1. Chapter 21 Water Supply, Use and Management

2. Basic information Water has a high capacity to absorb and store heat. –Solar energy warms the oceans, stores huge amts of heat which transfers to the atmosphere producing weather Water is the universal solvent Water has a high surface tension Capillary Action of water Water is the only compound whose solid is less dense than its liquid form. –Ice floats Sunlight penetrates water to differing depths –Photosynthesis below the surface for both plants and photosynthetic animals

3. General Stats 97% of the earth’s water is in the oceans 2% is in the ice caps and glaciers 99% of Earth’s water in the natural state is unavailable or unsuitable for human use. Water is scarce in some parts of the world (ie: Middle East & N. Africa) U.S. Water Resource Council estimates that water use in the U.S. by 2020 may exceed surface water resources by 13%

5. Groundwater and Streams Define the following terms: groundwater, water table, recharge zone, discharge zone, vadose zone, aquifer, cone of depression, effluent stream, perennial stream, influent stream, ephemeral stream Copy Figure 21.2 – Neat and Colorful : ) Groundwater and Surface Water Flow System (Page 436)

7. Water Supply Depends on several factors in ;the hydrologic cycle –Rates of precip., Evaporation, transpiration, stream flow and subsurface flow Water Budget – the model used to balance inputs, outputs and storage and understand water supply

8. United States US:Avg water usage=100gal/person/day Europe: 50gal/person/day SubSahara: 5gal/person/day Ex: Missouri River flows at 8.4 trill.gal/yr –It could handle 230 mill Americans This is not considering precip, runoff patterns, Evaporation and droughts

12. Surface-Groundwater Interactions Withdrawal of groundwater reduces stream flow, lowers lake levels and can change the quality of surface waters. Can change a effluent stream from perennial to an intermittent influent stream. Diversion of surface water may deplete groundwater resources. (This may increase conc. Of dissolved chemicals in the groundwater due to lack of dilution from infiltrated surface water.

13. Groundwater Use & Problems Nearly 50% of people in US use groundwater as their primary drinking source – this accounts for 20% of all water that is used. In many parts of US – groundwater withdrawal exceeds natural inflow – OVER-DRAFT It can then be thought of as a non-renewable resource – It is being MINED –Causes damage to river ecosystems and subsidence

14. Ogallala Aquifer High Plains Aquifer – South Dakota to Texas 400,000 km 2 Tremendous amt. of groundwater, however in some areas it is being used at 20X the replacement rate Most severe area are ones in which irrigation was first used in the 1940’s WATER SHORTAGE !!!

16. Groundwater sustainability and management For groundwater : effective mgmt. for sustainability is long process. Withdrawal must be balanced with recharge Surface water is more easily managed: –Recharge is shorter As demand for water increases - so does MANAGEMENT To minimize water supply problems: –Locate alternative water supplies –Manage existing supplies better –Consideration to “out of the box” ideas Towing icebergs Importing water Permanent conservation methods Use reclaimed water

17. Water Use Off-stream use: –water removed from it’s source for use and then returned (industrial processes) Consumptive use – an off-stream use: water is consumed by plants or animals Must balance the amt. of water withdrawn with the health of the ecosystem In-stream use: –the use of rivers for navigation, hydroelectric power generation, fish and wildlife habitats and recreation Each use requires different conditions

19. Wetlands Areas that are inundated by water or where the land is saturated to a depth of a few centimeters for at least a few days per year Wetlands serve a variety of functions that benefit ecosystems and people

20. Natural Functions of Wetlands Natural sponge for water – During high river flow: store water, reducing downstream flow. Following a flood: slowly release water Groundwater recharge Primary nursing ground for many animals Natural filter that helps purify water Highly productive. Many nutrients and chemicals are recycled Buffer for inland areas Storage site for organic matter

21. Wetlands Wetlands are threatened in many areas 50 - 60% of wetlands in the US have disappeared in the last 200 yrs. –Diking & draining for agriculture –Leveeing –Filling in for building

23. Louisiana Wetlands http://projects.propublica.org/louisiana

24. Dam impacts

25. Pro’s and Cons of Dams

26. Benefits of Dams Water storage Flood controlFloods affected the lives of 65 million people between 1972 and 1996. IrrigationDams contribute to 12-16% of world food production. Electrical Power Generation19% of the worlds total electricy supply, in 150 countries. 24 countries depend on dams for 90% of their power supply. Improved navigationStabilized annual flows Improved domestic water availabilityIn 1990, over a billion people had access to less than the minimum required of 50 litres per person per day. RecreationFishing cab be improved esp. in lakes but also in rivers with introduced species, leisure (e.g., boating on lakes, extended rafting season on the Colorado River) EcologicalIncreased riparian vegetation if dam discharges are steady

27. Negative issues with Dams Ecological disruptionFragmentation of 60% of the worlds rivers; Disruption of movement of species (e.g., destruction of up to 75% of riparian bird species on the Colorado) Destruction of riparian vegetation if discharges are irregular, e.g., peak-power of flood control types of operations; loss of beaches and marshes Groundwater table effects Sedimentation behind dams Erosion downstream by sediment-starved waters Flucuation vs. steady releasesFlucuations strand fish, reduce habitat for larval native fishes; deny access to tributaries; Clogging of riversPeak floods required to clear channel may be eliminated

28. Canals Water is routed by use of canals or aqueducts. Water is deceptively fast in main canals: hazard for swimming Unanticipated environmental problems: –Ex: Nile River, Egypt –Snails that carry: schistosomiasis (Snail Fever)

29. Channelization and the Environment Channelization: –An engineering technique that consists of straightening, deepening, widening, clearing, or lining existing stream channels –Purpose: Control floods, improve drainage, etc.

30. Environmental Effects of Channelization Degradation of streams hydrology – loss of fish habitats Removal of vegetation – removes wildlife habitats Flooding downstream Damage or loss of wetlands – drains water Aesthetic degradation

31. Read & Summarize & Copy Read section 21.9, The Colorado River: Water Resources Management and the Environment Summarize in paragraph form or bullets Pages 453-458 Copy Figure 21.19 (page 456)

35. Sustainable Water Use The use of water resources by people in a way that allows society to develop and flourish into an indefinite future without degrading the various components of the hydrologic cycle or the ecological systems that depend on it

36. How can water be sustained? Develop water resources in sufficient volume to maintain health and well being Ensure minimum standards of water quality Ensure that human actions do not damage the long-term renewability Promote water-efficient technology Gradually eliminate water pricing policies that subsidize the inefficient use of water

37. Water Conservation Review the water conservation methods on page 444-445 of your text. Write down 5 conservation methods you had not heard of…..

38. Desalination as a Water Source Desalination: a technology to remove salt from water Reduce salt to 0.05% from 3.5% (sea water) Produce 5-8 million gallons per day Increased cost – several times that of traditional water supply Salty water is discharged from plants – affecting other ecosystems