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<br />DESCRIPTION OF THE STUDY AREA <br /> <br />Colorado River near the Colorado-Utah state line <br />(4,095-ft elevation). <br />In the course of its journey, the. Dolores flows <br />through five major western life zones, from the alpine <br />at its headwaters to the upper sonoran along much of <br />its lower reaches. Flows in the river vary seasonally. <br />High flows result from spring snowmelt in the <br />headwaters of the <br />Dolores and San Miguel <br />Rivers and in the La Sal <br />Mountains of Utah. High <br />intensity thunderstorms <br />also cause localized peak <br />flows intermittently <br />during July, August, and <br />September. Tributaries <br />are ephemeral or inter- <br />mittent, except for those <br />draining high mountain- <br />ous areas. <br />For purposes of <br />intensive river corridor <br />management, BLM <br />(1990) has recognized <br />two primary zones along <br />the river. These zones <br />coincide with the <br />separate floating trip <br />reaches traditionally <br />described as "upper <br />river" and "lower river" <br />(Figures 2, 3, and 4). <br />These zones also reflect <br />distinctive characteristics <br />of geology, vegetation, <br />and hydrology. Zone I, <br />according to BLM (1990) <br />is from Bradfield Bridge <br />to the Disappointment <br />Creek confluence. Zone <br />2 is the reach from the <br />Disappointment Creek <br />confluence to Bedrock <br />and includes the Dolores <br />River Canyon Wilderness <br />Study Area. <br /> <br />Overview of Study Area <br /> <br />The Dolores River is a major tributary to the <br />Colorado River, draining a northwest-southeast basin <br />covering roughly 4,100 square miles in southwestern <br />Colorado and 520 square miles in east-central Utah <br />(Figure 1). The river flows for more than 200 miles, <br />starting high in the San Juan Mountains (14,256-ft <br />elevation) and descending to its confluence with the <br /> <br /> <br />Index Map <br /> <br /> N <br /> 1 <br />10 0 10 20 30 Miles <br />I I I I I <br /> <br />Figure 1, Dolores River Basin. <br /> <br />9 <br />