students to be more aware of leaks in their house by showing just how much water can be lost through a single leaky faucet over time.

** PLEASE NOTE: All of the links in the "Resources" section of our website are provided for your convenience. The Water Project, Inc. does not endorse any of the linked content. The owners and creators of the content on these third-party sites are solely responsible for that content. If you have concerns about any of these links, please note its URL and contact us here .

The Water Cycle

Why the water cycle does not produce clean water.

The water cycle describes the movement of all water on earth and is a major contributor to the earth's ability to facilitate life. While the water cycle is continuous, much of the activity starts in the oceans, where the majority of earth's water is stored. Oceans and other standing bodies of water are heated by the sun, raising their temperature and causing evaporation. The evaporated water vapor rises to the earths atmosphere and accumulates. After enough saturation, the vapor becomes precipitation and falls back to the earth as rain or snow. This precipitation is distributed throughout the earth, often settling below the ground, running into rivers, or falling into lakes and oceans.

If the water cycle constantly replenishes the earth's water supply, doesn't that mean it should be safe to drink? Unfortunately not. While much of this water looks clean and clear, waterborn organisims may still be in the water, making drinkers vulnerable to deadly disease. All standing water requires adequate treatment and filtration in order to be safe.

Aqua Clara International makes it our mission to increase the availibility of clearn drinking water throughout the world. In many places, communities do not have the resources for adequate filtration. To this end, we have developed cheap and sustainable filters that can be installed and maintained at low cost. In addition, we've developed a universal filter designed to fit most water filtration systems used in American homes. The sales of these domestic filters are used to fund projects abroad. To learn more about our filters or Aqua Clara, visit our website .

About Aqua Clara International

Scientists long ago discovered how to purify unsafe water.  To us, the central issue has been in designing solutions that are both sustainable and scalable and that can reach the millions in need while at the same time continuing to function without sustained outside input.  Our target populations are those individuals and families who live on $2 per day or less.

We are a technology transfer organization. Our niche in clean water continues to be in designing science-based technologies that utilize locally available materials where possible and then transferring what we learn to those working in areas of need.  The cost of our technologies varies by country and is dependent on the prevailing costs of raw materials, such as plastic containers, PVC piping, sand, etc. Learn more by visiting our website .

Aqua Clara International is a 501(c)(3) nonprofit organization (EIN 37-1518655)

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• An Introduction to Water Quality
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What do you want to find out about your study site’s water quality, how will I measure it and what are your predictions?

Check Your Thinking: Scenario: There is an abandoned mine dump within 5 meters of your study site stream. How might contaminants in the mine waste be impacting your stream? When would be the best time of year/day to collect water monitoring data that could help answer this question? What tests should you conduct?

Using your recorded observations and information compiled in the first step, the next step is to come up with a testable question. You can use the previously mentioned question (Based on what I know about the pH, DO, temperature and turbidity of my site, is the water of a good enough quality to support aquatic life?) as it relates to the limitations of the World Water Monitoring Day kit, or come up with one of your own.

What results do you predict? For example, your hypothesis may be “I believe the pH, DO, temperature and turbidity of the water at my study site are of good enough quality to support aquatic life because there are no visible impacts to water quality upstream or on the site.” Once you’ve formulated your question, begin planning the experiment or, in this case, the water monitoring you will conduct .

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The MSP project is funded by an ESEA, Title II Part B Mathematics and Science Partnership Grant through the Montana Office of Public Instruction. MSP was developed by the Clark Fork Watershed Education Program and faculty from Montana Tech of The University of Montana and Montana State University , with support from other Montana University System Faculty.

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Water Cycle Project

Here are three hands on water cycle experiments. These are inspirations and fun experiments for teachers, homeschool parents, and science fair projects.

What Is Water Cycle?

Water cycle is also known as hydrologic cycle or hydrological cycle. It describes how water moves continuously on Earth.

Water loops through different stages – evaporation , condensation , precipitation   and flow. It then goes back to the evaporation stage.

The whole cycle starts all over again and hence the name “water cycle”.

Stages Of The Water Cycle

Water covers 70% of the Earth’s surface and makes up approximately 60% of our bodies. This amazing natural resource is essential for life in both animals and plants.

Besides having many amazing properties , water is the only substance that appears on Earth naturally in all three physical states of matter — gas (water vapor), liquid (water), and solid (snow, ice). Most other substances only exist in one state in nature.

As water goes through the different stages of the water cycle, it changes from one form to anther by absorbing or releasing heat energy in the process.

Water Cycle Experiment 1

Simple Water Cycle In A Bag Experiment

In this simple “water cycle in a bag” experiment, we will observe the different stages of the  water cycle process  up close.

• a ziplock plastic bag (I used 2 Gallon bag)
• color markers (e.g. Sharpie Permanent Markers or any non-erasable markers)
• blue food coloring (optional)
• packing tape
• adult supervision

Instructions

• Warm up the water until steam starts to rise but do not let it boil.
• Add blue food coloring into the water to represent ocean water.
• Pour the water into a ziplock bag and zip it up.
• Hang the bag upright on the window (or the door like I did) using packing tape.
• As the water evaporates, vapors rise and condense at the top of the bag. A white patch can be seen resembling clouds in the upper atmosphere.

• If the water is still warm or if the bag is left on the window facing sunlight, it will keep cycling through the four different stages of the water cycle.

Explore more about the water cycle by answering these questions.

• Can you describe the relationship between the water cycle and living things?
• How does snow fit into the water cycle process?
• What causes soil erosion?
• Have you seen the four stages of the water cycle appear in our daily lives?

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Evaporation

Evaporation takes place wherever there is exposed water, e.g. on the surface of the ocean, rivers or lakes, when we sweat, when animals sweat and when plants transpire .

When the sun heats up exposed water, the water on the surface turns into vapor and goes into the air.

Evaporation can happen at any temperature, but warm water evaporates faster than cold water. If you boil the water, you can see steam rising from the surface. That is a fast, visible evaporation.

