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07/03/2084 12:81 3/1J2!J'::ICll!JCI W~lGHI WAlt~ tNG lNG t-'AGt:. t1L 001793 La Plata River Consumptive Use Study November, 2000 Executive Summary On July 11,2000 the Colorado State Engineer imposed the futile call doctrine on the La Plata River. This action relieved Colorado water officials from the obligation to deliver one-half of the measured streamflow at the Hesperus, Colorado river gaging station to the stateline, thereby allowing Colorado water users to capture and utilize these marginal flows. The futile call decision was based upon a number oftime/site specific physical and climatological conditions and in perspective of historic practice that dictated the low flows would seep into the dry river channel and not reach the stateline. Based solely upon the parameter of consumptive use by native vegetation along the La Plata River channel, the Colorado State Engineer was justified in his decision to declare any attempt to deliver the low streamflows in late July and August of 2000 to the stateline as futile. During August 2000 the daily average flow of the La Plata River at Hesperus was 10.9 cfs. In the same time frame, the consumptive use of riparian native vegetation from the Hesperus Gage downstream 5.2 river miles to the Hay Gulch Ditch would consume an average of 11.0 cfs, if water were available. Results of a Blaney-Criddle analysis indicate the native vegetation along the La Plata River corrid~x:!!:om Hesperus to the Colorado/New Mexico stateline consumes an average daily flow ~uring August. Purpose of Study The primary intent for creation of the La Plata River Compact' distribution of water and to remove present and future controve \'Iexico. During the summer of 2000, the La Plata River experienced se" Colorado water officials scrutinized the rapidly declining natural streamfl .tpanion to existing hydrological, climatological, and physical characteristi(uio State Engineer detennined that attempted delivery of water from the u . or one- half of the measured streamflow at Hesperus, to the stateline COli _ _~._.u.";ull use in New Mexico and therefore any attempts to do so would be futile. l'lew Mexico water officials question the validity of this determination. The purpose of this study is to analyze the potential consumptive use of water by natural vegetation or phreatophytes along the La Plata River. Between Hesperus, Colorado and Farmington, New Mexico approximately 3,580 acres of riparian 1 wetland plant communities were identified within a I-mile corridor along the La Plata River!.. Of this amount, approximately 2,350 acres were identified by the Bureau of Reclamation to be within the river's zone of influence. The section of the La Plata River under investigation in this report is the 25.4 river-mile section between the Hay Gulch Ditch (0.5 miles below the Hesperus Gage) and the confluence of Long Hollow and the La Plata River. For purposes of this study, the river was segmented into six defined reaches as: Reach 1 - from the confluence with Long Hollow upstream to Cherry Creek Reach 2 - from the confluence with Cherry Creek to the Joseph Freed Ditch Reach 3 - from Joseph Freed to the intersection ofCmmty Rd. 141 & Hwy. 140 Reach 4 - from GR. 141 & Highway 140 upstream to the H+H Ditch wasteway Reach 5 - from the H+H Ditch wasteway to the Big Stick Ditch Reach 6 - from the Big Stick Ditch to the Hay Gulch Ditch headgate Width of the La Plata River canyon varies in this reach from 300 to 1500 feet with an average width of 500 feet. The definitive river channel fluctuates between 15 and 30 feet in breadth. The prevalent soil