Characterization of trends in reservoir storage, streamflow, and precipitation in the Canadian River watershed in New Mexico and Texas

Dams and reservoirs were created on the Canadian River in New Mexico and Texas between 1918 and 1984 to supply water for irrigation and industrial and municipal uses; however, there are indications that the storage in the 4 major reservoirs is insufficient for current demand. This study was conducted to document changes in reservoir storage and streamflow throughout the watershed and to investigate the hypothesis that decreases in reservoir storage since 1990 were associated with changes in rainfall. Time-series analyses indicated that the reservoir storage values for all 4 major impoundments (Eagle Nest Lake, Conchas Lake, Ute Lake, and Lake Meredith) on the Canadian River in New Mexico and Texas during the decade of 2000-2009 were less than the historical means. Streamflows at all 4 USGS gauges on the Canadian River in New Mexico and Texas from 2000 to 2009 were less than the long-term mean flows. Mean annual precipitation from 36 weather stations either in or adjoining the watershed tended to be lower from 2001 to 2010 than the period from 1971 to 2000. The frequency of rainfall events in excess of 50 mm from a weighing rain gauge at Bushland, Texas, from 2000 to 2009 was different from that reported from 1960 to 1979. ArcSWAT, a hydrological model, was able to simulate the observed declines in storage in Lake Meredith from 1990 to 2009 using historical rainfall data. These results support the hypothesis that the decreases in storage in Lake Meredith were associated with changes in rainfall.