Water: A Global Resource

Have you ever thought about how much water it takes to make a pair of jeans? To produce a pound of corn? Or to make a car? What if you had a limited amount of water and had to decide how to “spend” your precious resource? A monopoly-style game developed by AmericaView, in partnership with NASA and USGS, to celebrate Earth Observation Day encourages you to find answers to those and other 'water use' questions.

This storymap contains three lessons designed to give you background on what we mean by 'water resources.' The lessons are also designed to stimulate your thinking about how we use, protect and monitor this precious, limited natural resource.

In the elementary storymap, U.S. rivers are the center of learning about water resources. This storymap, intended for middle school students, is designed to enhance knowledge and understanding about important river systems in other parts of the world.

Since the game poster utilizes amazing pictures of some important rivers, the first lesson introduces you to the technology that captures these images - LANDSAT!

The Incredible Landsat Program

Landsat Program is the greatest archive of our planet. It's a collaborative effort between NASA (National Aeronatics and Space Administration) and the USGS (U.S. Geological Survey). NASA is responsible for the launch while the USGS is in charge of operating, receiving, and archiving all of the amazing imagery taken.

The program provides the longest continuous space-based record of Earth’s land in existence. Landsat data give us information essential for making informed decisions about Earth’s resources and the environment.

Navigate through the Land Change with Landsat mission below to introduce yourself to Landsat images and how the Landsat satellites work. There are 6 sections to complete the mission. Click on this  link  to begin the mission.

1. Landsat in the World
2. Landsat's Orbit
3. Landsat's Key Numbers
4. 30-meter resolution
5. Landsat bands
6. More about Landsat

Now that you have learned a bit about Landsat and the imagery it provides, let's look at this imagery. First, view the high resolution aerial photograph of our nations capital with a few labels to help you identify land use features. Best to maximize your screen to see all the labels.

Next, take a look at the three Landsat images of Washington, DC. Each Landsat image is displaying the city in a different 3-band combination. The left panel is a natural color composite image (bands 4, 3, 2), the middle panel displays a false color composite image (bands 5, 3, 2), and the right panel shows the shortwave infrared composite image (bands 7, 6, 4). Notice how the colors of features like urban, forest, grass, and water appear as different colors depending on the bands displayed and the order the bands are viewed in the R, G, B (red, green, and blue) display components of your computer.

Now, see if you can identify the prominent features in the 3 images shown below. The images display southeast Delaware with the first image being a natural color composite - what our eyes see, the second a false color composite - shows green vegetation in shades of red, and the third image a single band (middle infrared band 5). Can you pick out these features in the following 3 images?

1. Cape Henlopen (sandy area jutting north out into the Atlantic Ocean)
2. Shopping outlets along Delaware Route 1 Highway
3. Forested areas
4. Agricultural fields (Can you see the circular center pivot irrigated fields?) and grassy areas
5. Bare soils
6. Wetlands

Now, let's apply what you have learned to identify features in an area you are very familiar with like your hometown or your favorite vacation spot. Given the Landsat imagery spatial resolution, it's best to zoom in to a scale of 1:75,000, about the size of a small county. Use the topographic map (on the right) to help orient yourself, and then find the same area in the 3 Landsat image composites below. Try to identify your town, forests and grassy areas, and water (lake, river).

Observations of the Earth from space gather information essential to forecasting the weather, assessing environmental hazards, managing natural resources, and improving our understanding of climate systems. Since the first satellites carried cameras into orbit in the late 1950s, space observations have grown richer as the instruments - termed sensors - have evolved. Consider the advantages of satellite observations...

We can systematically and frequently take pictures over the entire Earth's surface - the vast oceans, uninhabitable areas like the South Pole or Sahara Desert, and all the places where people live. And we can get pictures of very large areas.

Think about it... Ground, sea, and air-based observing systems that contribute to monitoring our planet are very important. But they have a major limitation — their view is limited. Consider a weather station. It's only measuring the weather of a very small area. Even though we have lots of weather stations in the United States that can be combined, we don't have data for every place. And, these kinds of observations are very limited in some parts of the world (much of Africa, parts of South America) and the oceans.

