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<br />Development of Estimated Daily Flows - Yampa River at Maybell <br /> <br />Daily Power Generation Depletions <br /> <br />Historical depletions associated with the Hayden and Craig Generating Stations were <br />determined from daily records of actual diversions over the study period. These records were <br />supplied by the Office of the State Engineer. Division of Water Resources. All diversions by <br />the Hayden and Craig Stations were assumed to be 100 percent consumptive with respect to the <br />flow measurement gage on the Yampa River at Maybell. The effects of these diversions were <br />then routed to the Maybell gage using the travel times discussed below. <br /> <br />Daily Irrigation Depletions <br /> <br />Irrigation results in the most significant depletions that are imbedded in the historical <br />gaged flow at Maybell. Accordingly, this "correction" to the gaged Maybell flow was given <br />the greatest attention. Historical irrigation depletions were, in general, estimated from potential <br />crop consumptive use adjusted 'for the effects of water supply shortages, groundwater return <br />flows, and river travel times. The agricultural depletion analysis was conducted on a monthly <br />basis. Estimated depletions were then converted to daily values using a spline interpolation <br />scheme. <br /> <br />Historically Irrigated Lands <br /> <br />Estimates of historically irrigated lands are available since the mid-1970's from the <br />Division 6 office of the State Engineer. Since this time, irrigated lands have average roughly <br />70,000 acres in the Yampa River Basin in Water Districts 44, 57 and 58, and acreage has <br />shown little variability from year to year. The Division 6 Engineer has suggested that this <br />same approximate level of irrigated lands likely occurred over the period 1950 through 1982. <br />Information provided on irrigated acreage from the U.S. Department of Agriculture and the <br />U.S. Bureau of Reclamation also showed no time trends in the amount of irrigated lands since <br />the 1930's.. <br /> <br />To estimate historical agricultural depletions over the study period, records of irrigated <br />lands were examined from a 1994 tabulation developed by the Division 6 Engineer. This <br />information was provided in electronic DBase format which listed each irrigation ditch and the <br />number of acres it supplied. This information was then sorted by general geographic location <br />and filtered to exclude any acreage below the Maybell gage (a portion of District 44 extends to <br />the west of Maybell). This process resulted in an estimated 68,700 acres of irrigated lands <br />upstream of the gage. The area of irrigated lands was assumed constant over the study period. <br /> <br />Potential Consumptive Use <br /> <br />Monthly potential crop consumptive use rates were estimated, using the Blaney-Criddle <br />method and historical precipitation and temperature data, for the irrigated crop types <br />determined to be relevant over the study period (primarily pasture hay and alfalfa). Potential <br />consumptive use (PCU) was estimated for each crop type at each of four climate stations in the <br />basin which were in operation during the study period (Yampa, Steamboat Springs, Hayden, <br />and Craig). PCV rates (feet) were developed for each month of the study period. <br /> <br />4 <br />