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<br />.~ <br />,~,;,'j <br />~....,,:.> <br /> <br />2 <br /> <br />OVERVIEj{ OF THE STUDY AREA <br /> <br />l\:) <br />-..] <br />o <br />:"1" POLITICAL AND HYDROLOGICAL SUBAREAS <br /> <br />~'f~~E~ <br /> <br />~:::r. <br /> <br />As defined by the U.S. Water Resources Council (WRC) , the Upper <br />Colorado River Region (hereinafter called "the R" ~i",n") includes the Upper <br />Colorado River Basin and the Great Divide Basin, which is a closed basin <br />in Wyoming. 1 Total drainage area of the Region, which covers about 45 <br />percent of the Colorado River Basin, is 113,496 square miles (72,600,000 <br />acres). Dimensionally, the Region extends about 550 miles north-south <br />and 350 miles east-west to encompass portions of the States of Wyoming, <br />Colorado, Utah, New Mexico, and Arizona. <br /> <br />The Region may be disaggregated to. the usual political sub- <br />divisions (States, counties, etc.) or physical subdivisions (river <br />basins, watersheds, etc.). With respect to political subdivisions, this <br />report will refer to the multicounty "aggregated subareas" (ASAs) used in <br />the WRC 1975 Water Ass~ssment. In this cunt~xt, the hydrologic boundaries <br />of the Region are approximated by the political boundaries of ASAs 1401, <br />1402, and 1403 (fig. 2.1). Much of the background information found in <br />this chapter, and elsewhere in this report, is presented on an ASA basis. <br /> <br />The WRC has also divided the Region into water accounting units <br />(WAUs) which are contiguous with major river subbasins in the Region, <br />(fig. 2.2). Figure 2.2 also shows those point~ that will be used to <br />represent the outflow points of each WAU. These outflow points will be <br />referred to throughout this report, especially as they. relate to hydro- <br />logic analyses. <br /> <br />For the purposes of this l3(a) assessment, WAUs in the Region have <br />been further subdivided into study subunits (SSUs). This was done in order <br />to facilitate the compilation of water deple~ion data from individual States <br />and to keep an accounting of each State's depletions. for interstate compact <br />purposes (see fig. 2.3). <br /> <br />1. Throughout this report the terms Upper Colorado River Region (or Region) <br />and Upper Colorado River Basin (or Basin or Upper Basin) are used inter- <br />changeably. While not identical areas, the difference in data that arise <br />by specifically including or excluding the Great Divide Basin are so small <br />as to be insignificant. Furthermore, the term Upper Colorado River Basin <br />as used here should not be confused with the definititon of "Upper Basin" <br />as used in the Colorado River Compact. Where the compact definition is <br />intended, the term will be given in quotation marks (see chapter 8.) <br /> <br />2-1 <br />