3. Hydrologic Cycle

4. Aquifer—a body of rock or sediment that stores, filters, and transmits water through pore spaces and openings in the rocks

6. Henri Darcy, Dijon, France, 1855 Defined the term “hydraulic conductivity” to mean the ease with which a material transmits water.

7. K = hydraulic conductivity (m/day) I = hydraulic gradient (m/m) A = cross-sectional area (m 2 ) Q = discharge (m 3 /day) Darcy’s Law: K = Q AI

9. Artesian system—confined aquifer

11. Problems with groundwater withdrawal: 1.Overdraft—occurs when withdrawal from wells + natural discharge > recharge

13. High Plains (Ogallala) Aquifer

14. Center pivot irrigation 30 % of all groundwater withdrawn in US is taken from High Plains Aquifer, mostly for irrigation

16. Ogallala-- groundwater withdrawals for agriculture: 14 bgd total water withdrawals: 0.78 bgd Tennessee groundwater withdrawals: 0.03 bgd 5.5% of 0.2% of

17. Changes in the water table level in the Ogallala (1890-1999): MAP of Changes in Ogallala 1900-1980—avg. water table decline: 10 ft (max. 175 ft) 1980-2000— water table decline has slowed due to regulations and more efficient irrigation techniques

18. 2. Land subsidence lowering of land surface due to groundwater withdrawal

20. Venice, Italy— land subsidence, coastal flooding

24. Central Valley, Calif.— land subsidence

25. Mexico City

27. abaondoned well casing, Mexico City

29. Karst—terrain having unique characteristics of relief and drainage due to dissolution of carbonate rocks (limestone, dolomite) Special problems with groundwater:

31. landfill cave stream Karst aquifers are typically not good filters of groundwater pollutants

32. Winterpark, FL “Oh no, my truck!”

33. Collapse sinkhole in Cookeville

34. TOTAL FRESHWATER WITHDRAWALS, 1995

35. Groundwater withdrawals and uses in the US (2000) million gallons Use per day (bgd) % Irrigation 56.969 Public supply16.019 Industry 3.6 4 Other 6.6 8 Total83.1 100

36. Fig. 4.2 Miss. R. aquifers (15%) High plains aquifer (30%) California, Central Valley and western basin aquifers (10%)

37. Water resources of Tennessee % Tennesseans that rely on public water 1960……68% 1995….. 84% TN -- Total water withdrawals: Surface water (rivers, reservoirs): 96% Groundwater: 4%

39. East TN: some high-producing aquifers in areas of fractured bedrock Middle TN: poor aquifers due to low-porosity, dense limestone bedrock West TN: very productive aquifers, sand and gravel deposits

40. Note high withdrawals from TVA reservoirs. These supply major cities and provide water for steam plants.