But from space, you can see the full picture.

Seeing beyond the visible: Imagery goes far beyond what our own eyes are capable of showing us with some sensors detecting energy beyond what is humanly visible. These sensors give us super-human ability to discover new views of our world. Take a look at one example of seeing beyond the visible displaying  vegetation moisture  in North Africa. This false color image shows dry and wet areas of vegetation moisture by looking at the near-infrared (band 5) and shortwave infrared (band 6) of Landsat 8.

Witness the world in action: Satellites continuously observe the Earth. The Landsat program has been observing the Earth since 1972. By combining images from across the span of time, we can visualize and animate to understand Earth's cycles and discover patterns. Check out the following three examples of imagery in action.

• Where is it raining? National Weather Service  current radar observations  show you where precipitation is falling.
• What's the weather forecast? Geostationary Observation Environment Satellite (GOES) imagery is critical for forecasting the weather. Click  here  to select any band, and then click on the Animation Loop. See where the sky is clear, or observe cloud systems swirling across the sky.
• Can we look at change over time? See this massive growth of Las Vegas over the past 50 years.

Now its time to test your skill as a scientist to identify the cause of changes to the Earth's surface observable from Landsat. See if you can get all questions correct!

Link:  https://eros.usgs.gov/remote-sensing-classroom/change-pair-game/ 

The Google Timelapse video below shows changes to the Aral Sea in Central Asia (Southern Kazahkstan and Northern Uzbekistan) over the period 1984 - 2016. Google Earth utilizes images generated by Landat satellites.

Before the 1960's, the Aral Sea was the world's fourth largest saline lake. It was fed by two rivers (Amu Darya and Syr Darya) rivers, which were diverted for agricultural irrigation. The consequences of these changes to important rivers systems are vast and have affected the lives of millions of people in and around the Central Asian region. It is for these reasons the "Disappearing Aral Sea" is a classic case study on human impact on water resources.

The interactive map below, created by ESRI for use in the Geoinquiry  Down to the Last Drop  uses satellite imagery as a basemap to help illustrate the extent of river dams and diversion on the rivers which feed the Aral Sea. The map also has a data layer that shows dams and canals on the Colorado River, and highlights the location of a few more drying lakes and rivers (Rio Grande in Texas, Indus River in Pakistan, and Lake Chad in West Africa). Click on Content to see the various data layers. Check the box next to each data layer name. The layer Aral Sea 2000 Image and 1960 Black Outline clearly show the rapid changes in the Aral Sea over the past several decades. Zoom in and out, click on Bookmarks to navigate around the map and see other features.

Explore a river or sea you are curious about by putting the name in the Search Bar on the upper right hand side.

Think, pair, share. Thinking about what has been happening to the Aral Sea, break into groups and brainstorm what might be occurring to Lake Chad (image to the right), a very important water resource in a semi-arid strip of land known as the Sahel. Read this  article from NASA Earth Observatory  to learn more about this critical water resource. Discuss in your group how the issues affecting Lake Chad are similar yet different to those impacting the Aral Sea.

You may think that every drop of rain that falls from the sky is 'new' water, but the water in every raindrop has been on the planet since the beginning of time, and has been moving around the plant, in the sky and underground, in various forms ever since the Earth was formed. That's one of the first things to understand about our precious water resources: The amount of water on the Earth is finite, meaning the total amount of water available always stays the same.

A second important point about water is that we can only use a small amount of that total water supply. Although the world’s total water supply may seem enormous, over 97% of the water on the planet is salty ocean water. Salt water cannot be used for drinking, irrigating crops, power plants, or other industries. All of these uses require fresh water supplies that only make up three percent of the world’s total water; and 2/3 of that water supply is frozen in Antarctica, Greenland, and alpine glaciers. Only 0.6% of the Earth’s water supply is usable as liquid and fresh water. This water is unevenly distributed in lakes, rivers, and underground. As the world’s population grows, the demand for water is also growing. We'll learn in Lesson Three some things we can do to manage our precious water resources more effectively. But first, we need to understand how water is always on the move.