Water Cycle Experiment 2

Evaporation-Distillation Water Science

In this water cycle project, let's make our own distilled water using evaporation, one of the important properties of water.

• plastic food wrap
• a small, slightly weighty object (you can use things like a stuffed toy)
• food coloring (optional)
• a large bowl
• a small cup (make sure it's shorter than the large bowl)
• Pour warm water into the large bowl.
• Add food coloring if you want to see  how the distilled water turns out different.

• Wrap the mouth of the bowl with cling wrap.

• Set the bowl under the sun and wait.

Condensation

Condensation leads to cloud formation.

When invisible water vapors in the air rise and reach the upper atmosphere, the cold temperature causes them to release heat and change back into liquid form. These fine water droplets hang on dust particles in the air in the form of clouds.

Precipitation

As water droplets collide and condense together in the upper atmosphere, they grow larger and heavier.

When the water droplets’ fall speed exceeds the cloud updraft speed, they fall out of the cloud as precipitation in the form of rain, freezing rain, sleet, snow or hail.

Water Cycle Experiment 3

Make Your Own Rain - Water Cycle In A Bottle Science Experiment

Let's make rain!

• a clear bottle
• Fill the bottle with water to about 1 inch high.
• Place the bottle by a window that can receive direct sunlight.
• Wait (while you do something else).

Through precipitation, water falls back onto the Earth’s surface.

The flow of water ends up in the rivers, lakes or seas as ocean water . Some soaks into the ground and becomes ground water, which feeds the plants or runs through the soil ending up in the ocean. Some is consumed by animals.

From there, the water cycle starts all over again.

Water Experiment Kits

Water properties have many significant impacts on the environment we live in. Learn more about the different properties of water in these science experiments using water . 

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JSmol Viewer

Spatial and seasonal variations in iron and the response of chlorophyll-a in zhanjiang bay, china.

Graphical Abstract

1. Introduction

2. materials and methods, 2.1. overview of the study area and monitoring station arrangement, 2.2. sample collection and analysis, 2.3. quality control, 2.4. research methods, 2.4.1. calculation method for land-based iron input flux, 2.4.2. correlation analysis, 2.4.3. data statistics and analysis methods, 3. results and analysis, 3.1. spatiotemporal variations in iron content in the coastal seawater of zhanjiang bay, 3.2. spatiotemporal variations in terrestrial input iron in zhanjiang bay, 3.3. variations in environmental factors in the coastal seawater of zhanjiang bay, 3.4. the relationship between iron and nutrients, chlorophyll-a, and other environmental factors in zhanjiang bay, 4. discussion, 4.1. comparison of fe concentration in zhanjiang bay with other estuaries and bays around the world, 4.2. correlation analysis of iron in zhanjiang bay waters with other environmental factors, 4.3. impact of terrestrial iron inputs on the coastal seawater of zhanjiang bay, 4.4. impact of iron on primary productivity in the bay waters, 5. conclusions, author contributions, data availability statement, acknowledgments, conflicts of interest.

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Chen, Z.-L.; Shi, L.-L.; Peng, D.-M.; Chen, C.-L.; Zhang, J.-B.; Zhang, P. Spatial and Seasonal Variations in Iron and the Response of Chlorophyll-a in Zhanjiang Bay, China. Water 2024 , 16 , 2338. https://doi.org/10.3390/w16162338

Chen Z-L, Shi L-L, Peng D-M, Chen C-L, Zhang J-B, Zhang P. Spatial and Seasonal Variations in Iron and the Response of Chlorophyll-a in Zhanjiang Bay, China. Water . 2024; 16(16):2338. https://doi.org/10.3390/w16162338

Chen, Zi-Liang, Li-Lan Shi, De-Meng Peng, Chun-Liang Chen, Ji-Biao Zhang, and Peng Zhang. 2024. "Spatial and Seasonal Variations in Iron and the Response of Chlorophyll-a in Zhanjiang Bay, China" Water 16, no. 16: 2338. https://doi.org/10.3390/w16162338

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• Published: 21 August 2024

Diurnal humidity cycle driven selective ion transport across clustered polycation membrane

• Yuanyuan Zhao   ORCID: orcid.org/0000-0001-6119-3385 1 , 2 ,
• Gang Lu   ORCID: orcid.org/0000-0002-4247-2319 4 ,
• Jinliang Zhang 3 ,
• Liyang Wan 5 ,
• Shan Peng 6 , 7 ,
• Chao Li   ORCID: orcid.org/0000-0002-6208-8269 8 ,
• Yanlei Wang   ORCID: orcid.org/0000-0002-2214-8781 1 , 3 ,
• Mingzhan Wang   ORCID: orcid.org/0000-0003-1956-9769 9 ,
• Hongyan He   ORCID: orcid.org/0000-0003-1291-2771 3 ,
• John H. Xin   ORCID: orcid.org/0000-0001-9965-7421 2 ,
• Yulong Ding   ORCID: orcid.org/0000-0001-8490-5349 10 &
• Shuang Zheng   ORCID: orcid.org/0000-0002-7175-8316 6  

Nature Communications volume  15 , Article number:  7161 ( 2024 ) Cite this article

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• Molecular self-assembly

The ability to manipulate the flux of ions across membranes is a key aspect of diverse sectors including water desalination, blood ion monitoring, purification, electrochemical energy conversion and storage. Here we illustrate the potential of using daily changes in environmental humidity as a continuous driving force for generating selective ion flux. Specifically, self-assembled membranes featuring channels composed of polycation clusters are sandwiched between two layers of ionic liquids. One ionic liquid layer is kept isolated from the ambient air, whereas the other is exposed directly to the environment. When in contact with ambient air, the device showcases its capacity to spontaneously produce ion current, with promising power density. This result stems from the moisture content difference of ionic liquid layers across the membrane caused by the ongoing process of moisture absorption/desorption, which instigates selective transmembrane ion flux. Cation flux across the polycation clusters is greatly inhibited because of intensified charge repulsion. However, anions transport across polycation clusters is amplified. Our research underscores the potential of daily cycling humidity as a reliable energy source to trigger ion current and convert it into electrical current.

