Ch 10: Water: Hydrologic Cycle & Human Use

1. Ch 10: Water: Hydrologic Cycle & Human Use

2. 10.1 Water: A Vital Resource • 325 million cubic miles of water cover Earth’s surface. 71% of the surface. • 97.5% is salt water in ocean and seas • 2.5% is fresh water (contain < 0.1% salt) • 2/3 in glaciers and ice caps. • 0.77% of that in lakes, wetlands, and streams • Fresh water is a continually renewable resource.

3. 10.2 Hydrological Cycle: Natural Cycle, Human Impacts

4. Evaporation -> Liquid water turning in to a gas (water vapor) after absorption of heat. • Humidity -> Amount of water vapor in the air. -> Relative humidity: amount of water vapor air can hold at a particular temperature

5. Condensation -> The process of water vapor returning to a liquid form • Purification -> The process of evaporation and condensation purify water naturally.

6. Rain Shadow The dry region downwind of a mountain range.

7. Groundwater • Infiltration-runoff ratio: The amount of precipitation that soaks into the ground compared with the amount that runs off. • Watershed: All land area that contributes water to a particular stream, river, or major water body. • Surface waters: All waters on the surface of the Earth

8. Capillary Water: Water that held in soil. Returns to the atmosphere by evaporation or transpiration. • Gravitational Water: trickles or percolates down through pores and cracks through gravity. • Groundwater: the accumulation of gravitational water at an impervious surface.

9. Recharge -> Aquifers: layers of porus materials through which groundwater moves. -> Recharge area: area where water enters an aquifer 99% of all liquid fresh water found in aquifers

10. Purification -> Through percolation, bateria, soil and detritus are removed from water. -> Minerals are leached through percolation Natural exits for groundwater: • Seeps: water flows out over wide area • Springs: water exits the ground as a significant flow from a small opening.

11. The Human Impacts • Changing the Earth’s surface -> Floods • Climate Change • Atmospheric Pollution • Withdrawing water supplies

12. 10.3 Water: A Resource to Manage, a Threat to Control • Nonconsumptive Uses -> remains available to humans for the same or other uses if treated and enough supply Electric power 580 gal/day & Domestic use 164 gal/day • Consumptive uses -> water does not return to the water resource. Irrigation and other agri. use 485 gal/day

13. Sources • 40% of domestic water from ground water • 60% from surface water -> surface waters are susceptible to pollution • 90% of wastewater in developing nations goes in to surface water; UNTREATED • 1.7 million people die of contaminated water in dev, countries each yr. -> 90% are children

16. Surface Waters 75,000 dams are in the United States (at least 6ft in height)

17. Dam Impacts • Waterway below dam is deprived of water -> Impacts aquatic organisms -> Wildlife affected as well 95% mortality rate of juvenile salmon in the Columbia & Snake rivers

18. San Francisco Bay • 60% of fresh water that once flowed into the bay has been diverted • Irrigation in the Central Valley (4.5 million acres) • Municipal Use in S. Cali. (22 million people)

19. Groundwater • ¾ of all groundwater is non renewable • Saltwater Intrusion -> happens in coastal area through wells • Falling Water Tables -> withdrawal > than recharge • Diminishing Surface Water -> Wetlands, springs, seeps dry up due to falling water table • Land Subsidence ->The gradual settling of the land due to water table dropping -> Sinkholes

21. 10.4 Water Stewardship: Public Policy Challenges Obtaining More Water • More Dams to capture runoff -> Three Gorges Dam -> 500 dams have been destroyed in US -> Wild Rivers and Scenic Rivers Act 1968 • Tapping More Groundwater -> Tapping nonrenewable groundwater • Desalting Seawater -> Desalinization (Microfiltration & Distillation)

22. Using Less Water • Agriculture ->30%-50% of water used in irrigation lost to evaporation, percolation, or runoff (using current methods) ->Drip irrigation (reduce waste by 30%-70% & increase production) -> Surge Flow (computer controlled) -> Treadle pumps (allow irrigation during dry seasons)

23. Municipal Systems • 100 gallons per day used in homes • Flushing Toilets: 3-5 gallons per flush • Showers: 2-3 gallons per minute • Laundry: 20-30 gallons per wash • Xeriscaping: using desert plants that use little to no water • Recycling grey water (sink and shower water collected the used for watering lawns and washing cars.

24. Public Policy Challenges • Humans Use -> 26% of total terrestrial evapotranspiration -> 54% of accessible precipitation runoff -> Many players in the water cycle • Natural Water Policy • The Clean Water Act • Authorizes EPA to develop programs to protect the nation’s water quality

25. Key Issues • Water efficiency must be promoted as the primary strategy for meeting future water needs. • Water subsidies need to be reduced or eliminated. • Polluters must be charged according to their effluents. • Watershed management must be integrated into the pricing of water. • Water authorities must regulate dam operations as that river flow is maintained to simulate nature. • The U.S. must respond to the global water crisis with adequate levels of international development aid. • Much more research and monitoring are needed to provide the basic data for making informed policy decisions.