Answer to Question 1
The High Plains are a relatively dry region extending from South Dakota to western Texas. The natural recharge of the aquifer is very slow, and the problem of declining groundwater levels is acute, as this aquifer accounts for about 30 percent of all groundwater withdrawn for irrigation in the country. In years of average or below-average precipitation, recharge is negligible in the aquifer. Therefore, where intense irrigation has been practiced for an extended period, depletion of groundwater can be severe. The USGS estimates that during the past 60 years, water in storage in the High Plains aquifer declined by about 200 million acre feet (65 trillion gallons), with 62 percent of the total decline occurring in western Texas.
Answer to Question 2
These springs are the result of a perched aquifer. A perched aquifer is a zone of porous and saturated material on top of an impermeable layer, well above the water table. The tendency to flow toward low-pressure areas causes the water to flow out as a spring because it is perched so much higher than the water table.
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Mercury’s Craters and Plains
Groundwater
Problem
Physics - Problem Exercise