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Long Hollow Reservoir <br />Feasibility Study <br />2.0 PROJECT DESCRIPTION AND PURPOSE <br />2.1 Project Location and Description <br />The proposed LHR will be located in southwest La Plata County, approximately 22 miles <br />southwest of Durango, Colorado in Sections 29, 32, and 33, Township 33 North, Range 12 West, <br />New Mexico Principal Meridian (Exhibit 2.1-1). LHR will be an on-channel reservoir. The dam <br />embankment will be located on Long Hollow approximately 0.5 mile upstream of the confluence <br />of Long Hollow and the La Plata River and 5 miles upstream of the Colorado/New Mexico <br />border. <br />LHR will capture flows from the 43 square miles of the elongated Long Hollow watershed, <br />including groundwater inflows resulting from irrigation return flows and surface water inflows <br />derived from precipitation within the watershed (Exhibit 2.1-2). The current land use within the <br />watershed is predominantly agriculture, with much of the land irrigated when a water supply is <br />available. The northeast-southwest trending mesa that comprises most of the watershed slopes at <br />a uniform grade of approximately 2 percent to the southwest from elevation 8,100 feet to <br />elevation 6,200 feet near the proposed LHR embankment. The Long Hollow channel and its <br />tributaries are incised into the mesa. The average annual precipitation measured at the Fort <br />Lewis station, about 14 miles north of the LHR site, was 18.17 inches for the 32 years of <br />measured record between water year (WY) 1949 through WY 1998. <br />LHR will have an estimated m~imum reservoir pool volume of 5,400 AF. The m~imum <br />operating pool elevation will be 6,312 feet. The average LHR fill volume for the period WY <br />1989 through 2002 (projected by using the water allocation model described in the Long Hollow <br />Phase l Summary Report, WWE 2004, b) will be 3,540 AF per year. Average LHR project <br />depletions, as determined by the United States Bureau of Reclamation (USBR) San Juan River <br />model, will be 1,470 AF per year. Depletions are expected to range from approximately 100 AF <br />to 3,600 AF per year. <br />991-077.120 Wright Water Engineers, Inc. Page 7 <br />April 2005 <br />