Chapter 15

1. Chapter 15 Water Resources

2. 15-1 Properties of Water

3. Why is water so important? • Essential for life, agriculture, and many industrial purposes. • All species must have water to survive. • We get essential materials from water. • We can receive toxic materials through our water supply

4. Properties of Water • Water has hydrogen bonds: (it is polar) • Water molecules have regions of charge causing water molecules to stick together and to stick to other materials. • Hydrogen bonds account for many of the other properties of water • Water molecules can move from place to place attached to each other – it flows. • Water exists as a liquid for a wide range of temperatures that exist on Earth. • Provides habitat • Liquid water can be found in most habitats on Earth.

5. Liquid water changes temperature slowly. • Acts as a temperature moderator • Areas near water often have smaller ranges of temperature variance than inner continental areas away from large bodies of water. • Climate of the west coast versus mid-west. • Acts as a heat/energy sink • Heat energy is absorbed by water and released over time. • Hurricanes occur in summer and fall because heat gained in spring and summer is accumulated as time passes.

6. Evaporating liquid water takes a lot of energy. (because of hydrogen bonding) • Condensing water releases a lot of energy. • Heat is transported, as well as moisture, as part of the hydrological (water) cycle. • Liquid water can dissolve a variety of compounds. • Many of the materials necessary for life are found dissolved in water. • Pollutants can be dissolved and transported in water. • Water filters wavelengths of the sun’s UV radiation protecting aquatic organisms from damage.

7. Water’s density changes with its temperature. • It is most dense at 0 C just before it freezes. • Cold water sinks, pushing warm water upward • Causes cycling of nutrients and other materials in temperate bodies of water (turnover) • Water expands and floats when frozen. • This allows liquid water to exist beneath the frozen surface. • Aquatic organisms can survive cold temperatures. • Liquid water expands when heated – thermal expansion. • On of the biggest problems with global warming/global climate change is rising ocean water. This is caused by thermal expansion of ocean water.

8. 15-2 Supply renewal and Use of Water resources

9. How much water is freshwater? • 97.4% saltwater • 2.6% freshwater • 1.984% Ice caps and glaciers • .592% groundwater • 0.014% Readily accessible freshwater

10. Freshwater supply is renewed by the hydrological cycle (water cycle)

11. Hydrological cycle terms • Precipitation – rain/snow • Infiltration – water that soaks into soil. • Runoff – water that moves over the surface – it doesn’t soak into the soil. • Evaporation – moisture that evaporates • Transpiration – moisture that evaporates from plants. • Condensation – gas vapor that becomes liquid in the atmosphere.

12. Surface Water • Surface water =water that doesn’t • Infiltrate the ground • Return to the atmosphere by evapo-transpiration. • Watershed/Drainage Basin – region of land from which surface water drains into rivers, lakes or other body of water. • What water sheds exist in our neck of the woods? • Reliable Runoff – amount of runoff that we can generally count on as a stable source of water from year to year. • About 2/3 of surface runoff is lost due to season floods.

13. Watersheds

14. Groundwater • Water infiltrates soil and percolates downward through voids (pores, fractures, crevices) in soil and rock. • Water in these spaces = groundwater • Groundwater near the surface (within 0.6 miles) contains more than 100x the freshwater of all lakes, rivers, streams and reservoirs.

15. Page 308

16. Groundwater terminology • Zone of aeration – pores in soil are a mixture of water and air. • Zone of saturation – pores are filled with water. • Water table – top of the zone of saturation – position changes (dries out = lower water table, more water = higher water table) • Aquifer – lower, water saturated levels of sand, gravel or bedrock through which water flows. • Unconfined aquifer – ground water without a confining layer of material, can easily mix with surface waters. • Confined aquifer – water beneath a confining layer, clay, that is kept away from surface waters. • Recharge – water the moves into aquifers by percolation or lateral movement from surface waters.

17. An overview of Chapter 15 Water Issues

18. Withdrawal • Removing freshwater for use. • Irrigation -70% • Most irrigation water comes from a different area than where it is used and doesn’t get returned to its origin • Industrial use – 20% • Use of water for steam, water is returned to source but can be warmer causing thermal pollution • Municipal (including homes) – 10% • What accelerates withdrawal? • Population growth – people require food and water.