The process that has water always on the move is known as the water cycle, also termed the hydrologic cycle. As it moves through the cycle, water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years.

One way to envision the water cycle is to follow a drop of water around, through, and above the Earth. But where do you start? Because the water cycle is a cycle, you can start anywhere along the cycle. How about you start in the ocean since that is where most of the Earth's water is found. Follow a drop from the surface of the sea by writing down as many components of the water cycle as you can with arrows that show the direction of flow of the water drop. Use the poster to aid your drawing.

How many components of the water cycle are you able identify in the diagram?

• In which parts of the cycle is water liquid?
• In which parts of the cycle is water vapor?
• In which parts of the cycle is water ice?

 Click HERE for an interactive version of this Water Cycle diagram .

• The sun provides energy to make the water cycle work.
• The sun evaporates water from the oceans into water vapor.
• Water vapor rises into the atmosphere, where the air is colder.
• Cold air causes water vapor to condense into water droplets and clouds.
• Water drops in clouds fall to Earth as precipitation in the form of rain or snow.
• When the precipitation falls as snow, the snow may pile up. If the snow gets deep enough, it compresses and becomes ice to form glaciers and ice sheets.
• When snow melts, the water flows into lakes, rivers, the oceans, and the ground.
• Rainfall on land flows downhill as runoff into lakes, rivers, and the oceans.
• Rain can also soak into the ground and, if deep enough, becomes groundwater.
• Water from lakes and rivers can also seep into the ground.
• Groundwater close to the land surface is taken up by plants who in turn transpire the water from their leaves - putting water back into the atmosphere. Some water goes very deep into the ground and stays there for a long time. Groundwater flows into the oceans, keeping the water cycle going.

Gather the items listed below:

• a plastic bag (1-2 Gallon bag)
• color markers (e.g. Sharpie Permanent Markers or any non-erasable markers)
• water
• blue food coloring (optional)
• packing tape

Draw the water cycle on the plastic bag. With adult supervision, warm up 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 bag and zip it up. Hang the bag upright on a window 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. After a while, water droplets appear on the inside of the bag. As they become bigger, they will eventually slide downward. The sliding down resembles the flow of water back into the sea.  If the water is still warm or if the bag is left on the window facing sunlight, it will keep cycling through the stages of the water cycle.

The role of rainforests in the water cycle is to add water to the atmosphere through the process of transpiration (plants release water from their leaves during photosynthesis). This moisture contributes to the formation of rain clouds, which release the water back onto the rainforest.

Where are the world's biggest rainforests?

The Amazon Rainforest is in South America, the Congo Rainforest is in Africa, the Australiasia Rainforests is in Oceana, and the Sundaland and Indo-Burma Rainforests are both located in Southeast Asia.

Moisture generated by rainforests travels around the world. Scientists have discovered that rainfall in America’s Midwest is affected by forests in the Congo. Meanwhile, moisture created in the Amazon ends up falling as rain as far away as Texas, and forests in Southeast Asia influence rain patterns in southeastern Europe and China. Distant rainforests are therefore important to farmers everywhere. When forests are cut down, less moisture goes into the atmosphere and rainfall declines, sometimes leading to drought.

There are some wonderful interactive resources that help us explore the planet. This interactive map from NOAA lets us zoom in and out and search anywhere on the planet. The web map opens with GOES GeoColor day and night imagery. Select also infrared, water vapor, or the latest JPSS VIIRS daytime global map.

When was the last time you visited a watershed? Guess what - you are standing in one right now!

A watershed is an area drained by a river and its tributaries. It can also be called a drainage basin. Every point of land in the United States drains into a river or a tributary, and evidentially into an ocean.

