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'Predicting Annual Variation of Salinity Production from the Upper Colorado River Basin Using SPARROW '
Jongho Keum (j.keum@aggiemail.usu.edu), Utah State University Jagath Kaluarachchi (jkalu@engineering.usu.edu), Utah State University

The Colorado River Basin has suffered high salinity from both natural conditions and anthropogenic activities which precipitate dissolving salts. The annual salt load at the Hoover Dam located in the lower part Colorado River recorded 9 million tons, and the economic damage is estimated at 383 million dollars based on 2009 salinity concentrations. In order to manage salinity in the Colorado River Basin, water quality standards given as TDS concentration are established at three monitoring stations. Therefore, efforts have been underway to study salinity generation and transport, and develop salinity mitigation strategies. As a part of these efforts, the SPARROW (SPAtially Referenced Regressions On Watershed attributes) surface water quality model developed by U.S. Geological Survey was applied in an earlier study to the Upper Colorado River Basin to predict salinity production and to estimate how the salinity-related parameters affect in the water year 1991. Since this application about 20 years ago, there is a need to extend this earlier work to evaluate the applicability of SPARROW in modeling salinity in the past two decades. Also hydrologic and climatic conditions together with land cover have changed since 1991. In this work, SPARROW modeling was extended up to 2011 with updated land cover, and hydrologic and climatic data. In addition, the observed salinity loads were updated at each monitoring station for each year as well. The results from this recent modeling effort revealed that the salinity loads generally follow the trend of stream discharge. From the SPARROW model, it is shown that geologic sources and point sources do not have any particular trend in the recent decade; however, irrigated lands that occupy a small percent of the total land area have increasing salinity production trends indicating that agricultural is producing significant amounts of salinity to the lower basin.