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<br />. <br /> <br />. <br /> <br />better resolution in the southem part of the basin, particularly near Colorado Springs. <br />Various pumping simulations were performed using diHerent water demand scenarios <br />and wellfield locations of interest in the Colorado Springs area. We have based a <br />portion of our work on Banta's for several reasons: it is more recent than Robson's <br />work, the smaller cell size provides better resolution, model resulls are available on <br />disk, model code is available on disk for review, an extensive report describing the <br />development and use of the model has been published, and the model has been <br />reviewed by the USGS. <br /> <br />Banta's SIMGRO simulation was used as the basis for this project. The SIMGRO <br />pumping pattems match those of Robson's work in the northem part of the basin and <br />are based on water use projections for the Colorado Springs area in the southem part <br />of the basin. Total pumping for each aquifer in the SIMGRO simulation is presented in <br />Table 3.1 and graphically in Figure 3.1. The first row in the table labeled steady state <br />WITh ending year 1985 since the steady state simulation defines the initial conditions for <br />the SIMGRO simulation which starts in 1985. We see a total withdrawal from the basin <br />in 1995 of 76.1 cfs. Interpolation between 1995 and 2005 gives an estimated 1996 <br />value of 78.8 cts. This compares well with the Senate Bill 74 1996 estimate of total <br />withdrawal from the Denver basin aquifers of 80.8 cts. The data currently available <br />indicate that the SIMGRO simulation matches observed growth. <br /> <br />Mr. Robson and Mr. Banta have both been very helpful in this project and their <br />assistance is greatly appreciated. <br /> <br />4.0 Limitations of Previous Work <br /> <br />In both Robson's and Banta's work, the aquifers are treated as uniform in the <br />vertical section, In actuality, they are known to be made up of inter bedded sandstone <br />and shale layers. Typically, wells are screened only at the sandstone layers and no <br />screen is installed adjacent to the shale layers. Wells completed in this way are called <br />. multi-completion wells. All layers contribute to the well and each layer may have a <br /> <br />8 <br />