SPDSS_Task44-3_LowerSPlatteAlluviumRegionAquiferWaterLevels

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the surrounding aquifer based on the shape of the water table contours, but help constrain water levels in areas where no data are available. In 2001 (Figure 7), the available water level data used for contouring consisted of 419 measurements (Table 2). The data are distributed throughout the region except for the upper reaches of the Cache la Poudre where spring 2001 measurements were not available. In this time period additional water level data was available for Weld County south of Greeley and the Julesburg area. As in previous years, streambed control points were inserted along the mainstem of the South Platte from Ft. Lupton to Julesburg since there is an absence of water level data from Ft. Morgan to Julesburg. In this year, the DWR's South Platte alluvial water level program wells located in this reach were not measured until May and were not used for contouring. Water level elevations show similar contours as those created for preceding years. In 2003, CSU provided water levels from approximately 170 additional wells in the South Platte Alluvium. This data collection effort provided a greater understanding of the alluvial water levels than in 2001, with a total of 590 water level measurements being available (Table 2; Figure 8). Again, streambed control points were inserted along the mainstem of the South Platte since there is an absence of alluvial water level data from Ft. Morgan to Julesburg. Water level data for the alluvium near Ft. Collins was not available in 2003. The data are distributed throughout the region. Water level elevations show similar contours as those created for preceding years. In 2005, the databases from DWR, City of Thornton and Metro Wastewater Reclamation District comprise a majority of the alluvial water levels collected in the South Platte Alluvium Region (Figure 9). As in previous years, streambed control points were inserted along the mainstem of the South Platte from Ft. Lupton to Julesburg since there is an absence of water level data from Ft. Morgan to Julesburg. In this year, the DWR's South Platte alluvial water level program wells provided data that is spatially distributed about the South Platte Alluvial Region, allowing a regional water table to be developed for 2005 (Figure 9). Data was not sufficient for contouring in the upper Cache la Poudre and in Beaver and Badger Creeks in 2005. Water level elevations in the rest of the South Platte Alluvial Region show similar contours as those created for preceding years Upon review of the alluvial water level elevation contours from 1968 to 2005, the regional water table has remained stable in the South Platte alluvium. This stability is likely the result of the aquifer's hydraulic communication with the South Platte River, its tributaries and diversion canals. Local variations from year to year could be a result of lower or higher than normal stream flows or local pumping. The hydraulic connection and relatively limited spatial extent of the alluvial aquifer allows for quick responses to aquifer stresses or recharge. This local sensitivity in alluvial water levels is identified in the following section which looks at historic water level trends in alluvial wells throughout the South Platte Alluvium Region. 3.2 Water Level Trends The methodology described in Section 1.5 was used to analyze and evaluate historic spring season water trends in the South Platte alluvium over the past 20 to 30 years. Where data met specified criteria specified in Section 1.5, the water level trend in a well was calculated. A total of 289 wells had sufficient data to be able to calculate statistically significant trends (Figure 10). SPDSS Phase 3 Task 44.3 TM -Final 13 11/29/2006