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and rangeland (First Park) and to a lesserextent, the townsite of Nucla, Colorado. The middle and <br />upper portions ofCalamity Draw Basin have been intensively irrigated and cultivated since the early <br />1920's and late 1910's. The development of the townsite and corresponding spread of cultivated <br />and irrigated fields has resulted in a disjointtributarydrainagepattern almostcompletelycontrolled <br />by the return ditches of the irrigation network. These return ditches (tributaries) in the mid- and <br />upper portion of Calamity Draw are mostly intermittent and possibly perennial and are largely <br />influenced by the timing and application of irrigation water. The overall average basin slope of <br />Calamity Draw is about 76 feet per mile, with an average basin elevation of 5,857 feet above MSL. <br />For the basin area in Calamity Draw above the location of surface water monitoring Site SW-N 103 <br />(see Map 2.04.7-1 Hydrologic Monitoring Site Location Map), the average basin slope is <br />approximately 48 feet per mile. This suggests that since the onset of man's activities in the upper <br />portions of Calamity Draw (cultivation of land and the establishment ofthe townsite), these activities <br />have greatly influenced the basin geomorphology of this watershed. <br />The Tuttle Drawdrainage consists ofbothnon-irrigated grazing areas and irrigated cultivated land. <br />The drainage area above Nucla and the intersection ofthe Second Park irrigation ditch and the West <br />• Lateral irrigation ditch isnon-irrigated range land developed on the more steeply dipping slopes of <br />thesouthwestflankoftheUncompraghreUplift. Tributaries to Tuttle Draw in thisareaincisethedip <br />slopes resulting in local topographic relief of up to 200 feet (Spradlin Park area). This produces a <br />moderately sloping rough mesa and canyon topography in this area with the mesa tops (dip slopes) <br />sloping to the southeast at about 320 feet per mile. Below Nucla and the intersection of the two <br />irrigation ditches, slopes are more moderate and the flatest land is irrigated. Tributaries to Tuttle <br />Draw along the northern flank of First Park typically have local topographic relief of 100 feet or less. <br />The mesa to the south of Tuttle Draw located in the revised New Horizon 2 permit area slopes <br />generally to the west at about 130 feet/mile. The lower reaches of Tuttle Draw are steeper. <br />Topographic relief at the mouth of Tuttle Draw is about 300 feet. The Tuttle Draw drainage area <br />encompasses elevations from 6580 feet to 5240 feet with an average gradient of about 140 <br />feet/mile. The stretch ofTuttle Draw thatdrains to the revised New Horizon 2 mine permitarea has <br />a gradient of about 98 feeUmile. <br />Channel Characteristics <br />The perennial nature of flow occurrence in both Tuttle Draw and Calamity Draw in the vicinity of <br />• (REVISED6/28/01) 2.04.7-23 <br />