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Introduction.

Strategic utilization of environmental resources is crucial for human survival, offering a plethora of essential energy resources 1 , 2 , 3 , 4 . For instance, sunlight, an electromagnetic radiation, furnishes heat and, more importantly, serves as a source of solar energy 5 , 6 , 7 . Solar panels, laden with semiconductors like silicon, transform sunlight into electrical current, presenting a renewable, sustainable energy source for our daily consumption 5 , 7 . Moreover, diurnal humidity cycle, denoting the day-to-day changes in environmental moisture levels, have far-reaching effects from influencing human health and the life cycles of plants and animals to shaping broader environmental and industrial patterns 8 , 9 , 10 . Despite the extensive monitoring of air humidity for weather predictions, minimal efforts have been employed to harness the potential of ambient humidity cycles as a resource to benefit humanity 11 , 12 , 13 , 14 , 15 . Future endeavors in this direction could unlock more sustainable and eco-friendly solutions, thereby improving human life.

Transmembrane ion flux, the directed movement of ions across biological membranes 1 , 16 , 17 , can be precisely tailored and utilized, yielding significant benefits in diverse areas like physiological research 18 , 19 , medical interventions, and drug discovery 9 , 20 , 21 . A prime example of this manipulation’s practicality lies in osmotic energy conversion, where the migration of water from areas of low solute concentration (freshwater) towards those of higher concentration (saltwater) creates a pressure variance 22 , 23 , 24 , 25 . This differential pressure can be exploited to drive a turbine or generate electricity 26 , 27 , 28 , 29 . Therefore, the strategic control of transmembrane ion flux offers promising opportunities for human life enhancement and progressive technological evolution 29 , 30 . In our study, we highlight the substantial potential in using ambient humidity cycle as a spontaneous and continuous driver for selective transmembrane ion transport. We further apply this technology by integrating it into meticulously engineered microfluidic devices, which underscores the significant potential of this strategy for energy harvesting.

Ambient humidity cycle-induced transmembrane ion flux

Ionic liquids (ILs), often labeled as ‘non-volatile’ solvents due to their resistance to evaporation, are highly valuable in various industries, including flexible electronics and energy conversion 31 , 32 , 33 . ILs demonstrate a spectrum of hygroscopic properties, ranging from highly hygroscopic types like imidazolium halide to less hygroscopic varieties such as imidazolium bistriflimide. For our device, we specifically chose protic ILs with chloride anions for two main reasons. Firstly, the effectiveness of our device depends on the interaction between air moisture and the IL, making the highly hygroscopic protic ILs an ideal choice. Secondly, we selected chloride as the ion to facilitate the conversion of ion current into detectable electrical output because of its effective interaction with the electrodes. The dynamics of protic ILs with moisture, involving both absorption and desorption processes, are crucially influenced by the surrounding humidity levels. During high humidity conditions, the IL tends to absorb water molecules from the air more vigorously. Conversely, in low humidity settings, the IL more readily releases water molecules back into the environment.

Our strategy is based on the daily humidity cycle, which refers to the consistent changes in humidity levels experienced over a 24-h period. This change is a continuous cycle that happens every day. When ILs are exposed to varying atmospheric humidity, they will experience a constant disequilibrium with the ambient moisture levels, indicating a perpetual shift in water content. Our device comprises a polycationic membrane sandwiched between two layers of ILs, each with a thickness of 2 mm (Fig.  1a ). One of these IL layers is air-isolated (isolated layer) while the other is exposed to the atmospheric conditions (open layer). With increasing or decreasing humidity, the water content in the open layer varies, deviating from the state of the isolated layer. As the isolated layer’s water content lags behind that of the open layer. This persistent discrepancy in water content across the membrane prompts ion flux, which is selectively regulated by the polycationic membrane.

a Schematic representation of transmembrane concentration imbalance caused by humidity cycle triggered moisture absorption/desorption of IL. This setup comprises two IL layers enveloping a polycationic membrane, with one layer insulated from the air, while the other is left exposed for direct atmospheric interaction. As the ambient humidity is regularly fluctuating, there will be a continuous concentration imbalance. Inset represents schematic of concentration imbalance induced selective transmembrane ion flux. b Three-day continuous monitoring of ion current ( I sc ) from the aforementioned system during outdoor tests, coupled with the tracking of the corresponding ambient humidity ( φ RH ). c , d Tracking of I sc during periods of increasing and decreasing ambient humidity, illustrating a strong correlation between humidity cycles and ion current.

In our preliminary investigations, we positioned our devices in an open-air environment while keeping them shielded from direct sunlight. We meticulously tracked and depicted the variations in humidity using data collected by hygrometer. In order to validate our hypothesis that continuous changing in humidity could consistently stimulate a transmembrane ion current, we observed the short-circuit current ( I sc ) across our device over a period of 3 days. As presented in Fig.  1b , the setup could maintain an uninterrupted ion current with I sc fluctuating from ~−14.6 to 17.9 μA. These variations corresponded to changes in relative humidity (RH) between 51.3% and 95.5%. The ongoing current output can be credited to the constant shifts in water content saturation spurred by fluctuating humidity levels, which assures that the exposed IL layer remains either unsaturated or oversaturated. We further advanced our testing by subjecting our devices to practical air conditions with either increasing or decreasing humidity levels (Fig.  1c, d ). The outcomes demonstrated a reversal in ion current direction corresponding to the change in humidity trend. Above evidence collectively suggests that the ambient humidity cycle facilitates the achievement of selective transmembrane ion flux.