Some watersheds are sharply defined by the crest of a high ridge. Precipitation that falls on opposite sides of a mountain ridge flows in different directions. Watersheds in low elevation or gently rolling areas may be poorly defined, but can be identified by the flow of the rivers.

EXPLORE: Want to know what body of water is downstream from where you live?  Streamer  is a super cool interactive map that allows you to trace upstream and downstream water flow.

Click on GO TO MAP. Put your location in the (upper right hand) search bar to zoom to where you live. Select "Trace Downstream" tab, and then click on a stream near your home. See the trace downstream to where the stream flows. Click on "Map Contents" and see data about Real-Time Streamflow (zoom out to find streams that are observing streamflow) and Weather Radar. Be sure to zoom in and out and look at different scales. The Identify tool (on the top menu bar) provides more details about the stream. Click the tool and then click on a stream gage.

EXERCISE: Identify the Watershed You are Standing In

The map below illustrates the watershed boundaries in the continental United States. Each drainage area is considered a Hydrologic Unit (HU) and is given a Hydrologic Unit Code (HUC), the unique identifier for the area. For example, the very largest HUCs have 2 digits and are referred to as HUC 2s.

Using the interactive map below, find the watershed you are standing within. Use the Find dialog box to enter your location (enter address, city and state, or your known geographic latitude and longitude location).

If you dropped a bucket of water at your location, would those water droplets eventually flow into the Atlantic Ocean, Gulf of Mexico, Pacific Ocean, or a location with no outlet (This occurs in the desert southwest with some interior basins)? Use the topographic basemap to answer the question. First, find the nearest stream to your location, and then follow the stream downstream to where it joins a larger stream, and continue downstream to find the ocean the water drains into.

Do you remember the term 'runoff' from our water cycle diagram? As water flows over land, it collects soil and pollutants and carries them downstream. The Mississippi River drainage basin - one of the largest in the world, includes about 40% of the area of the continental United States! The Mississippi River and its many tributaries, run through many communities, and lots of agricultural land. This water, known as residential and agricultural runoff, is often full of pesticides and other pollutants that eventually empties into the Gulf of Mexico. Marine life can't live in polluted water, a situation known as a “dead zone.”

United Nations estimates that there are about 150 dead zones in the world as a result of agricultural development. Explore where these dead zones might be located using the interactive map below which was created for the ERSI Geoinquiry: DeadZones.

In the interactive map above, you started learning about major rivers on each continent. You also began to see where population centers are located (landuse data layer). Do you notice a pattern? Only 10% of the global population lives further than six miles away from a surface freshwater body, in most cases that freshwater source is a river.

The image below shows the location and size of the drainage basins of major global river systems. You should be very familiar with the fourth longest river - The Mississippi. We are going to learn a little bit more about the four rivers that round out the top 5.

EXPLORE: Brainstorm with a partner all the things you know about the following rivers:

• The Nile
• The Amazon
• The Yangtze
• The Yenisei

The Nile River is over 4,000 miles long and travels through Egypt, Uganda, Ethiopia, Kenya, Tanzania, Democratic Republic of the Congo, Rwanda, Burundi, Sudan, and South Sudan - not in that order - as it flows north to the Mediterranean Sea. Early civilizations thrived on the banks of its massive river delta at the mouth of the river made fertile by annual flooding. Floods are now largely controlled due to the Aswan Dam located in Egypt.

Most scientists label the Amazon River as the second longest river in the world (just under 4,000 miles and a couple hundred miles shorter than the Nile depending on how you measure), but all agree it has the largest drainage basin of any river on the planet. The Amazon River and its tributaries create a drainage basin for over 40% of South America. The river brings so much fresh water into the ocean that it desalinates at a distance of about 100 miles from the coast. The Amazon is well known for the rainforests that surround it, and which are estimated to produce as much as 20% of the Earth’s oxygen and provide habitat to about 2.5 million insect species.

