WSP09785 - Laserfiche WebLink

Home Browse Search

0808 INTRODUCTION The lower Purgatoire River flows more than 160 mi from Trinidad Dam and Reservoir (Bureau of Reclamation, 1964a), hereafter referred to as Trinidad Dam, to its confluence with the Arkansas River near Las Animas, Colorado (fig. 1). Since completion of the dam during the late 1970's, regulation of streamflow has affected the quantity and timing of water available to downstream water users. Water supplies in the valley are overappropriated (Colorado Department of Natural Resources, 1975) and, at times, shortages of irrigation water occur when the demand by canal systems exceeds available streamflow. During water shortages, irrigation canals near the Trinidad area, which have junior water rights, sometimes cannot divert river water because the irrigation canals farther downstream near the Las Animas area, which have senior water rights, have a priority for available streamflow. Traveltime and gains and losses within a stream are important basic characteristics of stream- flow. A better knowledge of streamflow traveltime and streamflow gains and losses along the lower Purgatoire River would enable more informed management decisions about the availability of water supplies for irrigation use in southeastern Colorado. In 1994-95, the U.S. Geological Survey (USGS), in cooperation with the Purgatoire River Water Conservancy District (PRWCD) and the Arkansas River Compact Administration (ARCA), studied these characteristics of streamflow along the lower Purgatoire River. Purpose and Scope This report presents the results of a study that used historical surface-water records to evaluate the characteristics of streamflow traveltime and to estimate streamflow gains and losses along the Purgatoire River downstream from Trinidad Dam, hereafter referred to as the lower Purgatoire River. Streamflow data for 15 surface-water sites and daily streamflow diversion data for 13 irrigation canals were analyzed between sites Ql and Q4 (fig. I). Based on available streamflow data collected from January 1984 through December 1992, three river reaches were identified inthe lower Purgatoire River for reporting ,the study analyses. Reach 1 began immediately ,(0.1 mi) downstream from Trinidad Dam (site Ql) iand extended 60.6 mi to Purgatoire River near 'Thatcher (site Q2). Reach 2 extended 40.1 mi from ,site Q2 to Purgatoire River at Rock Crossing near Timpas (site Q3). Reach 3 extended 58.5 mi from site Q3 to Purgatoire Rivernear Las Animas (site Q4). In addition, daily mean streamflow and daily stream- flow diversion data from January 1957 through ! December 1967 were used for selected streamflow ,analyses between sites QIA and QIC (fig. 1), and i hourly streamflow data from January 1990 through December 1994 were used to estimate the traveltime 'of selected streamflow peaks between sites Ql and Q4. For this study, streamflow analyses generally were reported for four seasons. Winter was defined as December through February, spring was March through May, summer was June through August, , and fall was September through November. , Acknowledgments Personnel from the Colorado Department of Natural Resources, Division of Water Resources, Office of the State Engineer, provided access to , written diversion records and electronic data bases. Assistance by R. Dennis Petersen and Steven Kastner , in obtaining diversion information for Purgatoire River surface-water sites is gratefully acknowledged. Field tours of irrigated parts of the study area and many helpful discussions were held with personnel from the Office of the State Engineer, Water Division No.2. Water Commissioner Henry (Danny) Marques, representing Water District 19, and Water Commissioner Donald L. Taylor, and Engineering Technician William (Bill) Howland, representing Water District 17, provided invaluable knowledge of past and present (1995) water operations along , the lower Purgatoire River. Description of the Study Area The Purgatoire River originates in the eastern slopes of the Sangre de Cristo Mountains (outside the study area) in south-central Colorado and generally flows northeasterly through parts of three counties [Las Animas, Otero, and Bent (fig. 1)]. ! . I 2 Evaluation of Streamflow Traveltime and Streamtlow Gains an1 Losses along the Lower Purgatoire River, Southeastern Colorado, 1984-92 i .