Laserfiche WebLink
Cache la Poudre where the water level elevation grids extend above ground surface. In these <br />areas the water level grids were adjusted to be consistent with ground surface. These areas <br />represent approximately two percent of the alluvial grid area. <br />Contours were then smoothed by adding a nugget effect to the linear variogram model. This <br />process smoothes contours in areas where significant variations in water level measurements <br />exist within a small geographical area. <br />Table 2: Water Level Contour Parameters and Number of Water level Measurements for Each <br />Time Period <br /> <br /> <br /> <br />ear <br /> <br /> <br />loe <br /> <br />Nugget <br />Effect <br />Number of <br />Water Level <br />Measurements Number of <br />Excluded <br />Water Level <br />Measurements Number of <br />Streambed <br />Elevation <br />Control Points Number of <br />Water Level <br />Measurements <br />Used to Contour <br />1968 0.2 225 1,343 7 54 1,390 <br />1978 0.45 225 744 3 54 795 <br />1990 1.1 225 327 4 54 377 <br />2001 1.35 225 373 8 54 419 <br />2003 1.5 225 546 10 54 590 <br />2005 0.8 225 264 0 54 318 <br />A 50-foot contour interval was chosen for each of the five sets of maps developed for this TM. <br />This contour interval was appropriate for presentation purposes due to regional scale of the <br />maps. For several of the historic time periods mapped, contours are not shown in the portions <br />of each map where insufficient data exists. In general, contour lines extend out approximately <br />five miles from the nearest data point. Contours were trimmed manually in remaining areas <br />where water level trends were extrapolated without supporting data. The lack of contour lines <br />on many of the maps indicates the lack of water level data available for parts of the alluvial <br />aquifer. <br />1.5 Water Level Trend Analyses <br />Changes in groundwater levels in the alluvial aquifer were evaluated both spatially and <br />temporally. <br />Spatial Anal <br />Historical groundwater elevation data were utilized to evaluate groundwater trends in the <br />South Platte Alluvial Region. First, individual well data sets were analyzed to determine the <br />total number of measurements and the most recent water level measurement. Wells that had at <br />least three spring (February to April) water level measurements in different years with at least <br />one measurement since 2000 were selected to generate groundwater trends. Depending on the <br />well being evaluated, the water level trends extend back in time to the 1930's. <br />For each well, a trend line was fit to the historic water level measurements to determine the <br />average annual change in water level. Each chart was manually inspected to determine <br />whether the trend line appeared appropriate for the data. The inspection evaluated if the trend <br />line was biased by pumping season data, isolated data values, or by historic data over more <br />recent (post-2000) data. Wells with water level data that appeared to be heavily influenced by <br />SPDSS Phase 3 Task 44.3 TM -Final 9 <br />11/29/2006 <br />