The Yangtze River runs across central China, heading eastward as it flows into the East China Sea. It has been a major route for the movement of people and goods between east and west China for centuries. The earliest evidence of human activity on the banks of the Yangtze River dates 27,000 years ago. The Three Gorges Dam across the Yangtze River opened in May of 2006 and largest hydroelectric river dam in the world. The Yangtze river basin accounts for 40% of China’s freshwater resources, more than 70% of the country’s  rice  production, 50% of its grain, more than 70% of fishery production, and 40% of China’s GDP. Although some sections of the Yangtze are protected nature reserves, pollution from agriculture and industry continues to be a problem affecting the water and its ecosystem.

Yenisei River is the largest river system flowing to the Arctic Ocean measuring 2,540 miles long.  Yenisei River rises in the eastern slopes of the Khangai mountain range in central Mongolia and flowing northwards it eventually empties into the Kara Sea which is part of the Arctic Ocean. The river is a great source of hydroelectric power. A large portion of the Yenisei River remains frozen over much of the year. This river’s major headwater tributary Angara River drains Lake Baikal. A large part of the river is covered with taiga flora which is mainly composed of coniferous trees.

Did you notice how different each river and its landscape was in the images you previously viewed? Rivers and streams have a great impact in shaping the physical landscape. A river forms from water moving from a higher elevation to a lower elevation, all due to gravity. When rain falls on the land, some rain seeps into the land surface and rest flows across the surface as runoff. This surface runoff flows downhill into rivers and lakes, on its journey towards the ocean. Some of the water that seeps into the Earth forms groundwater. At a certain depth below the land surface, called the water table, the ground becomes saturated with water. If a river bank happens to cut into this saturated layer, as most rivers do, then water will seep out of the ground into the river. Thus, some of the water in rivers is attributed to flow coming out of the banks. This is why even during dry spells there is usually some water in streams.

Rivers are a mighty factor when it comes to shaping the local landscape. Flowing water continually erodes (cuts into) the land it runs through, and over millions of years the topography of the land can be greatly changed.

Rivers also transport soil and sediment from one place to another, which has a great impact on the landscape. When storms occur, they deliver large amount of rain and this rain bring along lots of eroded soil and debris picked up by surface runoff from the surrounding landscape and delivers to a river. Fast-moving water can pick up, suspend, and move larger particles more easily than slow-moving waters. This is why rivers are more muddy-looking during storms because they are carrying a lot more sediment than they carry during a low-flow period.

U.S. Geological Survey (USGS) measures both the amount of water flowing past a site (streamflow measured as discharge) and the quality of the water in terms of sediment and other useful characteristics. Both streamflow and the stuff in the water are continually changing. 

Exercise: Hydrology

Do you have a favorite stream or river to walk along? Have you asked yourself "How much water is flowing?" What is its water quality?" The USGS has been measuring streamflow on thousands of rivers and streams for many decades. Let's go to the  National Water Information System Mapper  and find out. Follow the steps below:

1. Enter your favorite stream by searching a place name, street address or zoom to it. Then, use the navigation tools (or your mouse) to find the stream. Does the stream has a gaging site? If not, select one nearby.
2. When the Site Information Pop-up appears, click on Access Data.
3. From this table, you can click on the "Current/Historical Observation" to see the surface temperature, discharge, and gage height, and "Peak streamflow" to find the highest streamflow each year.

This activity is based on  the River Puzzle lesson  from National Geographic.

BRAINSTORM all the ways people use the land in and around a river........

To help your brainstorming, name the activity captured in each of the pictures below. What other activities can you think of?

Speculate on how each of these different activities might impact the health of a river. Discuss your ideas with a partner.

Water is one of our planet’s most important natural resources. There is the same amount of water on earth now as there was when the earth was formed; there will never be any more or any less. Most of the world’s water supply (97%) is saltwater in the oceans and can't be used for our daily needs. Another 2% is frozen in ice caps and glaciers, leaving just 1% of the planet’s entire water supply in the world’s rivers, lakes, and groundwater to meet everyone’s water needs. Our homes, our farms, our cities, and our industries all depend on water. The video below will get you to think about all the different ways we use (and misuse) important water resources. 