The diurnal humidity cycle is a universal process that occurs in the same consistent fashion throughout the world. The studies above use this daily fluctuation of environmental humidity to create a continuous and sustainable driving force for ion flux and energy conversion. While photovoltaic cells and wind turbines are limited by specific weather conditions and geography, this approach of ours does not and, therefore, can give an even flow of energy every time, independent of the day and the weather. This makes it particularly suitable for areas with consistent low-power requirements. This is well exemplified by solar panels, which perform best in high-irradiance environments and variable-free stable weather conditions (mainly constant clear weather); their output, thus, becomes quite variable. This sharply contrasts with the diurnal humidity cycle’s source of energy, which is versatile, reliable, and can be applied easily to a large number of environments with utter disregard for either local weather patterns or geographic constraints.

Constructing pyridine-cluster channels

The membrane with a dense polycationic cluster configuration was developed by using a bottom-up technique, as shown in Supplementary Fig.  1 . Initially, a super-thin, high-density membrane was formed through self-assembly of a block copolymer (BCP). This BCP comprised a crosslinking polyisoprene (PI) segment and an ion transport poly-4-vinylpyridine (P4VP) segment. Following that, S 2 Cl 2 was used to crosslink the assembled BCP membrane, enhancing its mechanical robustness 34 . The BCP membrane, now sulfur-crosslinked ( s -BCP), underwent an acidification process. Concurrently, chloride ions were attached to the P4VP segment due to their electrostatic attraction. This process culminated in the creation of an ultrathin, dense, and durable ion channel membrane ( p -BCP).

The membrane thickness was measured using a cross-sectional AFM height image (Fig.  2a ), revealing an average thickness of ~74 nm. Supplementary Figs.  2 , 3 showed the nanostructural details of the BCP nanochannel membrane. The changes in chemical composition have been verified through XPS and FT-IR tests. Following the crosslinking with S 2 Cl 2 , the XPS spectra display signals for both Cl and S elements (Supplementary Figs.  4 , 5 ). To validate the protonation of pyridine, detailed XPS spectra for N and Cl elements were taken. As depicted in Fig.  2b , N 1s peak emerges at a higher binding energy of 401.2 eV, signifying the chemical linkage between N and Cl. The detailed XPS spectra for Cl elements validate the presence of chloride post-acidification, thus confirming the creation of the Cl clusters. In the FT-IR spectra, the intensity of the double bond peak diminishes post-crosslinking, and the pyridine peak transitions from 1598 to 1608 cm −1 due to its protonation (Fig.  2c ) 35 .

a Height profile for the p -BCP membrane, showcasing an approximate thickness of 74 nm. Inset: Sectional AFM height visualization of the p -BCP membrane placed on a silicon wafer. b Detailed XPS readings for N and Cl elements in both BCP and p -BCP membranes. c FT-IR readings for both the BCP and p -BCP configurations. d 1D GI-SAXS interpretation derived from the 2D GI-SAXS layout, highlighting the periodic design. e SEM depiction coupled with EDS traces for the p -BCP membrane. f TEM visualization of the p -BCP membrane, revealing the hexagonal alignment of the polycation clusters. Inset: AFM height depiction of the p -BCP structure.

The dense and regularly arranged polycation-cluster architecture is examined using GI-SAXS, SEM, AFM, and TEM methods. The 2D GI-SAXS pattern reveals a pronounced scattering void in the equatorial direction, signaling a regular vertical arrangement (Supplementary Fig.  6 ). Additionally, the 1D curve suggests a periodic distance of ~30.6 nm (Fig.  2d and Supplementary Fig.  7 ). The transmembrane ion-cluster channel structure is confirmed by the cross-sectional SEM image. The EDS patterns on the p-BCP membrane surface provide insights into its elemental makeup (Fig.  2e ), aligning well with the XPS findings. The distinct transmembrane cluster arrangement is further validated by the AFM and TEM visuals (Fig.  2f ). Post-acidification, the P4VP framework turns more water-attracting and swells due to electrostatic pushback (Supplementary Fig.  8 ). As a result, the super-thin, crosslinked membrane boasting dense pyridine clusters constructed nanochannels for selective transport of Cl − is successfully crafted.

Humidity-driven selective anion flux across membranes with pyridine clusters

We exposed the IL layer, which had a specific water content, to various humidity levels at 25 °C and measured the ion current. This was done to uncover the mechanisms behind the humidity cycle-induced ion current (Fig. 1 ). In Fig.  3a , we sealed the membrane in conjunction with two IL layer, which both have a water content of about 14.6%—this is balanced with an ambient humidity of roughly 50%. When the device was subjected to RH of 73% and 41%, the equilibrium I sc was found to be ~10.1 μA and −5.4 μA, respectively. This suggests that the ion flux direction can be changed by adjusting the surrounding RH.

a The change in experimentally measured I sc when subjected to surrounding RH values of ~73% and 41%. The IL layers’ water content is initially balanced with an ambient RH of about 50%. b Measured I sc mapped against the surrounding RH, ranging from as low as ~0% to as high as ~100%. c Equilibrium water content ( \({w}_{{{{{\rm{H}}}}}_{2}{{{\rm{O}}}}}\) ) in relation to different RH values from experimental measurement. d Simulated distribution of cation, Cl − , and water number density at the membrane-liquid interface, with the liquid being a mixture of ILs and water at varying concentrations. e Simulated comparative number density of Cl − ion, and cation with respect to water content, with an inset of the simulation model. The error bars represent standard deviations and n d  = 5 for each data point.

Extending our investigation, we exposed the device to a spectrum of RH values, spanning from ~0% to ~100% (Fig.  3b ). We found that increasing the difference in RH from the base 50% correspondingly increased the ion current. For instance, by raising the surrounding RH to 80%, the I sc climbed to 14.8 μA. Conversely, by reducing the surrounding RH to 32%, the I sc reduced to −9.9 μA. When the surrounding RH is set at 50%, the I sc gravitates towards ~0 μA. These findings emphasize that the ion current has a strong association with the surrounding RH. A greater deviation from the 50% RH mark augments the difference in water content across the membrane (Fig.  3c ), which in turn influences the ion current. Notably, this device works well under extreme humidity conditions, such as RH of ~0% and ~100% (Supplementary Fig.  9 ).

