Water is everywhere. Water covers nearly 71% of Earth’s surface. It is in oceans, lakes, rivers, streams, glaciers, and icecaps. It is in our bodies, in animals, and in foods. There is freshwater and saline water or saltwater. Freshwater usually has a less than 0.1% salt concentration. Nearly all of Earth’s available water is in the ocean. Only a small fraction is freshwater. Our freshwater comes from glaciers, lakes, rivers, and streams. Let’s take a closer look at the distribution of freshwater and saltwater and how it is recycled here on Earth.

Earth is nearly three-quarters water. 97.5% of that is saltwater.

Only 2.5% is freshwater.

What is the distribution of Earth’s water? 96.5% of all Earth’s water comes from our oceans. While saltwater is not good for humans to drink, it does provide a habitat for many marine life animals.

Distribution of Earth’s Water

How is Earth’s water recycled? Water is constantly moving on our planet. It goes through different phases. This cycling is known as the water cycle. Throughout this cycle, water is constantly changing states from gas to liquid to solid. It begins with evaporation, when water from the oceans and freshwater bodies enters the atmosphere. Plants can also release water vapor to the atmosphere through transpiration. Evapotranspiration is the sum of evaporation and transpiration processes, releasing water vapor to the atmosphere. There it cools down and changes state to a liquid (condensation), returning to the Earth’s surface and the bodies of water during precipitation. Precipitation creates runoff. moving water over the ground surface and refilling bodies of water. It also infiltrates openings in the ground to replenish aquifers and moisten soil. During infiltration, seepage, groundwater discharge, and runoff, water also returns to fresh and saltwater sources where the cycle begins again.

Most of the freshwater on Earth is in the form of glaciers and ice caps (68.7%), leaving about 30% as groundwater. Freshwater found in lakes and rivers is what organisms use to meet their needs. Freshwater is used for drinking, transportation, heating/cooling, industry, and other purposes. We use freshwater for many things; therefore, it is important we do our part to be mindful of how much we use and conserve it.

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Water is a natural solvent and it mixes with pollutants easily. Not all of the Earth’s water is safe to drink, so it must be treated to make it drinkable. Freshwater is used for drinking, transportation, heating/cooling, industry, and other purposes. Water is treated at a treatment facility. These facilities remove contaminants that can cause serious illnesses. Water goes through a series of “cleaning” steps before it is safe for human consumption. It is not treated exactly the same in every community. A lot depends on where the water is coming from and how it arrives at the treatment facility. Americans use an average of 100 gallons of water per day. We use this water to flush our toilets, take showers, brush our teeth, cook, drink, water our yards, and the list goes on. With every American using that amount of water per day, it is easy to see how quickly our freshwater supply can diminish. It is important that we conserve, conserve, conserve or our demand will far surpass our supply.

Water treatment facilities clean millions of gallons of water daily.

Groundwater discharge

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This activity can be done as a class. You will observe a model of Earth’s distribution of water. For this activity, you will need the following materials: 5-gallon trash can, 2-cup measuring cup, 1-cup measuring cup, and a pipette/dropper. You will also need access to a water source, such as a sink or water hose. An abundance of water appears to be available here on Earth, but we can now see that only a tiny amount of that water is safe for drinking. Although water can be recycled, the amount of freshwater here on Earth will never increase. What we have is what we have, and we need to be conscious of how we use it so that our planet does not run out of it.

Earth’s Water

Total Freshwater

Glaciers and

icecaps

Groundwater Drinking water

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•  Your teacher will carefully fill the trash can with 5 gallons of water. The water in the trash can represents all Earth’s water, saltwater and freshwater combined.

•  *Two student volunteers will be called to the front of the class. The first volunteer will take the 2-cup measuring cup and carefully remove 2 cups of water from the trash can. These 2 cups of water represent freshwater. Do you remember where Earth’s freshwater comes from? It comes from lakes, rivers, streams, glaciers, and icecaps.

•  *Look at the remaining water in the large bucket. This water represents all of Earth’s saltwater. Can humans drink this water? No! Drinking saltwater will make us very sick.

•  *Take another look at the 2 cups of freshwater. One student will carefully pour a ½ cup of this water into the other measuring cup. The 1 ½ cups of freshwater left represents all of the water from glaciers and ice caps. Can we use this water? Why not? This water is not available for use because it is frozen.

•  *Where do you think the remaining ½ cup of freshwater comes from? That’s right! It comes from groundwater, runoff, lakes, streams, and rivers.

•  *Now let us take a look at how much water we can actually use for drinking. Your teacher will use a pipette/dropper to place one drop of water from the freshwater cup into the palm of a student’s hand. Out of the whole trashcan full of water, only one drop of water is safe enough for us to drink!

If there is no way to increase the amount of freshwater here on Earth, what are some ways we can conserve the freshwater we do have? Do you think we will ever run out? What do you think would happen to our planet and the organisms living here if we ran out of freshwater?

What Do You Know? Using the information you read about and the percentages that were given in the text, create a pie chart to illustrate the distribution of Earth’s water. Be sure to label and include the percentages in your chart.

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Importance of Water Conservation Our Earth is about 71% water. Of that percentage, about 97% is saltwater and 3% is freshwater. Because we cannot increase the amount of freshwater, it is important that we conserve as much as we can. For one week, you and your child will keep a record of the water you use each day. You can use estimates as you record. Include things like using water for cooking, showering, using the restroom, drinking, and so on. At the end of each day, compare your water usage with your child’s. Then, compare your records at the end of one week.

Discuss the following questions with your child: •  When do you use the greatest amount of

water? •  During which daily activities could you

decrease the amount of water you use? •  What are some ways you could decrease

your water usage each day? •  If everyone conserved the amount of

water they use, how could this help our planet?

Conserving water is something we should all strive to do on a daily basis. The process of taking salt out of water is very expensive and is not a common practice. We need, therefore, to save as much freshwater as we can so there is enough for future generations.

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