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<br />. .E. APPROACH: <br /> <br />Currently (1998), during March and October of each year, the U,S. Geological Survey measures ground-water <br />levels in 6 wells in the study area, Because these data are insufficient to map the areal extent of the high water <br />table in the study area, water levels will be measured in about 50 wells that are completed in the alluvial <br />aquifer in the study area during February or March of 1999, A map of the depth to water and a map of the <br />water-table surface will be prepared from these point data. The water-table map will include contours showing <br />the elevation of ground water and will be useful for comparing ground-water levels to local features such as the <br />Arkansas River. The depth to water map will include contours showing the depth to ground water and will be <br />useful for indicating where the water table is close to the land surface, <br /> <br />Temporal trends will be evaluated for ground-water-level data from the U.S. Geological Survey's Ground- <br />Water Site Inventory (GWSI) data base and, if available, historical water-level data collected by other entities. <br />If additional water-level data are not available, the analysis will be limited to evaluating water-level data <br />collected after 1965, The principal methods to evaluate trends will involve simple time series plots; however, if <br />trends appear they will be quantified numerically, Any detected trends in ground-water levels will be compared <br />with discharge in the Arkansas River and major tributaries, diversions to the Fort Lyon Canal, the amounts of <br />winter and project water in the Fort Lyon Canal, and ground-water withdrawals used for irrigation to determine <br />if these phenomena are correlated. <br /> <br />. <br /> <br />Aggradation, or increases in the base level of the channel of the Arkansas River bed at the local (Arkansas <br />River at La Junta) and other gaging stations (Arkansas River at Catlin Dam and at Las Animas), will be <br />evaluated by preparing a time series of river gage heights for specific rates offIow, a technique often referred to <br />as specific stage (Simon, 1994). The analysis will require information concerning stage-discharge ratings and <br />the applications of shifts to those ratings for the gaging stations involved. The analysis is designed to show, for <br />example, if river stage integrated across the channel, has increased for a given discharge through time. <br />Although the results of such an analysis will be site specific and not describe conditions for a reach of the <br />channel they are expected to be useful for indicating local conditions. In addition, the specific stage analysis <br />will be supplemented with additional information that may be available such as monumented cross sections <br />and aerial photography. <br /> <br />F. BENEFITS: <br /> <br />The study will bring existing information concerning ground-water levels in the study area up to date and <br />define the current (1999) extent of high water table conditiQns, In addition the study will depne relationships <br />between changes in ground-water levels_and_hydrologic conditionlluch as_di~char~e in the Arkansas River- <br />a~d majo~ tributaries, and the Fort Lyon Canal, i~;;-~4:;~ter_ withdrawlil~.':!s~d for irrigliEon,and potential. <br />aggradation in the Arkansas River. The findings of the study will provide managers with reliable and impartial <br />information for their use in reducing property losses associated with damage to homes and cropland in the <br />study area, <br /> <br />G. REPORT: <br /> <br />The results of the study will be published as a Water-Resources Investigations Report by the U.S. Geological <br />Survey, A draft of the final report will be submitted for cooperator review by the end of May 1999. Oral <br />progress reports will be provided as requested. <br /> <br />. <br /> <br />2 <br />