To better understand how the design of our device impacts the conversion of humidity changes into electrical current, we explored the effect of varying the thickness of the IL layer. We designed devices with the open IL layer thickness ranging from 2 to 1 mm, while maintaining the isolated layer at 2.0 mm. These devices were exposed to a relative humidity of ~73% at 25 °C to evaluate their responsiveness to humidity changes. The findings, detailed in Supplementary Fig.  10 , demonstrate that a reduction in the thickness of the open layer leads to a more sensitive response, as evidenced by the output current. Specifically, when the open layer thickness is decreased from 2.0 to 1.0 mm, the time required for the current to stabilize at an equilibrium value is shortened from ~35 to ~10 min. Additionally, the equilibrium current increases from 10.1 to 12.9 μA. This improvement is attributed to the decreased diffusion distance and enhanced rate of moisture absorption. A thinner IL layer means water molecules have a shorter path to travel from the air to the membrane interface, speeding up permeation and thereby boosting water absorption. Furthermore, this reduction in thickness increases the surface area-to-volume ratio at the interface where the air contacts the IL, allowing a greater portion of the IL to interact directly with ambient air, which accelerates moisture exchange.

To elucidate the origin of ion current, we examined the distribution of IL species at the liquid-membrane interface on a molecular scale, using full-atomistic molecular dynamics simulations. These simulations revealed that chloride ions Cl − readily penetrate the membrane’s inner regions, while cations predominantly remain in the liquid phase (as illustrated in Fig.  3d ). Additionally, we explored the impact of water content on ion distribution, observing in Fig.  3e that the average number density of Cl − and cations varies with water content. Notably, the number density of Cl − increases with rising water content and significantly exceeds that of the cations. We also investigated the diffusive behavior and properties of ILs through mean square displacement (MSD) analysis (Fig.  4a, b ). As water content increases, the self-diffusion coefficient (SDC) of Cl − rises more rapidly than that of the cations, indicating that Cl − diffuses faster than cations. The aggregation and rapid diffusion of Cl − within the membrane support our theory that Cl − plays a dominant role in the entire ion current generation process.

a Analysis of the mean square displacement (MSD) for Cl − and cations in systems with varying water content. b Evaluation of the self-diffusion coefficients for chloride ions and cations relative to water content. The inset shows the variance in self-diffusion coefficients between the two types of ions.

Hydrophobic interactions enhanced selective flux across pyridine clusters

Beyond our investigation of the membrane, we have also explored how the IL layers affect ion flux and ion current generation. The particular IL under scrutiny possesses a hydrophobic chain that is terminated by ammonium at both ends. These hydrophobic chains can cluster together to reduce exposure to polar or charged entities. Such a gathering of ions in the IL, termed ion clustering, results in them grouping together rather than distributing uniformly. This creates regions within the IL where ions are more densely concentrated.

To elucidate the impact of hydrophobic chain length on transmembrane ion movement, we synthesized three polyether amine fatty acid ILs: [PEA 230 ]Cl 2 , [PEA 400 ]Cl 2 , and [PEA 2000 ]Cl 2 . Protic ILs have good ionic conductivity due to mobile ions 36 , making them ideal for electrochemical devices like batteries and supercapacitors. So we use PEA ILs to reduce internal electrical resistance of the IL layers. In addition, PEA ILs is highly hygroscopic, absorbing moisture from the environment 37 , which is crucial for our device that generates ion flux through humidity cycles. Their polyether backbone also provides flexibility for varying ion transport, ensuring high ion selectivity. Additionally, they offer good thermal stability 38 , 39 . In contrast, common cations in aprotic ILs, such as imidazolium and pyridinium, cannot dissociate protons and lack these advantages.

The structures of these ILs were confirmed using 1 H NMR and FTIR spectroscopy, as illustrated in Fig.  5a, b , and Supplementary Fig.  11 . The 1 H NMR spectra revealed the disappearance of the –NH 2 peak at 1.48 ppm in PEA, replaced by a new NH 3 + peak at 8.13 ppm. Similarly, the FTIR spectra showed the characteristic –CH 2 and –CH 3 stretching vibration peaks at 2900 cm −1 , along with new peaks at 1460 and 1380 cm −1 corresponding to –CH 2 and –CH 3 groups. The peak at 1115 cm −1 was identified as the stretching vibration of the C–O–C bond. These findings collectively confirm the successful synthesis of the three PEA ILs.

a , b 1 H NMR and FTIR spectra of the ILs with n  = 2, 5, and 32. c Power density chart for ILs with n values of 2, 5, and 32, plotted against external resistances spanning from 1 to 10 6 Ω. d , e Overview of the peak power density and the associated I sc . f Equilibrium water molar ratio at an ambient humidity of ~73% at 25 °C. g The size distribution of cluster in ILs-water mixture system for n  = 2, 5, and 32. The error bars represent standard deviations and n d  = 5 for each data point.

Power density ( P d ) is widely recognized as the criterion for assessing energy harvesting potential. We integrated the aforementioned ILs into our apparatus and determined the output power density when subject to a constant ambient RH of ~73%. Initially, the water content in the isolated and open IL layers were both balanced with an air humidity of about 50%. We used the generator (with an effective area, A ) to power external resistive loads ( R e ) and recorded the resultant current ( I e ). As depicted in Fig.  5c , the power density, defined as P d  =  I e 2 R e / A , peaks with an R e of about 10 kΩ for IL with n value of 5. We would like to highlight that our device demonstrates a significant advancement in both power density and current density compared to other devices that generate electricity triggered by air moisture (Supplementary Fig.  12 ). Stability is another crucial factor affecting the practical application of our device. To evaluate its stability, we continuously monitored the I sc over a period of ~4 weeks (under the same condition with Fig.  3a , RH of ~73%). The results, presented in Supplementary Fig.  13 , demonstrate that our device can operate continuously for 4 weeks without obvious degradation in performance.