Water is used in a variety of ways. We all need clean drinking water. A human can go weeks without food, but only days without water. Drinking water accounts for less than 1 percent of total water usage, but it’s one of the most important of all the uses. Clean water contributes to good health; contaminated water can cause disease and even death. In order to be clean enough for human consumption, water usually has to be "treated" in some way. 

We also need water that works for us, doing the dirty household jobs like laundry and cleaning and for growing gardens and keeping lawns green. Approximately 70 percent of the total household water usage is used inside the house, and of that amount 60 percent is used just in the bathroom. 

Beyond household chores are the heavy duty jobs in industry. Water is used in many industries. Agriculture is the second largest user of water in the U.S. water withdrawal, behind thermoelectric power. Farmers irrigate about 15 percent of America's farmlands to grow food and fibers. Just like crops, livestock need water, but this use accounts for a much smaller piece of the water withdrawal pie.

Power plants and steel mills use large volumes of water as coolant for their equipment. Water is the driving force in hydroelectric generation, which accounts for about 47 percent of all water use. Beyond its use in the production of goods, water is often used to transport those goods to market. Waterways are integral to national and worldwide shipping. Major and minor rivers are an important part of the transportation system, which allows people and goods to move quickly and efficiently around the country. The Ohio, the Hudson, the Missouri, and the Mississippi Rivers are some of our country’s hardest working rivers and they all play an important role in commercial navigation.

 One of water’s most popular uses is for recreation. Whether it’s swimming, water skiing, fishing, the water’s got to be clean. The recreation and tourism industry represents a large percentage of employment in the United States, and a big chunk of recreational spending comes from water-related activities.

Another use for water is habitat for wildlife. Water plays a major role in the life of any living thing. Plants, invertebrates, birds, fish, amphibians, reptiles, and mammals all depend on water. It is basic for survival. Many living things also need it as habitat for part or all of their lifecycle. Rivers, lakes, and oceans support entire diverse and fragile ecosystems. Ecosystems that can be shattered by even the smallest changes in water quality. 

A whole range of practices, the individual actions we take and decisions we make affect water quality. One person’s decision to properly dispose of paint keeps that paint out of a stream. One developer’s decision to control erosion keeps sediment out of a river. Multiply those individual decisions across an entire community, and you can see the impact proper practices can have. 

• What activities take place in your home or your school that can impact water resources?
• Make a list of the activites you brainstormed and try to identify if they help or hurt water quality.
• Why is water quality important?

Fun Fact: Did you know that agriculture accounts for approximately  40%  of our  nation’s consumptive water use . At a global scale, agriculture accounts for  69% of water withdrawl around the world .

• List 10 things you use every day (can be clothes, electronics, toothpaste, pencils.....)
• List 10 things you eat fairly regularly.
• Compare your list with a partner, identify things you both use and eat (hopefully you'll have at least one of each in common!)
• How much water do you think it takes to make or grow these items?

We already know that without water, life on Earth would not exist. Plants and animals all need water to survive. Our bodies need water more than anything else to function properly. Humans in general use a lot of water! We use water directly by drinking it, and by using it for cooking, cleaning, and bathing. We use it indirectly in virtually all the things we eat and use in a day. Pretty much everything you use in a normal day requires some amount of water for it to be produced. Everyday items like computers, smartphones, T-shirts, jeans, shoes, coffee, eggs, and dog food carry a water footprint. The  water footprint of a product  is the amount of water that is consumed and polluted in all processing stages of its production.

• A pound of almonds takes nearly 2,000 gallons of water to grow.
• A smartphone takes more than 3,400 gallons of water to produce.
• One bowl of dog food takes 200 gallons of water.

 Look at the images below. These are simple things we use every day. See how much water is required.  

