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Water Resources & the Technologies We Use to Harness Them

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Presentation on theme: "Water Resources & the Technologies We Use to Harness Them"— Presentation transcript:

1 Water Resources & the Technologies We Use to Harness Them
Title slide Water Technologies Thinking with Data: Science Part 2

2 Why is water necessary for life?
Discussion Question Why is water necessary for life? TEACHER GUIDELINES: Engage students to think of all of the uses of water. As they think of all of water uses, they will begin to build an appreciation of the importance of water in our lives. It is likely that they will create a much larger list than the following slide, adding more detail than the general overview of water uses.

3 TEACHER GUIDELINES: Clean water is needed for these four major areas
TEACHER GUIDELINES: Clean water is needed for these four major areas. Sanitation refers to the ability to provide adequate sewage disposal that separates sewage waste from drinking water supplies. Disease in a community is highly correlated with a lack of public sanitation. Though sanitation tends to be an issue in more water scarce countries, students should be made aware that the protection from mixing sewage with drinking water has significant costs. There are some areas in the United States that suffer with this type of water pollution.

4 What percentage of all of the water on earth is fresh water?
Discussion Question What percentage of all of the water on earth is fresh water? TEACHER GUIDELINES: Encourage students to guess. The more students wonder about this question, the more they will remember the answer in the following set of slides!

5 TEACHER GUIDELINES: Slides 3, 4, and 5 show the distribution of water globally. Many students do not know that most of the world’s water is salt water (undrinkable and/or unusable for agriculture). The green box shows a graphical depiction of the amount of fresh water relative to salt water, globally. Optional discussion question: Why can’t we use salt water to drink or for agriculture? Some students do not understand why we cannot drink salt water. Department of Energy’s scientist, Prof Bill's, explanation of why we cannot drink salt water is brief and to the point: “Humans can’t drink salt water because the kidneys can only make urine that is less salty than salt water. Therefore, to get rid of all the excess salt taken in by drinking salt water, you have to urinate more water than you drank, so you die of dehydration.” Why can’t salt water be used for agriculture? In general, too much salt will interfere with the chemistry in a plant that allows the plant to make food and to obtain energy from food. In addition, plants usually get their water through their root system by a process called osmosis (students who have had biology will know about this process). Osmosis involves the passage of water across the membrane of a cell from an area of greater concentration to an area of lesser concentration. If the plant is surrounded by salt water, the plant will tend to pass fresh water from their inside structures to the soil through the roots, causing the plant to lose, not absorb water. There is a type of plant, called halophytes, that have special structures that separate the salt in such a way that it is prevented from mingling with the rest of the plant, allowing the plant to survive in a salt water environment.

6 TEAHCER GUIDELINES: This slide shows that the majority of fresh water available is in ice caps and glaciers, more than 75 times as much fresh water is stored as ice than is available in lakes and rivers. And more than 30 times the amount of water available on the surface is stored in the ground. This is quite amazing and you might want to make sure students understand it. Perhaps have them think about all the rivers and lakes on earth and then imagine 70 times that stored as ice. Notice, however, this is nothing compared to the salt water in oceans.

7 TEACHER GUIDELINES: This slide shows where surface water is stored – mostly lakes. It might be interesting to point out that ¼ of the world’s lake water is held in the Great Lakes system. It is interesting to note that water withdrawals, globally and in the US, come roughly 80% from surface water and 20% of groundwater.

8 What is the Trend in Global Use of Our Fresh Water?
TEACHER GUIDELINES: This graph depicts, globally, how much water is used by the domestic, industrial, and agricultural sectors over the last century. It is important to note that agriculture is, by far, the greatest consumer of water. This graph parallels the overall increase in human global population as well. Students should understand that the more the population increases, the more water will be consumed.

9 Where Do We Get Our Fresh Water?
TEACHER GUIDELINES: Encourage students to guess. This slide pictures ground water, rivers, swamps, and lakes. It is meant as a transition from where we find our fresh water to looking at the technologies that we use to gather, clean, and transport fresh water to the places we need it.

10 Discussion Questions If most of the surface water is in lakes and rivers, how can we get the water to places where people live and grow crops? And, if most of the available water is stored underground, how can we get that water to the surface so we can use it? TEACHER GUIDELINES: Let the students talk about possible ways water can be transported by natural lakes, rivers, and groundwater.. Later after the students talk, review what they said. They should mention technologies like dams and irrigation channels and wells.

11 Dams TEACHER GUIDELINES: This is the Mosul Dam in northern Iraq. It holds 12 cubic kilometers of water and the lake it produces covers 225 square miles.

12 What Dams Do Store water during the rainy season
Control periodic floods TEACHER SCRIPT: Dams create an artificial lake (a reservoir) by building a wall that allows the river’s water to remain in the lake area defined by the dam. Most dams periodically release water to the river bed on the other side of the dam. Two of the major purposes of dams are to store water that can be used during times of draught, and to control periodic flooding. They do this by containing the periodic overflows during the rainy season with the dam made lake.

