Arkansas - CSU Geospatial DSS for Integrated Water Mgmt_ Application

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Water Supply Reserve Account -Grant Application Form Form Revised May 2007 flows available for downstream diversion and instream use, thereby impacting downstream water right holders as well as possibly violating the Arkansas River Compact between Colorado and Kansas. The Office of the Colorado State Engineer has recently begun the process of drafting stipulated rules that could be put into effect retroactive to 1999 that would restrict conversion to more efficient irrigation methods and the lining of canals if the resulting alteration of return flows is in violation of the Arkansas River Compact. Aside from the salinization of the lands and water resources of the Arkansas River Valley due to inefficient irrigation practice, imposition of these rules would have a negative impact on farmers in the Arkansas River Valley, primarily since sprinklers and other efficient irrigation methods can significantly reduce the cost of irrigation. River basin management methods must be found that will allow improved efficiency and its associated benefits while still abiding by the Arkansas River Compact. Compounding these problems is the continuing attempt by cities and industries along Colorado's Front Range to acquire water rights historically used for irrigation primarily in the Lower Arkansas River Valley to meet increasing urban demands. It is estimated that almost 80,000 acres of prime agricultural lands have been permanently dried up by transfer of agricultural water rights to M&I uses, with many of these water transfers removing water out of the Basin to adjacent watersheds. If these trends continue, it is estimated that over a quarter of the irrigated lands in the Basin could be lost by 2030. Although water users in the Upper Arkansas River Basin have not yet directly suffered from permanent dry-up of their irrigated lands, there is a concern that the potentially large transfers out of the Lower Basin could impact the availability of water to Upper Basin users if changes in timing and point of use are not carefully evaluated. Upper Basin users are also interested in conjunctive use schemes for diverting available flows in right for recharge of the alluvial aquifer in support of water augmentation plans to replace river flows depleted by well usage. There is also concern in the Upper Basin over pollution from mining, availability of water supplies for future population growth, and accommodating instream flow uses for fishing and whitewater sports. If agricultural production is to be sustained and the environmental integrity of the watershed protected, well-designed, economical changes in water management must be made throughout the entire Arkansas River Basin, including improving irrigation efficiency, modernizing the water-delivery infrastructure, installing subsurface drainage systems, and adopting more salt-tolerant crop varieties. Preliminary results from field and modeling studies conducted by the project directors indicate that such changes have substantial potential for lowering the saline shallow water table, reducing soil salinity, and increasing crop yields on valley lands. Beyond significant reductions in salt loads to the river would result, along with diminished water losses to nonbeneficial consumptive use. Opportunities exist for application of the Arkansas River GeoDSS proposed herein for managing flows in the River that not only preserve in-state water rights but also must respect the requirements of the Arkansas River Compact between Colorado and Kansas. Basin-scale changes in river operations, both upstream and downstream, can be developed to dampen the effects of actions taken to improve regional conditions on the land. For example, it may be possible to offset the impact of regional improvements on river flows by altering the timing of storage and releases at Pueblo and John Martin Reservoirs, thereby preserving river flows that comply with Colorado water rights and the Arkansas River Compact. If historic flow patterns cannot be fully preserved, benefits from improved river water quality may justify these changes. Moreover, there appears to be promise for significant improvement in Arkansas River water quality at the state line, which will benefit irrigated agriculture in Kansas. 10