GEOS 1004 Lecture Notes - Lecture 26: Water Cycle, Aquifer, Arsenic
8 Mar 2018
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How can large population centers exist in arid regions: use groundwater from aquifers that are recharged from above from far away (i. e. hundreds of miles). E. g. western great plains use groundwater sourced from the rockies. Groundwater flow is slow; it may take thousands of years for water to flow from its source. Water may also be relict (old) from wetter climate (glacial times). If extraction exceeds recharge, groundwater is non-renewable and may only sustain for a limited time. Because of the hydrologic cycle, you"d expect water to be a renewable resource. For groundwater to be renewable, the rate of use or extraction must not exceed the rate of recharge (i. e. balanced budget). Nationally it"s renewable; 25% of available water (i. e. precipitation) is used per year. (water use in us: 6000 liters (1620 ga) per day per person (~1/5 is municipal use)). 2)engineered importation of water from somewhere else via pipelines and aqueducts. Southern california gets its water from the mountains.