19. Unequal Distribution • Water is not uniformly distributed throughout the world or even throughout some countries. • U.S. • Eastern US has plenty of water which is used mostly for industrial purposes. • Western US doesn’t have enough water, used mostly for irrigation

20. Western U.S. Water hotspots • See page 310 of your text

21. Too little water • Causes of water shortages? • Dry Climate • Drought • Dry Soil/Desiccation • Water Stress/Overuse of a reliable source

22. World Water Stress

23. Terminology • Drought- a prolonged period of time in which precipitation is at least 70% lower and evaporation is higher than normal. • Desiccation – exposed soil is dried due to exposure. • Water Stress – too many people using a limited but reliable water source. • Water withdrawal is higher than 20% of the reliable supply – can’t be recharged fast enough. • Water per capita drops below 1,700 cubic meters per year • Water Scarcity – water per capita below 1,000 cubic meters per year.

24. Unequal Access • 1 in 6 people worldwide don’t have access to adequate clean drinking water. • Even in areas of the world where there is plenty of water. • Why? Rural and poor

25. Ownership • Who owns water – it depends on where you live. • Eastern U.S. – water is public property. • Western U.S. – private ownership – person with water on their land owns the water. • Water from the tap comes from a public or private company that is paid to provide a clean, potable (consumable) resource.

26. Too Much Water • Flooding – caused by rain or rapid snow melt. • People who are most susceptible who live in floodplain. • Floodplain – an area alongside a river that periodically experiences flooding (typically flat with fertile soil) • Flooding is aggravated by • Urban development – paving surfaces that would otherwise absorb water • Deforestation of upland forests or coastal mangroves • Living in floodplain • Rising sea levels

27. Rising Sea Levels • Thermal Expansion • Melting Glaciers • People who live in coastal floodplains get the double whammy. • Flooding from upstream • Flooding from ocean

28. Water Contamination • Water pollutants come from a variety of sources (we’ll discuss more later). • Agricultural runoff • Urban runoff • Industrial waste and dumping • When water is contaminated, the contaminant has the opportunity to move, spreading even further.

29. How to Solve the Water Issues of the World • Variety of possible solutions, each with its own set of problems. • Dams and Reservoirs • Water Diversion projects • Groundwater removal • Desalination

30. Dams and Reservoirs • Large storage of water. • Provide water in dry areas from water rich areas upstream. • Provide electricity. • Control flooding downstream. • Consistent source of water for drinking and irrigation. • Significant changes to ecosystems/habitat downstream by removing silt and water. Impacts many wetlands (high in diversity and number of specie) • Takes water away from communities downstream (including other countries) • Damages land above dams where the reservoirs are created. • Displace people who live along river upstream of reservoirs. • Encourages people to live in areas that perhaps they should not. Pros Cons

31. Downstream cropland and estuaries are deprived of nutrient-rich silt Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Downstream flooding is reduced Provides water for year-round irrigation of cropland Reservoir is useful for recreation and fishing Can produce cheap electricity (hydropower) Migration and spawning of some fish are disrupted

32. Water Diversion • Water can be moved from one place to another by way of canals, tunnels, aqueducts or withdrawal from aquifers. • Move the water from “water rich” areas to “water poor” areas.

33. Water Diversion • Moves water to where it is needed. • Supplies drinking and irrigation water. • Allows people to live in formerly arid areas • Allow crops to be grown in semi-arid areas. • Causes environmental change to areas from which the water is removed. • Causes salinization of lakes as water is removed, allows for evaporation, leaving minerals behind. • Removes water from wetlands (high number and diversity of species) causing them to dry up. • Encourages people to overpopulate arid areas. • Causes water loss due to evaporation from canals. Pros Cons

34. Groundwater removal • Groundwater aquifers are renewable as long as the water isn’t removed faster than it is replenished.

35. Groundwater removal • Reliable source of drinking and irrigation water • Found almost everywhere • Available year round (not a seasonal resource) • Renewable if not depleted or contaminated • No evaporation losses • Relatively cheap to extract • Can be depleted • Can cause subsidence of land when water is removed • Polluted aquifers can be unusable for decades • Saltwater intrusion can occur in coastal areas • Reduces flow into lakes, rivers, streams, etc • Contamination can increase costs. Pros Cons

36. Saltwater intrusion Major irrigation well Well contaminated with saltwater Water table Sea Level Salt water Fresh groundwater aquifer Interface Interface Saltwater Intrusion Normal Interface

37. Desalination • Separating freshwater from dissolved minerals. • Uses a process called reverse osmosis • The cleaner the water needs to be, the more expensive the process. • Great idea – but it takes a lot of energy and money – relative to other ways of getting water.

38. So, what next? • All of the aforementioned solutions have significant negative impacts. • How can we get and use the water that is needed? Reduce water waste

39. Reducing water waste • Reduce water wasted through irrigation. • Redesign manufacturing processes to use less water. • Reduce personal water use. • Increase water prices – some people think water is too cheap.