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<br />OO~055 <br /> <br />C. Groundwater Impacts <br />~<'. :.. ...~1 '. <br /> <br />Groundwater may be a renewable or a finite resource depending on whether overlying <br />geology allows recharge of the aquifer. <br /> <br />Where aquifers are recharged, tbey usually are hydraulically connected, or tributary, <br />to the surface water system. Colorado water law recognizes this physical connection and <br />tributary groundwater is allocated and administered on the same basis as surface water. <br />These tributary aquifers are recharged by water that infiltrates into the soil and deep <br />percolates down to the aquifers. When the water table rises, groundwater .flows to surface <br />streams that intercept the aquifer. Reduced conveyance losses produce less deep <br />percolation and less recharge. Declining recharge rates reduce tbe rise in the localized <br />groundwater mounds and the regional water table, with potential impacts on well pumping <br />levels and return flows. When well diversions are reduced, pumpers save on energy <br />consumed and agricultural chemicals which motivates them to be more efficient. When <br />tributary w~U pumpers become more efficient they have little absolute impact on the annual <br />water table, because reduced pumping offsets any loss of recharge. When surface irrigators <br />become more efficient they can decrease the supply of water available to wells using the <br />tributary aquifers. <br /> <br />Non-tributary aquifers are geologically isolated from significant surface recharge. The <br />incentive to improve the efficiency of uses of non-tributary aquifers, such as the Ogallala, <br />is to conserve a vanishing resource. Significant efforts are now under way to reduce well <br />pumping by using water more efficiently and tbereby extend tbe life of this finite supply. <br />The allocation and conservation of non-tributary groundwater is beyond the scope of this <br />analysis, but may merit further attention and consideration if the General Assembly is going <br />to create incentives to encourage improved irrigation efficiency. <br /> <br />D. Environmental Impacts <br /> <br />28 <br />