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Figure 4 shows where wells in each of the above categories are located. The water level trends <br />for wells in Categories 1 and 2 are apparently related to the type of irrigation occurring nearby, <br />so the irrigated lands are also shown on Figure 4 and are defined by $Ze type of irrigation, either <br />flood or sprinkler. <br />Wells that follow a Category 1 pattern, a rise of water levels during fl1e growing season, are <br />concentrated in the Greeley area, which generally has a large network of irrigation ditches and <br />surface water use. Areas with Category 1 wells more commonly use flood irrigation, which <br />uzvolves the use of water from the South Platte Piver or other surface water sources and <br />provides a source of recharge during t11e grow>lzg season, leading to a rise >11 groundwater <br />levels during the growing season seen in wells in this category. Flood irrigation stops after the <br />growing season and groundwater levels in this category of wells decline until the next growing <br />season. <br />Figure 5 presents the location of DSS02MLK and an inset of its 1ydrograph, which is a <br />representative hydrograph for a Category 1 water level pattern. The figure shows the well is <br />surrounded by flood-based irrigated parcels, which is consistent wit11 the Category 1 <br />hydrograph pattern. The hydrograph has been annotated to explain likely causes of t11e water <br />level patterns shown for wells ii1 this category. From approximately March to September each <br />year there is a water level rise of approximately eight feet in the well shown >lz this figure. This <br />is most likely the result of deep percolation of excess water applied to nearby irrigated fields <br />and from leakage of local irrigation ditches or streams. As shown on Figure 5, water levels in <br />the June to September 2004 and 2005 periods for this well are punctuated by cycles of <br />fluctuating 1ligher and lower water levels. T11is is probably t11e result of pumping at a nearby <br />well or wells. The absence of these fluctuating water levels in the 2006 growing season period <br />indicates that nearby wells were not pumping during the 2006 growing season. In the <br />fall/w>11ter season of eac11 year there is a decl>11e in water levels, sinular to the rise observed in <br />t11e early part of the year (Figure 5). T11is decline is probably the result of water no longer <br />flowing in the irrigation ditches and/ or percolating beneath irrigated fields after the growing <br />season has ended. <br />Wells in Category 2 show a pattern of declining water levels during the growing season. Wells <br />that follow this pattern are located predominantly from Fort Morgan to Julesburg. There has <br />been a conversion of many irrigated parcels in the Fort Morgan area from flood irrigation to <br />well-based sprinkler irrigation systems. This has changed the source of irrigation water to be <br />the alluvial aquifer, leading to a decline in water levels during the growing-season seen in wells <br />uz this category. <br />Figure 6 presents a representative hydrograph for an alluvial observation well (DSS05WLD) <br />grouped in Category 2. The hydrograph is inset on a map showing the location of DSS05WLD <br />and the irrigated lands. The irrigated lands in fllis area are mostly sprinkler-based, which is <br />consistent wifll a Category 2 water level pattern. This 1ydrograph presents the opposite trend to <br />that shown in Figure 5 for the Category 1 wells. During the growing season of each year there is <br />a water level decline, which is probably due to the cumulative effect of pumping ilz the <br />neighboring area being greater than recharge due to unconsumed irrigation water. In addition, <br />this water level decline is punctuated by cycles of fluctuating higher and lower water levels, <br />SPDSS Phase 4 Task 39 Technical Memorandum-Final 14 <br />O~i20%2008 <br />