13 What Dams Do Produce electrical energy
TEACHER SCRIPT: When you store all that water in one place, you also have the power to create your own giant waterfall, and there’s lots of energy in a waterfall that you can put to useful purposes. In this animation, you can see how the energy from the fake waterfall created by the dam turns a giant turbine that, in turn, creates lots of energy for electrical power.

14 What Dams Do Provide recreation areas (fishing, boating)
Redirect river water to new locations for farming and domestic use TEACHER SCRIPT: People use the lakes created by dams, the reservoirs, for fishing and boating. A very important use of dams is to redirect water so that it can be used for farming.

15 What do you think are the most important uses of dams?
Discussion Questions What do you think are the most important uses of dams? Do you think that dams can cause any problems? If so, what might they be? TEACHER GUIDELINES: This slide is important to stimulate students to think about dam uses. If they have to decide what the most important function of a dam is, they will better be prepared mentally to tackle the more challenging issues presented in the next few slides. Encourage students to defend/explain their answers. Encourage students to think about the problems dams might cause. Be supportive of all answers. If they can begin thinking about the potential problems dams could cause, they will be better prepared to compare their answers with those of the next few slides and hopefully be more receptive to learning and thinking about potential problems with dams.

16 Problems Caused by Dams
TEACHER SCRIPT: This is a huge problem. The big science concept behind the next few slides is evolution. Over tens or hundreds of thousands of years, living organisms evolve to adapt to their environment. Individuals who do not have features that help them to survive (get food, hide from predators) tend not to survive long enough to reproduce. Those individuals that do have characteristics that are better at helping them to survive, have a better chance of passing their traits to their children. Some examples will be provided in the next few slides. The types of plants and animals that live in the river and the wetlands next to the riverbank have evolved physical and/or behavioral characteristics that help them to survive in that specific environment. If the environment changes, the characteristics that helped them to survive may not help them in the changed environment. It is estimated that dams have been the cause of extinction of about 20% of the varieties of fish living in the rivers. The impact on other animals and plants living in and around a river than has been dammed is similar. This is a real world instance of a very important idea in science that they will be learning further about as they continue in their education. Dams change the pattern of the rivers’ natural cycles. The new patterns may not provide the food and shelter needs of the plants and animals living there.

17 Discussion Question Dams stop flooding. What kind of problems might occur if floods are stopped? TEACHER GUIDELINES : Again, the students are stimulated to think about problems cause by preventing floods. This is not a usual way of thinking. From a ‘people’ perspective, flooding can be very destructive to houses and other structures built too close to the banks of a river. People living in those houses are effected by floods. That is our usual perspective. Thinking about potential positives of flooding is much more difficult.

18 Problems Caused by Dams
Floods take nutrients from the land to the rivers. Animals who live in or by the water often coordinate their reproductive cycles with flood seasons so their young have food to live. TEACHER SCRIPT: In a river’s natural cycles, flooding its banks after a particularly heavy rainfall, is a periodic event.The flood waters will soak in nutrients from the surrounding land. When the waters retreat back to the river, they will be replenished with nutrients from the soil. These nutrients help to sustain the plants and animals that live in the river and riverbank ecosystems. One of the major adaptations of animals is to coordinate their reproductive cycle to a time that the rivers are rich in nutrients. (*Note: this is not a ‘willful’ adaptation. The animals who reproduce during this time have a offspring with a better survival rate than animals who reproduce during other times. The survival rate is directly proportional to the availability of food for the young, in this case. The genetic behavior to reproduce after the flood season is passed to their offspring, who will likely also reproduce after the flooding season. This exemplifies the ‘survival of the fittest’ idea.) Dams disrupt this natural cycle.

19 Problems Caused by Dams
Floods also deposit rich silt onto the flood plains, creating nutrient rich land for agriculture. TEACHER SCRIPT: The flowing of nutrients from the land to the river works both ways. During flooding, the river dissolves some of the nutrients from the land. At the same time, silt particles, also rich in nutrients, settle out of the water onto the land. During this exchange, the river gets additional nutrients found primarily on land, and the land gets additional nutrients found in the silt. The plants and animals in the water and on the land both benefit. Dams stop the renewing of the land through silt deposits

20 Silt Normal silt Silt is trapped and builds up behind the dam. The water released by the dam is without silt. Silt consists of very small particles of dirt and rock. Normal river water carries silt. When river water is trapped by a dam, the silt is deposited on the bottom and builds up behind the dam. The water released by the dam has no silt. TEACHER SCRIPT: There are two more dangers related to silt. Dams are typically built to have the capacity to trap a specified amount of water. That means that the pressure of holding all of that water will not crush the dam. They do not take into consideration the additional pressure caused by silt. As of now, we do not have cost-effective technology to remove the silt from behind the dams. Secondly, when the water is released by the dam, it is released by a part of the water that is “silt free”. This fast moving water that is released proceeds to “scour” the river bottom, picking up existing silt and transporting downhill. What remains is water free of the natural silt, sediment, and debris, and these things provides nutrients and shelter to the animals that live in the water. The aquatic ecosystem (the river below the dam) can be altered so drastically that it no longer can support life.