Additionally, we analyzed the variation in power density with respect to n , as illustrated in Fig.  5c–e demonstrating an optimal n value. The length of the side chains significantly impacts power generation: increasing n to 32 or reducing it to two both result in a simultaneous decrease in power density and I sc . Based on Fig.  5f , altering the length of the side chain, either by increasing or decreasing, leads to a reduction in the equilibrium water molar ratio. For n  = 5, the water-to-IL ratio stands at around 6:1. This is more than the ratios for n  = 2 (5:1) and n  = 32 (3:1). The capability to take in more water molecules contributes to a pronounced difference in water content across the membrane, bolstering selective ion flux and subsequently, a greater power output. In addition, as the IL absorbs more water, it enhances ion dissociation, thus increasing the number of free ions within the system. These liberated ions can move more freely throughout the IL and play a crucial role in increasing current generation, as a greater number of ions are available to engage in the transmembrane ion flux. This aligns with the operational mechanism depicted in Fig.  3b . Nonetheless, it’s worth pointing out that even though IL with n  = 2 exhibits a substantially higher water molar ratio than IL with n  = 32, their power densities and corresponding I sc values are contrary (Fig.  5d, e ).

We attribute the observed discrepancy to ion clustering, as depicted in Fig.  5g . Ion clustering is the phenomenon where ions in a solution come together to create bigger entities known as clusters. In our study, these clusters of cations arise due to the hydrophobic interactions linked to the length of the side chains. Specifically, [PEA 2000 ] 2+ shows a more pronounced propensity to aggregate compared to [PEA 230 ] 2+ , leading to the formation of larger cation clusters. The larger clusters with stronger charges experience significant electrostatic repulsion from the similarly charged polycationic membrane. This repulsion prevents the clusters from easily penetrating the membrane, thereby enhancing the overall current generation in the device.

Scalability of the polycation membrane for energy conversion and storage

Finally, we demonstrate the practicality and scalability of using humidity cycle-driven selective ion flux as a renewable energy source, by connecting this device in series or parallel. Initially, we constructed this device on microfluidic platforms (Supplementary Fig.  14a ). The design of this microfluidic chip includes two arrays of pores, separated by a central membrane. IL ( n  = 5) was infused into these pores, and a sealing membrane was used to isolate one side from the air, leaving the opposite side exposed. We introduced Ag/AgCl to measure the ion current. As shown in Supplementary Fig.  14b , we observed that when the pores (each 300 μm in diameter) are connected in parallel, they produce a short-circuit current of ~2700 μA. This result indicates that our device can be effectively scaled in a parallel arrangement. Additionally, we evidence that a single unit can efficiently charge capacitors ranging from 1 to 1000 μF in a brief period (around 2 min), as depicted in Supplementary Fig.  14c . Then, we engineered a circuit, shown in Supplementary Fig.  15 , which consists of 16 capacitors connected in series, designed for energy storage. This setup successfully generated a voltage up to ~2.21 V (Supplementary Fig.  14d ), sufficient to power a green LED requiring about 1.8 V. Collectively, these findings establish the potential of humidity cycles as a viable and eco-friendly energy resource, which is not heavily dependent on specific geographic or climatic conditions.

In conclusion, we have strategically utilized the daily variations in atmospheric humidity to stimulate a persistent ion current. We believe that this selective ion transport is facilitated by the polycationic membrane’s ability to effectively repel cationic clusters formed due to the hydrophobic interactions of alkyl chains, while concurrently permitting anion transportation. A singular device was able to achieve a substantial power density of ~405.9 μW/cm 2 . To demonstrate the practical application of this design, we integrated this device onto fluidic chips, which were then able to generate a voltage of ~2.21 V.

Looking forward, the capability to scale up these devices and integrate them onto fluidic chips opens the door to miniaturization and mass production. This holds promising implications for a myriad of applications, from powering remote environmental sensors to fueling wearable health devices 40 , 41 , 42 , 43 , 44 , 45 . The technology presents a virtually uninterrupted power source, a feature particularly beneficial for wearables that demand round-the-clock operation. Furthermore, this technology’s influence extends beyond just power generation. The humidity cycles’ ability to facilitate selective ion transport could provide valuable insights into nanotechnology, notably in specialized fields such as drug delivery systems and biosensing 30 , 46 , 47 , 48 .

Poly(1,4-isoprene)-b-poly(4-vinylpyridine) (PI 30,000 - b -P4VP 11,700 , Polymer Source, PDI = 1.06), polystyrene sulfonic acid sodium (PSS, Alfa, Mw = 70,000), sulfur monochloride (S 2 Cl 2 ), carbon disulfide (CS 2 ), acetone, and toluene (all from Beijing Chemical Reagents Co.) were utilized as received. PEAX (Poly(propylene glycol) bis(2–aminopropyl ether) with molecular weights of ~230, 400, and 2000 g/mol, is sourced from Aladdin. Additionally, hydrochloric acid with a concentration of 36.0% to 38.0% was acquired from Kunshan Jincheng Chemical Reagent Co., Ltd. All experiments were conducted using deionized water.

Preparation of the pronated block copolymer (BCP) membrane

The fabrication of the protonated BCP membrane began with the ultrasonic cleaning of a silicon wafer using acetone. Subsequently, a 4 wt% PSS solution was spin-coated onto the wafer at 3000 rpm for 1 min. The coated membrane was then dried under a nitrogen atmosphere for 30 min. Following this, a 2 wt% BCP solution in toluene was spin-coated onto the PSS layer to create the nanochannel membrane. Once fully dried, the membrane underwent crosslinking with S 2 Cl 2 vapor inside a sealed container. Excess S 2 Cl 2 and sulfur were removed using CS 2 . The membrane was then immersed in water to eliminate the PSS sacrificial layer. The final step involved protonating the crosslinked membrane in a 1.0 M hydrochloric acid (HCl) solution to enhance the charge density of the P4VP nanochannels, resulting in a self-standing ion-cluster channel membrane.

