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<br />" <br /> <br />rv <br />l'') <br />W <br />OJ <br /> <br />I. INTRODUCTION <br /> <br />A. Overview <br /> <br />This Annual Report presents a summary of the <br />1995 Monitoring and Evaluation (M&E) <br />activities within the McElmo Creek Unit of the <br />Colorado River Salinity Control Program. M&E <br />activities are conducted in accordance with two <br />guiding documents: the "Framework Plan for <br />Monitoring and Evaluation in the Colorado River <br />Salinity Control Program" dated June 23,1991, <br />and the more specific "Monitoring and <br />Evaluation plan for the McElmo Creek Unit of <br />the Colorado River Basin Salinity Control <br />Program" revised April 1994. (The latter <br />document is the proper reference for a more <br />detailed description of the McElmo Unit M&E <br />program scope and methodology.) <br /> <br />M&E activities were initiated in the McElmo Unit <br />in 1990. Field data collection began in 199 I. <br />Reliable irrigation data was not collected until <br />1995 because of the loss of key personnel <br />involved in the M&E activates. Wildlife Habitat <br />ass.essments and Economic eva\uat\ons were <br />carried out as planned. <br /> <br />8, Project Setting <br /> <br />The McElmo Creek Unit, known locally as the <br />Montezuma Valley, is located in the southwest <br />corner of Colorado within Montezuma County, <br />The City of Cortez, centrally located in the <br />project area, is at an elevation of 6200 feet above <br />mean sea level. The McElmo Creek walershed <br />originates in the lower foothills of the LaPlata <br />mountains to the Easl and is bounded on the north <br />by the Dolores River Canyon Rim and on the <br />South by Mesa Verde and the Ute Mountain to <br />the Southwest. McElmo Creek is a tributary to <br />the San Juan River. <br /> <br />The McElmo Creek basin, having a limited <br />watershed area, is a relatively dry basin under <br />natural conditions. Montezuma Valley lITigation <br />Company (MVIC), the major user and distributor <br />of irrigation water, diverts approximately 116,000 <br /> <br />acre feet of Dolores River water annually (1957- <br />1973 data) into the Montezuma Valley. Diverting <br />water from McPhee reservoir on the Dolores <br />River through a tunnel and extensive canal <br />system, MVIC presently distributes water to <br />approximately 29,000 acres. Return flows from <br />irrigation and municipal discharges constitute <br />most of the continuous channel flow in McElrno <br />creek. <br /> <br />C, Salinity in the McElmo Creek <br />Project Area <br /> <br />Mancos Shale underlies much of the Montezuma <br />Valley. This shale is of marine origin with a high <br />salt content, and provides the main salt source for <br />the return flow inlo McElrno Creek. Excessive <br />irrigation and seepage from delivery systems <br />cause deep percolation. This water dissolves <br />salts, which move downward until they reach <br />McElmo Creek, then the San Juan River, and <br />finally the Colorado River. <br /> <br />D. Climatic Conditions <br /> <br />The fanns range in elevation from 5,800 to 7,000 <br />ft. above sea level. The temperature range is <br />from 100'F to -20'F. The annual precipitation is <br />nearly 12 inches, including snowfall. <br /> <br />Two weather stations are being used to collect the <br />climatic data for the project area, The southern <br />most station was used for the 1994 monitoring <br />season. <br /> <br />E. Objectives of the M&E Program <br /> <br />I. To monitor and evaluate changes in salt <br />loading entering the Colorado River System <br />after the implementation of improved <br />irrigation systems on agricultural land within <br />the McElrno Creek Project Area. <br /> <br />McElrno Creek Unit M&E 1995 Report <br />Page 3 <br />