Water Mass Balance to Assess the Status of the Ogallala Aquifer in the Texas Panhandle

Agricultural production in the Texas Panhandle is highly dependent on the Ogallala Aquifer as the primary reliable source of irrigation water.  It is widely understood that in Texas this is a non-renewable resource because recharge is minimal and not capable of matching irrigation withdrawal rates.  Current estimates of available water are based upon measurements of water levels, primarily in pumped wells, during periods of minimal pumping activity (January and February).  The general trend shows a decrease in water surface elevation in the wells; however some areas seem to not decline and in a few places water levels appear to be increasing.  The strategy for the Ogallala Aquifer in Texas is the 50-50 plan; i.e., 50 percent of the water is to be remaining in the aquifer in 50 years.  Application of a water mass balance provides insight into the mechanics of aquifer behavior and reasonable explanations for observed phenomena.  The mass balance suggests that in areas still under irrigation where well capacities have significantly declined, there is more water in storage than determined by water elevation measurements, but the quantities of water withdrawn are also greater than estimated.  In areas where water levels have not declined as sharply, the methods of estimating reserves yield values comparable to well measurements.  The implications for the 50-50 strategy are significant.