X-ray photoelectron spectroscopy (XPS)

Surface chemical analysis was conducted using a Thermo Scientific K-Alpha at a pressure of 5E-7 mbar, using a monochromatic Al Kα X-ray source ( hv  = 1486.6 eV). XPS readings were taken at normal emission at ambient conditions.

Grazing-incidence small-angle X-ray scattering (GI-SAXS)

The alignment of nanochannels and the periodicity of various membranes were verified using GI-SAXS. These measurements were performed using a Xeuss 3.0 system from Xenocs SA, France. The system utilized Cu Kα X-ray radiation with a wavelength of 1.5418 Å. Detection of the scattering signals was achieved with a Pilatus 300 K CCD detector by DECTRIS, Swiss, which has a 487 × 619 pixel resolution and a pixel size of 172 × 172 μm 2 . The detector was placed at a distance of 1800 mm from the samples and the grazing incidence angle was maintained between 0.2° and 0.3°.

Transmission electron microscopy (TEM)

The nanostructure of various membranes was examined using TEM techniques. Images were captured on a JEM-2100 TEM at an accelerating voltage of 200 kV. For sample preparation, a 0.5 wt% solution of BCP in toluene was deposited onto a copper grid. This membrane was then dried in a nitrogen atmosphere for 30 min. Post-drying, the polyimide phase of the s -BCP membrane was specifically stained using osmium tetroxide (OsO4) for 5 min to enhance visibility. Similarly, the P4VP phase of the p -BCP membrane underwent selective staining with iodine vapor for 20 min, which served to increase the contrast in the TEM images.

Scanning electron microscopy (SEM)

The structure of the nanochannels traversing the membrane was verified using a ZEISS Gemini 300 scanning electron microscope, equipped with a Schottky field emission electron source, operating at an acceleration voltage of 5 kV. The nanochannel membrane, after protonation, was placed on a silicon substrate. To reveal its cross-sectional structure, the sample was fractured in liquid nitrogen. The distribution of elements within the membranes was analyzed using SEM-based elemental mapping (Smartedx).

Fourier-transform infrared spectroscopy (FT-IR)

The cross-linking and protonation states of the membrane were validated through FT-IR analysis. These FT-IR tests were carried out using a Bruker Vertex70 instrument, which scanned in a range from 400 to 4000 cm −1 .

Contact angle

The surface wettability of prepared membrane surfaces was measured by the optical contact angle meter system (OCA40Micro, Dataphysics Instruments GmbH, Germany). At room temperature, 2 μL of ionized water was dropped onto the membrane surfaces. The contact angles were calculated by the tangent method.

Atomic force microscopy (AFM) detections

The surface textures and thickness of the membrane in air conditions were characterized using AFM. This was performed with a Bruker Dimension Icon AFM device utilizing ScanAsyst mode in air, with a scanning frequency of 0.977 Hz.

Preparation of the ILs

ILs PEA-Cl, specifically [PEA 230 ]Cl 2 , [PEA 400 ]Cl 2 , and [PEA 2000 ]Cl 2 , were synthesized using the acid-base neutralization method 49 . The process began by adding PEAX and hydrochloric acid into a round-bottom flask in a 1:2 molar ratio. This mixture was then stirred continuously at 30 °C for 24 h. After this period, the resultant PEA-Cl ILs were subjected to a drying process under vacuum conditions for 48 h at 50 °C, to effectively remove any trace amounts of water.

Characterization of ILs

The 1 H NMR spectra for the ILs were obtained using a Bruker AVANCE III HD 600 NMR spectrometer. The FTIR spectra of the ILs were recorded with a Thermo Scientific Nicolet iS50 spectrometer. For dynamic light scattering (DLS) analysis, a Malvern Nano ZS-90 particle size analyzer was employed, equipped with a 4.0 mW solid-state He-Ne laser, operating at a wavelength of 633 nm. Prior to analysis, all IL samples were filtered through a 0.45 μm hydrophilic polyvinylidene fluoride (PVDF) membrane filter to eliminate dust particles.

Molecular dynamics simulations

All the simulations employed Amber18 to explore the molecular mechanisms of humidity cycles driving ion flux across membranes 50 . The initial setup was created with the PACKMOL package, including 195 membrane molecules and 523 molecules of IL, specifically D400 polyether amine chloride 51 . Water content in the IL phase was varied to achieve concentrations of 14.6%, 18.5%, 22.2%, and 26.7% by adding different amounts of water molecules. The simulation box measured around 98 × 88 × 200 Å 52 . For water molecules, the TIP3P model was used, while the General Amber Force Field 2 described other species 46 , 52 . Simulations were conducted in the NVT ensemble at 298 K. Each simulation lasted 100 ns with a 2 fs time step. Analysis was focused on the final 20 ns of each run, where parameters such as density distribution and MSD were calculated.

Data availability

The data supporting the findings of this study are available within the paper and its  Supplementary Information . Other relevant data are available from the corresponding author on request.

Code availability

The calculations for selective transmembrane ion flux, as described in the Methods, have been processed and analyzed by the in-house software “ionic liquid database and analysis software” developed by the authors 47 , 48 , which are available from the corresponding author on request.

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Acknowledgements

S.Z. acknowledges financial support from the University of Hong Kong (2201100473). H.H. and Y.W. thank the funding from National Natural Science Foundation of China (22278401 and 22178344), and the independent research project of Zhengzhou Institute of Emerging Industrial Technology (ZZLX2022002). C.L. acknowledges funding from the Postdoctoral Fellowship Program of CPSF (GZB20230923), the China Postdoctoral Science Foundation (2024M754049).