21 Problems Caused by Dams
TEACHER SCRIPT: Unlike a flowing river’s natural cycles, dams release much more water at infrequent intervals into the riverbed. In the downstream side of the dam, the river is greatly diminished by the dam holding the river water back. Periodically, water is released from the dam into the riverbed. Water from the reservoir has temperature zones. The water is warmest at the top and coldest at the bottom. Water released from dams is typically released from the bottom of the dam. The water is quite cold compared with normal river water. Plants and animals have a range of temperatures in which they can survive. Often, the water released from dams is too cold for some of the river organisms. Another characteristic of a healthy river is the silt present in the rivers, the sand, and the woody debris from the surrounding plants. The silt provides nutrients, the sand and debris provide a habitat to which the river animals are adapted. Without a rich nutrient base and without a place for river animals to live, their environment is no longer suitable for survival. If the dam releases water once in a while, the high energy and coldness of the sudden floods picks up and removes silt, sand, small animals, and woody debris. A healthy living river needs the sediment and warmth to provide a habitat for animals.

22 TEACHER SCRIPT: For example, these river otters need the debris from fallen branches or trees for their homes.

23 Discussion Question Is it better or worse to have dams?
TEACHER GUIDELINES: There is no easy answer to this question. This is a real-world issue, however, that students will need to think about. This short examination of the effects of dams on the river ecosystem will help students to think about what types of damage that dams could cause to the environment. Some scientists are saying that more we can engineer our dams to provide the flow of water to the interrupted river in as natural a way as possible, the healthy the river ecosystem.

24 to go, let us take a closer look at
Before we look at the technologies designed to get our fresh water to the people and the places it needs to go, let us take a closer look at our major source of fresh water - groundwater TEACHER GUIDELINES: This slide is intended as a transition slide to begin to look at the technologies that transport fresh water from underneath the ground to the surface. First, it is worth a look to see exactly what groundwater means, since it accounts for most of the fresh water in our earth. It also accounts for 20% of the overall water withdrawal, surface water making up the rest.

25 What is Groundwater? TEACHER SCRIPT: We all know what surface water is. That’s the stuff we see around us. But what is groundwater? It’s the water underground. It’s water stored at different depths. Sometimes it is not too deep underground, sometimes it’s very deep. It is stored in different kinds of geologic or rock structures. In this diagram, you can see the land surface, and then if you dig into that land, you will first hit a zone that’s not “saturated” by groundwater. It might occasionally be saturated by rain, but in the dry times, it’s pretty dry. Then, if you keep digging, you get into some softer, muddier soil. That’s called the saturated zone. That’s where the water stored underground begins. The top of that zone is often called the water table because the top of the water stretches underground like the top of a table. People have been digging into the ground to get to this groundwater for a very long time. What do we call the holes we dig to get to groundwater?

26 Wells TEACHER SCRIPT: In dry areas, people have tapped into groundwater by digging deep wells. You can see the path of wells in the picture above and you can see a well in Syria under construction in the picture below. Wells, unless natural (artesian) must have pumps that will lift the water from underneath the ground to the surface.

27 What Wells Do Tap groundwater for drinking and irrigation.
TEACHER GUIDELINES: Just reiterate what wells do to be sure students “get it”.

28 Problems With Wells Wells may deplete a nonrenewable source of groundwater. If the groundwater that the well is drawing from is contaminated, the water used for drinking or agricultural will also be contaminated. TEACHER SCRIPT: Wells account for a large proportion of the fresh water (about 20%) that is used for drinking and agriculture. The problem occurs when the withdrawal from the underground aquifer occurs at a rate that is greater than it fills up from the rains, it is considered to be a nonrenewable resource. The water may be in danger of being depleted. Another issue is simply the same issue of pollution contaminating our fresh water. If the ground water is polluted, the water that is pulled out by wells will be polluted as well.

29 Irrigation Canals TEACHER SCRIPT: About 20% of the total fresh water withdrawal in the US is ground water. The rest is from surface water. This water is largely used in irrigation canals for agriculture. Over the next few days we will focus our study on irrigation canals – their positives and negatives. For now, it is clear that we need some way to get water from lakes and rivers, or reservoirs and wells, to where we need it. The oldest technology we have for doing that is irrigation canals

30 Discussion Question What kinds of problems might interfere with us having all of the fresh, clean water that we need? TEACHER GUIDELINES: This is just intended as a brainstorm. Students will be investigating this set of problems later in the week. For now, let them brainstorm some ideas You could record student ideas on the board and then go onto the next slide (or skip the next slide altogether). Alternatively you could just take student ideas and then go onto the next slide.

31 What Can Cause Problems With Our Current Water Supplies?
Water Availability Uneven distribution of water resources Changing (and growing) population Dams Different climates in different regions Water Sharing Who decides what is fair? Water Pollution Salinity Industrial pollution Urban stormwater sewage Shipping Mining Agricultural TEACHER GUIDELINES: These are some examples. Students will be studying some of these issues over the next several lessons. The slide is animated to bring up big categories one at a time so you need to click for each to appear. You may choose to use this slide in conjunction with the previous, or to skip it and brainstorm with students on the board.

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