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<br />'" <br /> <br />Description of Study Area <br /> <br />o <br /> <br />The Arizona portion of the Upper Colorado River Basin is located in <br /> <br />N <br />c:o <br />C,C) <br />t.Q <br /> <br />the northeast corner of Arizona and comprises an area of 6,927 square miles. <br /> <br />See Figure 1. Nearly all of this area lies within the boundaries of the <br /> <br />Navajo Indian Nation. The only town of significant size is the Glen Canyon <br /> <br />Dam community of Page. <br /> <br />Terrain within the study area is composed predominantly of plateaus <br /> <br />and mesas, bordered by cliffs and steep slopes, The sandy soil mantle <br /> <br />supports a sparse growth of grasses and sagebrush at lower elevations and <br /> <br />pinyon-juniper and scattered conifers on the higher slopes and in the <br /> <br />mountains, Primary land use is grazing. <br /> <br />Normal annual rainfall over the study area averages about 9 inches <br /> <br />with extremes of 6 inches at Page and over 20 inches in the Chusca Moun- <br /> <br />tains. The few intermittent streams draining the area are bordered by <br /> <br />narrow alluvial valleys, Wind and water erosion are prevalent. <br /> <br />Hydrologic Conditions in 1973 <br /> <br />Drought conditions were eased during the 1973 water year by the occur- <br /> <br />rence of heavy rains in October 1972 and by above average snowmelt runoff <br /> <br />flo"s during April, May, and June of 1973. <br /> <br />Monthly precipitation records of meteorological stations in and near <br /> <br />the Arizona portion of the Upper Colorado River Basin are summarized in <br /> <br />Table 2, Water year totals are "ell above average due to the October, 1972 <br /> <br />stOl1llS, HO\,C'ver, precipitation during the 1973 gro"ing season was below <br /> <br />ave'rage at most of the r0purting 'stations. <br /> <br />~k1l1Ully tl...\tllperaturc records arc summarized in Table 3. N('un annual. <br /> <br />t'('\~lrH.'l'<.ll:lIr~.:~s dllLing 1973 ~.'!("re below nvel:-age. <br /> <br />2 <br />