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presented in lorns et. el. (1965b), over 51,000 acres were irrigated to the Yempe River Basin above Meybell, Colorado in 1957. At that time, the total annual TDS discharge was estimated et 218,800 tons, end trrige[ion accounted for 13.6 percent (29,800 tons) of the total annual TDS discharge. Site Soeci}ic Surface Yeter Information Drainece Basin Geomoroholoev. Two principal drainages receive ell the runoff from the general Yoest mining area. The principal drainages are Sege Creek and Grassy Creek. For the proposed first five-year Yaest mining plan, two tributaries (Annand Draw and 011 Drew (NPDESII)) confluent with Grassy Creek will have some mining disturbance in their watersheds. For the sake of completeness in the Hydrologic Description, three other drainages (Y1 Drew (NPDES 12); Y2 Draw (NPDESI3 ), and Y3 Draw (NPDE514) tributary to Sage Creek could be disturbed by potential mining activities beyond the first five-year mining plan. The two principal drainages end the five tributaries identified by NPDES numbers are ell shown on Exhibit 7-1. An NPDES permit will be secured and NPDES sites will be established on Annand Draw and 011 Draw prior to the initiation of mining. • The drainage basin geomorphology of the five draws previously identified has been evaluated. Table 7-29 summarizes measurements of select geomorphic parameters for the five draws. The geomorphic parameters were aLl determined from 1" = 1000 scale maps (USGS topo) and are partially a function of the degree of resolution obtained from such. The entire watersheds for each draw, excepting Annand, were evaluated. The Annand watershed investigated extends from the Nof stger Zeigler Reservoir tributary confluence in Section 4, TSN, R87Y to the basin divide in Section 20, TSN, R87Y. Computational methodologies are footnoted. The geomorphic data summarized in Table 7.29 indicate the drainage patterns exhibited in the five draws are a combination of parallel (slope and structure control) and dendritic. The drainage densities are moderate (7.26 to 10.38 mi/mi2), the channel sinuosities are low (1.01 to 1.07 mi/mi ), end the channel gradients ere moderate to steep (0.039 to 0.218 ft/ft). The drainage density, constant of channel maintenance end lemniscete ratio ere similar in that they ell provide an indication of the storeg e, flow characteristics, and general efficiency of the basin end the channel network. The lemniscete ratio was used rather • then the circularity ratio because basins would more typically be pearshaped then circular. The constant of channel maintenance values (0.096 to 0.138 mil/mi) ere not greatly different considering the range of drainage areas (0.08 to 1.59 mi2). Those 87