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Yuanyuan Zhao & Yanlei Wang

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Beijing Key Laboratory of Ionic Liquids Clean Process, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China

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School of Energy and Environment, City University of Hong Kong, Hong Kong, China

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S.Z. conceived and led the project. Y.Z. designed the experiments and drafted the manuscript. Y.Z. and G.L. conducted the research. C.L. designed the membrane, Y.W., J.L., H.H., and J.Z. synthesized the ILs, conducted and drafted the simulations. Y.D., L.W., S.P., H.H., and M.W. contributed to this work by analyzing the data and revising the manuscript. Y.Z., J.L., and G.L. contributed equally. C.L., Y.W., J.X., and S.Z. supervised the project. All authors discussed the results and commented on the manuscript.

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Correspondence to Chao Li , Yanlei Wang , John H. Xin or Shuang Zheng .

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Zhao, Y., Liu, J., Lu, G. et al. Diurnal humidity cycle driven selective ion transport across clustered polycation membrane. Nat Commun 15 , 7161 (2024). https://doi.org/10.1038/s41467-024-51505-4

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A Waterspout Was Seen When a Luxury Yacht Sank. What Is It?

Witnesses reported seeing the tornado-like phenomenon hit the Bayesian, a sailing yacht that sank off the coast of Sicily on Monday.

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By Eve Sampson

What caused the sinking on Monday of a sailing yacht carrying the British billionaire Mike Lynch and 21 other people off the coast of Sicily is still unknown. But some attention has focused on observations by witnesses, who described seeing a small tornado-like column known as a waterspout forming over the water during an abrupt and violent storm as the vessel sank.

Fifteen passengers on the 180-foot yacht, the Bayesian, escaped on a raft before being rescued by a neighboring cruise ship. The body of the ship’s cook was recovered on Monday and six people remain unaccounted for , including Mr. Lynch and his daughter Hannah, according to officials with Sicily’s civil protection agency.

Prosecutors in the nearby city of Termini Imerese have opened an inquiry into the cause of the sinking.

Here is what to know about waterspouts, a surprisingly common weather phenomenon that may have helped sink the luxury yacht.

What are waterspouts?

Waterspouts are columns of spinning air and moisture — similar to tornadoes over water, according to the National Weather Service .

While some form in fair weather, and are aptly called fair weather waterspouts, another more dangerous variety called tornadic waterspouts develops downward from a thunderstorm. These tornadic waterspouts can either form as regular tornadoes over land and move out to sea, or form in a storm already over a large body of water, according to the National Oceanic and Atmospheric Association .

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Could a waterspout have sunk a superyacht?

These columns of spray, in essence sea tornadoes, can be highly dangerous.

D URING A SUDDEN nighttime storm on August 19th a superyacht sank off the coast of Sicily. There were 22 people on board the Bayesian , including Mike Lynch, a British tech tycoon, and his wife, who owns the yacht. The Italian coastguard has rescued her and 14 others; one passenger was recovered dead and six remain missing, including Mr Lynch and his teenage daughter. Witnesses say that the massive 56-metre-long vessel was submerged in a matter of minutes.

The Bayesian seems to have been a victim of extreme weather. But because it sank at night, it is not yet clear exactly what was to blame. One possible culprit is a tornadic waterspout, a weather phenomenon that occurs at sea, usually accompanied by high winds and waves. Waterspouts grow out of powerful thunderstorms, many of which have battered Italy this summer. Just how dangerous are they?

Waterspouts fall into two categories: fair-weather and tornadic. Both are columns of spray and mist connecting clouds in the sky with the sea. Fair-weather ones are weak, brief and form from the surface of the sea, climbing towards the sky with hot air. A tornadic waterspout, on the other hand, is in essence a tornado. Most tornadoes are formed by severe thunderstorms called supercells, during which hot air currents surge upwards while denser cold air falls. When those currents are exposed to differences in wind strength at different altitudes, they create a violently rotating vertical pillar that eventually touches the ground—or in this case, the sea.

Tornadic waterspouts can be very dangerous—but if one is indeed responsible for sinking the Bayesian , that would be highly unusual. If the column of wind is strong enough, it might push a boat’s mast so far sideways that the boat can no longer right itself. According to witnesses interviewed by Reuters, the wind seemed to push the yacht’s mast flat against the water. Boat designers and owners tend to like very tall masts, partly because they can make a vessel faster and partly because of the attendant prestige—at 72 metres, the Bayesian ’s was among the tallest aluminium masts in the world. This means that yachts often carry a lot of weight high up, making them less stable. But vessels of this kind are designed such that they should not sink even if their mast goes under water; their keel should provide a counter-weight that would right the boat.

That suggests that there were other problems—possibly portholes, hatches and the like left open. The Bayesian also had a retracting keel, allowing it to berth in shallow harbours: if it was drawn up during the storm, it would have lessened the leverage exerted against the force of the wind on the hull, mast and rigging. And the huge updraft of a waterspout creates an equally fearsome downdraft: that might have pinned the boat in its capsized position, allowing water to flood in.

Given the growing consensus among scientists that extreme weather events , such as storms and floods, are influenced by climate change, many observers might wonder if rare tragedies like these could become more common. But though the number of reported waterspouts in the Mediterranean has increased in recent decades, researchers believe this is in large part because of better surveillance. There is not enough data to be sure, but there seems to have been no marked increase since 2006, says Tomas Pucik, a researcher at the European Severe Storms Laboratory.

But it does not take a waterspout to make a bad storm dangerous. During both 2023 and 2024 oceans around the world have been freakishly hot. That can make storms more powerful and produce other worrying effects. One, a “downburst”, in which heavy, wet air plunges to the sea surface and creates strong surface winds that spread out horizontally, is another possible explanation for the sinking of the Bayesian . Marine inspectors may be able to find out exactly what happened to the vessel. Experienced sailors already know how unpredictable Mediterranean weather can be. Monday’s tragedy is a harsh reminder. ■

Correction (August 20th): An earlier version of this article said that Mike Lynch owns the  Bayesian . In fact his wife does. Sorry.

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