Ch11 - Water Resources

Answers to Review Questions and Critical Thinking Questions

Review Questions

1. A watershed or drainage basin is the geographic area that contributes water to a particular stream.
2. The water table separates the unsaturated vadose zone, which lies near the Earth’s surface, and the zone of saturation, where true groundwater flow occurs.
3. An aquifer is a unit of Earth material capable of supplying groundwater at a useful rate.
4. The major factors controlling the movement of groundwater are hydraulic gradient and hydraulic conductivity.
5. Darcy’s Law describes groundwater movement as a function of hydraulic gradient and hydraulic conductivity.
6. Interactions between surface water and groundwater include the exchange of water between rivers and aquifers, and the propensity for pollution of karst groundwater systems by polluted surface water systems.
7. Instream water uses do not withdraw water from its source, while offstream uses remove or divert the water from its source.
8. Consumptive use does not return water to its source, but instead consumes it in some way.
9. The biggest users of fresh water are agriculture and the thermoelectric industry.
10. Water can be conserved by making irrigation more efficient, by using more efficient domestic fixtures and appliances, and by watering lawns and gardens more efficiently.
11. Luna Leopold’s philosophy of water management is centered on the belief that management cannot be successful as long as it is perceived primarily from an economic or political standpoint. His strategy focuses on the principle that water supplies and processes are subject to natural variations, which must be planned for.
12. Wetlands are areas that are either inundated by water or the land is saturated for at least a few days in most years.
13. Important environmental features of wetlands include buffering from coastal storms, filtering of sediment and toxins from water, storage of water during floods, production of nutrients and chemicals, and recharge of groundwater.

Critical Thinking Questions
1. A wetlands inventory would require a knowledge of the types of wetlands present in the student’s region, as well as sources of information, such as public records or time sequences of aerial photographs, on wetland conversion. Finally, the plan must describe some means of addressing the economic and political issues associated with wetlands preservation.
2. The background information for this task is summarized in the Case History on the Edwards Aquifer in this chapter. A response to this task should address the conflicts between municipal water use and environmental protection (including endangered species issues), the high cost and limited availability of alternative water sources, the benefit of clean water to growing economies in the region, the health of aquatic ecosystems, and the threat to water quality at recharge areas.
3. A response to this question will reflect the student’s opinion, but should focus on the link between food production and water use, as well as the shortages that already occur and their linkages to food production.