CLASSROOM EXERCISE: Use this  online tool  to calculate your  Water Footprint    - an estimate of how much water you and your family use on an average day. Do your best to answer all of the questions. Be sure to ask for your water footprint when you reach the end of the survey. The final question asks if you want to learn more about Indoor Water Use, Outdoor Water Use, or Virtual Water Use. Select the area where you think you could find ways to conserve water.

•  Indoor Water Use  means our daily water use from the tap, toilet, shower, washing machine, dishwasher, etc. In U.S. this adds up to about 138 gallons/household per day (60 gallons/person per day).  Outdoor Water Use  is the water we use to water lawns, wash cars, fill the swimming pool, etc.  Virtual Water Use  goes unseen but is the water that is needed to produce the food we eat, the books we read, and the clothes we wear.

Compare your total water use with your classmates. Discuss why your answers may be so similar or different from your classmates, and ways in which you learned that you can use less water.

How much of your water footprint can you change?

With a partner, go back through the list. Talk about and write down any areas where you might be able to make a change and use less water. Conservation is a practice in which we use less of something. In addition to having and eating things that require a lot of water to produce, scientists estimate that 30-50% of the water in the United States is wasted. Letting the water run while you are brushing your teeth, taking really long showers (or too many baths) are some of the ways we waste water. One part of water management in which everyone can take part is water conservation--using only what is needed. Conserving water by using less helps to protect this important resource.

QUESTION: What things can you and your family to do conserve water?

Where does the water we use for every day activites (brushing teeth, washing hands and faces, quenching your thirst) come from? A simple answer is that it comes from the faucets in our homes and schools! But how does the water go from circulating though the water cycle to filling our sinks and bathtubs? And is all the water circulating through the water cycle safe for us to drink?

Think about all the things (big and small) that can end up in our rivers, streams, and lakes because of the many ways we use the land and other resources in our watersheds. How can we make sure our water is clean? Nature does some of the cleaning, but much of it happens in water treatment facilities.

Natural Water Filters - To think about how water gets 'cleaned', lets first go back to the water cycle and the travels of a water drop.

• evaporation - the sun's heat turns liquid water into water that moves through the air
• condensation - cooler temperature turn water vapor into droplets,
• precipitation - water droplets fall from the sky in the form of snow, sleet or rain
• runoff/percolation - water runs across the landscape and collects in rivers and lakes, in the ground, or gets absorbed by plants.

This natural cycle cleans water as it circles around – but most natural cleaning happens at the percolation stage. When water seeps into the ground, or get absorbed by plants, some of the harmful things (pollution and pesticides) that can get into the water supply are removed. Keeping plants and trees and green spaces will help make sure there are enough natural water filters.

QUESTION: Does your school have trees, grass or a garden that can help clean water when it falls from the sky as precipication?

Think about it...

Should cities and other urban areas plan for more natural filters? (Remember the Dead Zones created by argiculutral runoff that we looked at in Lesson Two).

More and more cities are creating parks, urban gardens,  bioswales , and small wetland areas to slow runoff and help percolation.

Look around your community and see how many of these green spaces you can find.

Water Treatment Facilities: Natural cycles are not the only way to clean water. The water that comes out of our taps (and runs down our drains) most likely goes though a water treatment plant. The water treatment process has a few key steps just like the water cycle.

• Aeration: the process of adding air to the water to help trapped gases escape
• Coagulation: the process of adding chemicals that act like magnets for dirt and other particles
• Sedimentation: the process of letting heavy particles sink to the bottom
• Filtration: the process of passing water through a filter to remove any last impurities
• Disinfection: the final stage of adding chemicals to kill any micro-organisms

Trace each of the steps on diagram below.

Download your own copy of the  game,  or contact AmericaView for a true Poster Sized version! Send feedback on what you learned once you've played to Dr. Tracy DeLiberty (tracyd@udel.edu)! We would love to get your feedback.

Put all that knowledge you learned in action by putting on a play to establish a new town in the desert. Act out the role water plays in all aspects of the process. Download the script at the  USGS Water Science School .