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`Global Solution' to Colorado Water Dispute Under Study A new study is under way to evaluate a possible "global solution" to ongoing water disputes between Colorado's rural Western Slope and the more urban Front Range around Denver. The study will examine the feasibility of building an off - stream reservoir near Wolcott, Colo., that could supply water to irrigators who now receive their water from Green Mountain Reservoir. The project also would provide water for environmental uses of the Eagle River, a tributary of the Colorado River, and free up water in Green Mountain Reservoir for use by Front Range cities. Details of the proposal are still sketchy, but parties hope a plan will emerge that harmonizes the interests of Western Slope irrigators with the Front Range's growing water needs while also enhancing habitat for endangered fish. Earlier technical studies concluded that a Wolcott Reservoir could hold between 160,000 and 350,000 acre -feet of water, and a 2004 feasibility study looked at three smaller storage scenarios. Front Range and Western Slope agencies will share the $200,000 cost of Study Finds Salt Cedar Management Options Limited Opportunities for managing salt cedar as a way of augmenting water supplies may be limited, according to a white paper produced by the Arizona Department of Water Resources (ADWR). The study cites the presence of endangered species, complex land ownership and variability in evapotranspiration (ET) rates as factors that should be considered before undertaking a salt cedar removal or eradication project. Salt cedar has become established in several reaches of the Colorado River, mainly south of Davis Dam. Where it is established, salt cedar's deep root systems the new study, which will evaluate cost, water quality and hydrology. In addition to looking at the feasibility of a Wolcott Reservoir, the study will evaluate re- operation of Green Mountain Reservoir, about 60 miles west of Denver, to allow Grand Valley irrigators, who currently receive about 52,000 acre -feet of water from Green Mountain, to draw their water from Wolcott. The switch would allow water to be diverted from Green Mountain to the Front Range via the existing Roberts Tunnel. Water from the proposed Wolcott Reservoir also would be used to enhance fish habitat in the Eagle River. Results Unclear from Glen Canyon Flow Experiments Despite a decade of experiments, scientists are still unsure what effects different flow regimes from Glen Canyon Dam have on areas below the dam. Several different flow combina- tions have been tried, including simu- lated floods, in efforts to understand how conditions can be improved for native species and recreation to more closely resemble the river's natural flow variations. are believed to deplete groundwater supplies and increase soil salinity, making areas crowded with salt cedar inhospitable to less salt- tolerant native plants. Projects to eliminate salt cedar by physical removal have proved costly, and water quality concerns limit eradication projects using chemicals. The ADWR paper notes that studies of salt cedar removal projects have yielded mixed results. A recent study cited in the paper concluded that increases in water yield following salt cedar removal were likely to occur only when a salt cedar stand containing high leaf area was replaced by vegetation with a low leaf area. Other studies indicate In early October, Reclamation continued with a series of short -term flow experiments in an effort to understand the relationship between dam operations and dissolved oxygen concentrations in the river. Low dissolved oxygen levels are harmful to fish. A combination of large amounts of sediment and organic matter from a five -year drought followed by above - average runoff during the spring and summer of 2005 has depleted dissolved oxygen levels below the dam. Researchers are trying to determine if low releases spread among varying numbers of generating units will inject more oxygen into the water. During August and September, Recla- mation tried a series of alternating steady and low fluctuating experimental releases to evaluate their effects on sediment movement and native fish. The experi- ments were recommended by the Glen Canyon Adaptive Management Work Group. Living Rivers, a group that advocates decommissioning Glen Canyon Dam, issued a report in late October conclud- ing that the adaptive management program has done more studying than acting to recover endangered species and rebuild habitat in Grand Canyon. - wide variability in ET measurements for salt cedar, suggesting that water yield improvements also could vary after removal projects. Opportunities for removal projects also are complicated by differing land ownership and management along key reaches of the river, the ADWR study found. Federal and state agencies, Indian tribes and private land owners control access to land where removal projects might occur. In addition, native species, such as the Southwest willow flycatcher (listed as endangered under the federal Endangered Species Act), nest in salt cedar along the west side ofTopock Marsh. - WINTER 2005 -2006 • RIVER REPORT • COLORADO RIVER PROJECT • 3