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<br />South Metro Groundwater Model Development Report <br /> <br />Oct. 11. 2001 <br />Page 12 <br /> <br />Rather than describing the results for each and every model run, we have selected a small <br />subset of representative model results that illustrate the strong uniformity of regional <br />drawdown predictions for all aquifer descriptions. <br /> <br />) <br /> <br />4.2.1 Areal Head Distributions <br /> <br />For all simulations, 120 years of pumping stress led to a complete de-watering of the <br />system. This should be no surprise, since we specified the pumping rate to be equal to <br />I % of stored volume per year. We therefore consider only results for 60 years of <br />pumping stress, which still represents a fairly significant dewatering of the system. <br />Recalling that the original pumping rate for cells with wells (108 cells out of the 144 total <br />cells) was specified to correspond to 1% of stored aquifer volume per year, one can <br />surmise that the model domain should be somewhere around 50% de-watered. <br /> <br />The regional head distributions after 60 years of pumping for the single-layer and 15- <br />layer models are illustrated in Figures 4.3 through 4.6. Comparing these charts <br />illustrates an increasingly large deviation between the single-layer and I 5-layer results as <br />the vertical conductance (VCONT) is reduced. The difference between the single-layer <br />and the 15-layer base case (with VCONT equal to values presented by HRS, 1997) <br />exhibit negligible differences, but the end member 15-layer cases, jac9b and jac9hvcO, <br />show significant differences, particularly in the areas with no wells. Also worth noting is <br />the fact that the horizontal head gradients monotonically increase as V cont decreases. <br /> <br />J <br /> <br />4.2.2 Well Hydrographs <br /> <br />As shown in Figure 4.3, two locations in the model domain were selected for tracking <br />head versus time hydrographs, MW-I near the domain's southwest comer and MW-2 <br />near the domain's northeastern comer. Figure 4.7 presents the hydrographs at the MW-I <br />location for the single-layer (jac14) and 15-layer (jac9b. jac9c. and jac9hvcO) models. <br />Figure 4.7a shows the comparison for a well completed over all 15 layers, whereas 4.7b <br />illustrates a comparison between the single-layer model and a monitoring well (MW-3) <br />completed in the same location in the deepest layer only. These results show minor <br /> <br />~ <br /> <br />Hydrosphere Resource ConStlltants <br />1002 WaJnut Suilc: 200, Boulder, CO 80302 <br />PO Bo. 445. Sooorro. NM 87801 <br />