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I I I I I I I I I I I I I I I I I I I February 2000 CR WCD * Yamp:t Riter Basin Small Reserwir Study * Page . 8 2.2 WATER USE The major conswnptive water use in the basin is agriculture. Municipal and industrial depletions are much smaller, but are very important economically. Recreation is becoming more and more imponant economically and will probably experience significant growth over the long-term. However, recreational water demands are typically not conswnptive. Figure 3, Basin Water Denands, displays the basin irrigated agricultural lands, municipal centers, and major industrial users. The Colorado Division of Water Resources Division 6 (Division 6) water records indicate that existing uses deplete approximately 120,000 ac-ft annually. Irrigation diversions consume the largest amonnt of basin water, acconnting for about 78,000 ac-ft of the annual conswnptive use. Diversions generally occur between May and October, with the peak demand in July. However, irrigation use in some locations may be constrained by supply in late season and in dry years (Ken Holt, personal communication, 1999). BBC (1998) projected that annual depletions may approach 170,000 ac-ft by 2045. However, their study indicates that most new depletions would be associated with municipal and industrial uses. Long-range forecasts suggest that irrigated agricultural uses will remain relatively constant between 1999 and 2045 (BBC, 1998). While the BBC repon suggests that significant increases in irrigated agricultural are not likely, the River District wants to assure that existing and future agricultural water- supply needs can be satisfied. The need to assure an adequate water-supply for existing and future irrigated agricultural needs in the Yampa River basin is the driving force behind this study. Ranching and agriculture are imponant economic activities in the region. Approximately 1.7 million acres of land in Moffat and Routt connties are dedicated to ranching and agricultural uses (BBC, 1998), with the bulk of ranch lands dedicated to grazing pasture. Irrigated lands, primarily for hay production, have averaged aronnd 87,000 acres during the 1990's (Ken Holt, personal communication, 1999). Hay production suppons livestock operations and provides a cash crop for local ranchers. The demand for hay production will remain as long as local ranchers maintain their livestock inventories. The expon of basin hay supplements many local ranchers income (BBC, 1998). Local hay has a reputation as premium horse hay, and there is a strong demand for it on the Front Range and throughout the west. Based on its cultural and economic significance, hay crops will be a pan of the landscape throughout the foreseeable future. 2.3 HYDROLOGY Most of the yield of the Yampa River basin is produced by melting snowpacks in the higher elevations in the eastern pan of the basin. Streamflow is highly seasonal, typically peaking in late spring! early summer and rapidly declining through the summer months to base flow. Approximately 64 percent of the 1.1 maf of annual stream discharge recorded at the Mayben, Colorado gage occurs in May and Jnne. Water yield also varies spatially across the basin, reflecting spatial climatological variation. Annual precipitation ranges from more than 50 inches in the high alpine zones in the east and south to negligible amonnts in the arid western portion of the basin (United States Forest Service [USFS], 1993; Natural Resource Conservation Service [NRCS], 1999). 2.3.1 Basin Streamflow There are 21 operating streamflow gages in the basin (United States Geological Survey [USGS], 1999; Colorado Division of Water Resources [CDWR], 1999). Most of these gages are on the mainstem Yampa River or major tributaries. Approximately 63 other gages have been operated by the USGS in Montganery Watson Minirf: Group . P.O. Box 774018 . SI:etJJT1J:o:zt Springs, 0J0rad0 80477 . (970) 879.6260 W..W1'/OSl~_~(DMft/lpt.12.2M9) 12/21/99 SLW