Week 10 Weekly Assignment Groundwater1

Week 10 Assignment (20 pts) N ame:___Mercedes Garcia_____________________________ CHAPTER 11: GROUNDWATER AND WATER RESOURCE Important Concepts 1. Water can be considered a renewable resource; however, there is relatively little fresh liquid water in the hydrosphere. Most of the fresh water exists as ice, mainly in the polar ice caps. 2. Subsurface water is all the water occupying pore spaces in soils and rocks below the ground surface. Ground water is subsurface water that exists below the water table within the zone of saturation ; soil moisture is the subsurface water contained in unsaturated soil layers. 3. Recharge is the process of infiltration and migration through which groundwater is replenished. Urbanization and the filling in of wetlands can reduce groundwater recharge. 4. An aquifer is a rock unit that is sufficiently porous and permeable to be useful as a source of water. Porosity is the proportion of void space in rocks or soils; permeability is a measure of how readily fluids flow through interconnected pores and cracks in the material. 5. An unconfined aquifer is an aquifer directly overlain by permeable rocks and soil. A confined aquifer is bounded above and below by impermeable layers ( aquitards or aquicludes ). Artesian conditions exist when water in a confined aquifer rises above the apparent water table because of hydrostatic pressure. In an artesian system, the potentiometric surface represents the height to which the hydrostatic pressure would raise the water if the water were unconfined. 6. The consequences of ground water withdrawal include lowering of the water table, compaction of aquifer rocks, ground subsidence, sinkhole formation, and saltwater intrusion. 7. Commonly used indicators of water quality are the concentrations of a dissolved chemical species (commonly expressed as parts per million, ppm, or parts per billion, ppb), concentration of total dissolved solids (TDS), pH (a measure of acidity), hardness, identification of impurities, and presence of naturally occurring radioactive elements. 8. Americans divert about 400 billion gallons of water from the hydrosphere each day. About 100 billion gallons of this total are consumed (not returned to the hydrosphere as wastewater). Most consumed water is lost to evaporation. Agriculture, by diverting water for irrigation use, is the largest consumer of water. 9. Methods of extending the water supply include conservation, interbasin water transfer, and desalination. Interbasin water transfer is politically sensitive, and both this method and desalination are expensive and pose environmental problems. 70

Key Terms Multiple Choice (0.5 pt each) 1. Excluding the oceans, the largest reservoir of water in the hydrosphere is a. ground water. b. lakes and streams. c. the atmosphere. d. ice. 2. The largest reservoir of unfrozen fresh water is a. ground water. b. lakes. c. streams. d. the atmosphere. 3. Which one of the following rocks would most likely have both high porosity and high permeability? a. shale b. slate c. granite d. sandstone 4. Soil moisture is found a. within the zone of saturation. b. within the vadose zone. c. within the phreatic zone. d. below the water table. 5. In an unconfined aquifer, the top of the zone of saturation is called the a. potentiometric surface. b. water table. c. saturation limit. d. water level. aquifer aquitard artesian system cone of depression confined aquifer desalination ground water hard water karst topography permeability phreatic zone porosity potentiometric surface recharge saltwater intrusion sinkhole soil moisture unconfined aquifer vadose zone water table zone of aeration (vadose zone) zone of saturation (phreatic zone) 71