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In general, the water levels in the Dawson, Denver, Arapahoe, and Laramie-Fox Hills Aquifers <br />all appear to show local declines over time based on the contour maps of the years plotted, and <br />overall regional gradients similar from one period to the next based on the data available. <br />3.2 Water Level Trends <br />The water level data described in Section 1.5 were used to depict regional water level trends in <br />each of the bedrock aquifers over the past 30 to 50 years. The average annual change in water <br />level elevation in a well was calculated and posted by aquifer for locations where data was <br />available and this data was contoured (Figures 23 to 26). It should be noted that the water level <br />trends depicted graphically in Figures 23 to 26 represent a generalized and regional <br />characterization over a period spanning from the late 1940's/early 1950's to recent times, in <br />contrast to the water level elevation of distinct time periods as shown in Figures 5 to 22. Trends <br />in individual wells were based on linear regression analysis that included engineering <br />judgment. These values were then used to estimate smoothed trends throughout a given <br />aquifer. As a result of the averaging and smoothing procedures used, there is likely to be local <br />variation from the water level trends shown in these figures. However, the trends shown do <br />represent the large-scale annual changes seen in water levels each of the Denver Basin bedrock <br />aquifers on amulti-decade time scale over the past half-century. The data in several of the <br />Denver Basin aquifers show there are stresses (likely caused by pumping) that have resulted in <br />a local decline in the water levels. <br />Water levels in the Dawson Aquifer have generally shown little change in wells in the northern <br />Arapahoe County area and southwest portions of the aquifer in El Paso County (Figure 23). <br />However, the Dawson Aquifer water levels in the vicinity of the Castle Rock in east-central <br />Douglas County have declined at an average rate of between 3 and 5 feet per year according to <br />historic water levels in individual wells. <br />Denver Aquifer water levels have declined at an average rate of 20 to 25 feet per year in wells <br />located east of Castle Rock, in Township 8S, Range 67W, and at an average rate of 15 to 20 feet <br />per year in wells located northwest of Parker, in Township 6S, Range 66W (Figure 24). These <br />localized areas of large drawdown are located near municipal wellfields. Historic water levels <br />in a well located in Township 7S, Range 65W exhibit a smaller decline than in surrounding <br />wells (-4 feet per year), and could be a result of the well not being used for production or from <br />less pumping occurring in the Denver aquifer in this area. Wells located along the northern, <br />eastern, and southern edges of the Denver Aquifer have experienced changes (both rise and fall) <br />in water levels of +/- 5 feet per year, with no regional trends apparent. Water level rises could <br />be the result of recharge, groundwater inflow from the Laramie-Fox Hills aquifer, and/or from <br />a reduction in pumping and the associated recovery of water levels in these areas. <br />Like the Denver Aquifer, water levels in the Arapahoe Aquifer wells also show a large contrast <br />in trends, with rates highly dependent on specific well location. Along the northern, eastern and <br />southern margins of the Arapahoe Aquifer, water levels have declined at an average rate of <br />5 feet per year. Along the western side of the aquifer in Ranges 66W, 67W and 68W, water levels <br />have declined in most locations, with many individual well declines of up to 50 feet (Figure 25). <br />Average annual declines over 150 feet have been observed in two locations: east of Castle Rock, <br />and northwestern Arapahoe County (Figure 25). In north-central Douglas and southwest <br />SPDSS Phase 3 Task 44.2 TM -Final 14 <br />11/28/2006 <br />