Originally posted by denver22
...underground resources are mainly still untaped
Change in groundwater storage The USGS estimated that total water storage was about 2,925,000,000 acre feet (3,608 km3) in 2005. This is a decline of about 253,000,000 acre feet (312 km3) (or 9%) since substantial ground-water irrigation development began, in the 1950s. Water conservation practices (terracing and crop rotation), more efficient irrigation methods (center pivot and drip), and simply reduced area under irrigation have helped to slow depletion of the aquifer, but levels are generally still dropping. See the figure above for an illustration of the places where large drops in water level have been observed (i.e., the brown areas in southwest Kansas, and in or near the Texas Panhandle). In the more humid areas, such as eastern and central Nebraska and south of Lubbock, water levels have risen since 1980.