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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />, <br />I <br />r <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />movement of water from stream and alluvial material to the aquifer outcrop areas <br />(river conductance) are especially important to the model development. Depending <br />upon which value is used, this model's sensitivity to river conductance significantly <br />impacts the model's computed depletions to the surface drainages. Surface <br />drainages include both the river and the river alluvium. This, in turn, has a direct <br />bearing on the replacement and relinquishment requirements. <br /> <br />The model achieved the best calibration with river conductance at 1 x1 0-4 per day <br />rather than 1x10.s per day as used in previous models. This calibration resulted in a <br />depletion to drainages of 20.7 percent for pumping "not non-tributary" non-designated <br />areas versus 2.9 percent if the smaller river conductance is used (1x10.s per day). <br /> <br />An important issue to understand is that pumping from Denver Basin wells permitted <br />prior to SB-85-5 and wells already permitted pursuant to SB-85-5 will most likely <br />deplete the net discharge from the Denver Basin aquifers. Additional pumping from <br />future wells would just hasten the time when total depletion occurs. <br /> <br />Chaoter 10 - Nontributary Groundwater Use and Long-term Impact on Water <br />Rights <br /> <br />This chapter analyzes the use of non-tributary ground water and its long-term impacts <br />on water rights. For the purposes of this analysis, we addressed impacts that result <br />from either non-tributary or "not non-tributary" pumping of the Denver Basins Aquifers. <br />We also looked at the impacts on surface water rights and tributary ground water <br />rights in the South Platte and Arkansas River drainages as well as the impacts to <br />designated ground water rights, both during Denver Basin Aquifer pumping and after <br />such pumping ceases. <br /> <br />It is difficult to determine whether the current replacement requirements will be <br />sufficient for making up stream depletions associated with new pumping. Any ability <br />to make such a determination will depend upon obtaining accurate groundwater <br />diversion records for both existing and new well owners. The State Engineer <br />currently has limited resources with which to obtain these records. Although well <br />owners are required to maintain ownership and address information in the State <br />Engineer's records, few do. Even when the State Engineer can identify these users, <br />not all measure their diversions or maintain records of past diversions. Without the <br />ability to obtain diversion records by mail or other efficient method, the staff of the <br />State Engineer would have to resort to visiting each well on a regular basis to read <br />meters (assuming they were installed and operating) or to issuing orders to install and <br />provide annual records from totalizing flow meters. The State Engineer would require <br />additional staff to obtain this data. <br /> <br />It may be necessary to conduct additional modeling using better data that may have <br />to be collected through additional fieldwork. In particular, data on the amount of <br />historical pumping may have to be improved through field investigations and user <br /> <br />- 11 - <br />