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1483 Jilt J1UG1C1983 ~~ WATER'RESEARCH NEWS co~g~~~~~~;YATCR Colorado Waler Congress. 1390 Logan SI,. Rm, 312. Denver, Colorado 80203 .'P~Q303) 837-0812 Research News Editor, Bill Raley August 19, 1983 STUDY INDICATES THAT THERE MAY BE A GROWING SALINITY - PRDBLEM" ON THEsou'TFi PLATTE -- Dr. Dave Henricks, Professor of Civil Engineering at Colorado State University, directed the study team, funded by an OWP grant through the Colorado Water Resources Research Institute. Monthly salinity and flow recoros were analyzed for the 12-year period 1966-79 for the 213-mile stretch of the river on the lower South Platte between Henderson and Julesburg. About 50 canals divert water to serve approximatelY ? 500,000 acres of land adjacent to the river. Municipalities and industries divert only about 7 percent of the water The study showed that river salinity increased from 75 milligrams per liter average at the headwater to 1600 milligrams per liter at the Nebraska border. The salt concentration in the river increased sharply from Henderson to Kersey; however, there .1s a decrease in salinity between Balzac and the state 11ne. This would indicate that salt is being leached and transported from the upper irrigated land and deposited on the lower irrigated land between Kersey and Bslzac. There must be a salt balance (amount of salt deposited equal to amount of salt leached) for the irrigated lands between Kersey and Balzac or the aocumulation of salt on the land will reduce crop production. Most of the salt comes from saline return flows which reach the river and are diverted for direct reuse during the summer, but are held in storage during the fall and winter seasons. If the fall and winter saline water diversions could be replaced with higher quality water from upstream storage, such as the proposed Narrows or Hardin reservoirs, the rate of salt accumulation on the land could be reduced_ One alternative would be to construct a by-pass canal around the proposed reservoirs to carry salt-laden water from upper lands. This water would be allowed to flow out of the state during the fall and winter. Other alternatives include improved drainage on the lower lands and more ~fficient irrigation practices on the upper lands to reduce return flows. Por more information, contact: Dr. David Hendricks, Department of Civil En- gineering, Engineering Research Center, Coiorado State University, Fort Collins, Colorado 80523 (phone 491-8273). LEGISLATURE FUNDS EXPANSION OF SOUTH PLATTE MODEL The' 1983 General Assembly earmarked $130,000 of Colorado Water Conservation Board funds for expanding the South Platte Conjunctive Use (ground and surface water) Computer Simulation Model. The model ie presently 'operational on the lower 100 miles of the South Platte between Balzac and Julesburg. During the next two years, d~a will be entered'for the upper part of the river between Balzac and Denver. Stream inflow data from the tributaries including the Cache La Poudre, Big Thompson, 'St. Vrain and Clear Creek will also be added. When the model is completed from Denver to Julesbtirg, it will provide the first opportunity to look at a major portion of the river's hydrology and water right system as one unit. ' The model can be used to study effects of proposed reservoirs on the entIreJr1ver stystem and to help develop voluntary exchanges and augmentation plans. A major use of the model could be to study ways of using groundwater more efficiently, thus reducing flows out of