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<br />.. c..' -~ ~ I <br />'DddJd <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />49 years for which records are available. The dry year flow in 1977 during the <br />study period was only slightly more severe than a critical drouth in the mid <br />1930's. <br /> <br />Long-term precipitation variation at Mesa Verde National Park has been <br /> <br />studied on the basis of tree-ring chronologies for the period of 740 A.D. to the <br /> <br /> <br />present. The period of 1905 through 1929 was considered to be unusally moist, <br /> <br /> <br />with normal to somewhat dry conditions occurring thereafter. The 1951 through <br /> <br /> <br />1980 study period fell in a generally intermediate precipitation range based <br /> <br /> <br />on the tree-ring studies and was neither unusually moist nor unusually dry. <br /> <br />Diversions in Mancos Valley Area <br /> <br /> <br />Diversion records were obtained from Water Commissioner field books <br /> <br /> <br />available from the Colorado Office of the State Engineer. For the period through <br /> <br /> <br />1974, the Wheeler staff added up the daily diversions for each ditch and prepared <br /> <br /> <br />a monthly diversion summary. For records beginning in 1975, the State Engineer's <br /> <br /> <br />staff has prepared a computer data file of all diversion records in the Mancos <br /> <br /> <br />River basin. Monthly diversion summaries from the computer file were added <br /> <br /> <br />to the manually prepared summaries, to provide complete diversion record sum- <br /> <br /> <br />maries for the 1951 through 1980 study period. Additional diversion records <br /> <br /> <br />for the period of 1938 through 1950 were summarized for ditches located along <br /> <br /> <br />the West, Middle, and East Mancos River and along the La Plata River upstream <br /> <br /> <br />of the Hesperus gage for purposes of streamflow con-elation studies. The Water <br /> <br /> <br />Commissioner summaries of the ditch diversion records are presented in Appendix <br /> <br /> <br />B of this report. <br /> <br />The Jackson Gulch Reservoir Project was completed by the Bureau of <br />Reclamation in 1949. Water is diverted from the West Mancos River into the <br />reservoir and is stored for use as a supplemental irrigation supply in the Mancos <br />Valley. Most of the major irrigation ditches in the Mancos area participate <br />in the project. The reservoir has a 10,000 acre-foot storage capacity. A summary <br />of diversions from the West Mancos River to storage in Jackson Gulch Reservoir <br />is included in Appendix B. <br /> <br />-11- <br /> <br />,:;L <br />