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<br />. <br /> <br />. <br /> <br />I <br /> <br />was established between recharge to and discharge from each aquifer. In <br /> <br /> <br />the equilibrium situation the average annual discharge from each aquifer <br /> <br /> <br />equaled the average annual recharge from precipitation. Natural discharge <br /> <br /> <br />included not only the underflow at the confluence with the South Platte, <br /> <br /> <br />but also discharge by means of evaporation and transpiration in those areas <br /> <br /> <br />where the water table was near or at the land surface. <br /> <br />I <br /> <br />I <br />I. <br /> <br />,I <br />I <br />II <br />I <br />! <br />, <br /> <br />Man's activities, such as pumping and use of the ground water, importa- <br /> <br /> <br />tion of surface water, and/or modification of the natural recharge processes <br /> <br /> <br />change the recharge-discharge balance. If development of the ground water <br /> <br /> <br />in such an aquifer is too great, an imbalance of discharge exceeding the <br /> <br /> <br />recharge occurs, resulting in depletion of the water in storage. Such an <br /> <br /> <br />imbalance has occurred in the alluvium of the Bijou and Kiowa Creeks, aqui- <br /> <br /> <br />fers which are similar to those under study here. Situations of this type <br /> <br /> <br />are often referred to as ground-water mining operations. <br /> <br />I <br /> <br />On the other hand, there is a level of development of each aquifer <br />which will result in a new equi.librium. This "safe yield" development will <br />result in a lowering of the water table, thus reducing the natural discharge <br />by underflow and evapotranspiration. The ground-water storage volume is <br />then utilized as an operational reservoir; i.e., drawn upon during years <br />of below.normal recharge and replenished during years of above-normal pre- <br />cipita tion. <br /> <br />I <br />II <br /> <br />I <br /> <br />I <br /> <br />If, in addition, the recharge can be increased by inducing more of the <br /> <br /> <br />natural precipitation into the ground-water system or by importing new <br /> <br /> <br />water into the basin, the "safe yield" can be increased accordingly. <br /> <br />I <br /> <br />In the analyses which follow, the safe yield of each aquifer is esti- <br /> <br /> <br />mated. These estimates are purposefully conservative because sufficient <br /> <br /> <br />information is not available to make precise evaluations. However, as <br /> <br /> <br />development and use progresses, further information on characteristics of <br /> <br /> <br />the aquifer will contribute to refinements of the safe-yield estimates. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />II <br /> <br />- 3 - <br /> <br />M. W. BITTINGER AND ASSOCIATES, INC. <br />