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earliest measurement in a given season was used in the analysis. The change in spring-to-spring <br />and fall-to-fall water levels were calculated and averaged by well. The results are presented iln <br />Table 5. <br />Table 5: Comparison of Water Level Trends <br />Water Level <br />Change Spring to Spring <br />Measurements Fall to Fall <br />Measurements <br />-6 to -5 0 1 <br />-5 to -4 0 0 <br />-4 to -3 1 0 <br />-3 to -2 3 2 <br />-2 to -1 9 14 <br />-1 to 0 54 52 <br />0 to 1 14 12 <br />1to2 2 2 <br />Total 83 83 <br />Table 5 shows that there is little difference in the year-to-year changes in water levels when <br />using either spring-to-spring or fall-to-fall changes u1 water levels in the alluvial aquifer. Both <br />spring and fall changes also show a slight decline in water levels, indicating a slight overall <br />drop iIn aquifer water levels iln the past decade. Since spring-to-sprung and fall-to-fall water <br />level changes reveal similar annual trends, it appears that water levels collected after the <br />grow>ing season does not reveal long-term water level trends any better than measurements <br />taken before the grow>ing season. The trends shown in Table 5 also suggest that it is not <br />necessary to collect measurements in both sprung and fall for evaluat>nng long-term annual <br />changes in tlne alluvial aquifer. However, collecting spring and fall measurements does reveal <br />tlne seasonal fluctuations in water levels during a year as shown by the data collected from data <br />loggers installed in alluvial wells (Section 2.2.1). Therefore, the value of comparing spring-to- <br />spring and fall-to-fall measurements is not in evaluating long-term trends, but rather in <br />evaluat>nng seasonal aquifer response to wet and dry conditions for rainfall and runoff <br />compared to tlne average hydrologic conditions. For example, in a dry year, fall-to-fall <br />measurements may show a large change iln water levels (compared to tlne average fall-to-fall <br />change) which maybe due to increased reliance on groundwater and reduced recharge from <br />surface water sources in the preceding growing season. <br />3.0 Installation of Data Loggers in Bedrock Wells for Long-Term <br />Monitoring <br />The objective of this sub-task was to recommend a set of bedrock aquifer wells suitable for <br />continuous water level monitoring near major pumping centers, and then instrument those <br />wells with data loggers to obtain a continuous water level record. This expands the monitoring <br />of bedrock water levels beyond well DSSBR01, an Upper Arapahoe well located near Bennett, <br />Colorado. This objective was satisfied in Phase 3, as described in the follow>ing sections. The <br />water level data collection from these wells is discussed in Section 2.2.2. <br />SPDSS Phase 4 Task 39 Technical Memorandum-Final 18 <br />O~i20%2008 <br />