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The Town of Julesburg, located at the northeastern edge of the study area, provided a water <br />level database. Julesburg has 37 alluvial wells in their monitoring network where water levels <br />are collected monthly. Data consists of 1,601 water level measurements from 1992 to 2004. <br />A significant data set was obtained from the USGS by the DWR that consisted of the USGS <br />general water level database for the entire State of Colorado. The database contains additional <br />wells and water level measurements for both alluvial and bedrock aquifers. Water level data <br />was provided by the DWR for Water Division 1 and was queried for alluvial wells located <br />within the SPDSS study area for the current analysis. This query resulted in 5,246 wells and <br />64,459 water level measurements. <br />A database of water level measurements was obtained from the USGS's National Water Quality <br />Assessment (NAWQA) program. The database contains 24 wells located in the South Platte <br />Alluvium Region. Water levels at the NAWQA sites were recorded in July and August of 1994 <br />and 2002. <br />1.2 Data Analysis and Processing <br />Several processing steps were required to convert the data into a format suitable for uploading <br />into a HydroBase compatible database and for subsequent analysis and mapping. These steps <br />are described below. In some of the discussion, there is reference to specific tables and fields <br />contained in HydroBase; these are described in Section 2 of this TM. <br />Aquifer Assi n <br />All measurements were assigned to an aquifer, using the DWR aquifer definitions summarized <br />in the Introduction section above. No attempt was made to verify the accuracy of aquifer <br />designations for wells as provided by an outside entity. <br />Data obtained from the USGS general database contained a 7-character alphanumeric USGS <br />aquifer code classification, such as '125DNVR'. This USGS aquifer code was correlated to the <br />DWR Denver Basin and alluvial aquifer classifications using an aquifer formation and soil type <br />key provided by the USGS. <br />Selection of Temporal Data <br />Water level data in the South Platte Alluvium Region was analyzed for up to six distinct time <br />periods. The South Platte Alluvium Region water level database was evaluated to identify a <br />series of time periods where a sufficient amount of data was available to allow mapping of the <br />water table surface. This was determined by summing the number of measurements recorded <br />for the alluvial aquifer for each year and for each month over the period represented by the <br />database. Summaries of the results are shown in Figures 2 and 3. <br />Figure 2 shows the number of measurements collected by year. Water level measurements <br />began in 1926 and increased to about 200 per year by the early 1950s. The number of <br />measurements increased to about 2,800 per year by the mid 1970s, and decreased to 950 <br />measurements in 1979. The number of measurements decreased between 1979 and 1984, <br />SPDSS Phase 3 Task 44.3 TM -Final 6 <br />11/29/2006 <br />