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<br />So~& Grolmdwa/er Model Developmetll Report <br /> <br />Oct. 11. 2U01 <br />Page 16 <br /> <br />" <br />I <br /> <br />5,0 <br /> <br />PRELIMINARY REVIEW OF 8B-74 GROUNDWATER MODEL <br /> <br />In this section, we examine gross features of the S8-74 model and screen newly acquired <br />data with respect to parameterizations in the SB-74 model. <br /> <br />5.1 88-74 Model Review <br /> <br />To evaluate the S8-74 SEO Denver Basin Groundwater Model as a tool for the South <br />Metro Water Supply Study, we have examined several aspects in detail. Model features <br />examined and discussed here include: <br /> <br />· A comparison of river nodes in the model to maps of alluvial aquifer extent. <br /> <br />. Plots of aquifer top and bottom elevations and hydraulic conductivity have been <br />created for comparison to current and historic data from the Colorado SEO and water <br />suppliers. <br /> <br />. An examination of the pumping scenarios and resulting dry cells. The model cases we <br />have looked at thus far are the C6 (historic pumping), PO (future pumping at ] 996 <br />constant rate), and P3 (future pumping at BASE projection) cases. <br /> <br />) To compare river nodes in the SEO model to alluvia] aquifer extent, overlays were made <br />of the river node distribution in each of the six model layers. These overlays were then <br />matched to a map showing areal extent of alluvial aquifers in the Denver Basin (Figure <br />5.1) (adapted from Fig. 1 of Robson, ] 989). Figure 5.2 shows the river nodes in model <br />layers 5 and 6. A comparison of the river nodes in this figure with the alluvial aquifer <br />extent shown in Figure 5.1 results in a large area of layer 6 that should have additional <br />river nodes. There are also some anomalous river nodes in the other layers that should be <br />removed to make the model more accurate. <br /> <br />A detailed cross-check between the Denver Basin hydrogeologic data reports (e.g., <br />Romero and Hampton, 1972; Robson and Romero, 198], Robson, 1983; Robson, 1987; <br />Robson, 1989) and SB-74 model parameterizations revealed the expected close <br />correspondence. In some cases minor differences were found, although such minor <br />discrepancies likely are due to interpolation, block averaging, and/or parameter <br />adjustment during model calibration and so are oflittle concern at this time. As described <br />. <br />below, a more important and detailed cross-checking involved comparing SB-74 <br />parameter values to hydrogeologic data newly acquired from South Metro water <br />\ providers. <br />) <br /> <br />Hydrosphere Rcsourte Consultants <br />1002 Wainut Suite 200, Bouldor, CO 80302 <br />PO Box 445. Socorro, NM 87801 <br />