2012-06-20_PERMIT FILE - C2010089A (9)

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GENERAL HYDROLOGY Regional Surface Water. The drainages in the NHN general area are developed on the incised Nucla Syncline and are greatly affected by the dip slopes of that structure. Map 2.04.5 -1 shows the locations of the streams and drainages of primary interest. Coal Creek Canyon drains the largest portion of the permit area and the area immediately to the east, north, and west of the permit area. Tuttle Draw drains the southern portion of the permit area and the area immediately to the east, south and southeast of the permit area. Both Coal Creek Canyon and Tuttle Draw drain to the west into the San Miguel River. The area is semi -arid receiving an average of 12.5 inches per year (1960 -2009) at the Uravan site, (see Section 2.04.8 Climatological Information of this permit application). Surface water flow in the vicinity of the permit is therefore primarily dependent on surface irrigation. The Colorado Cooperative Ditch Company (CCC) brought water into the permit area in 1905 and Map 2.04.5 -1 shows the location of primary irrigation ditch, the 2 Park Ditch located to the northeast of the permit area, and secondly the 2nd Park Lateral Ditch. The 2 Park Lateral is constructed along the divide between the tributary drainages of Coal Creek Canyon and Tuttle Draw and carries water across the permit area. Irrigation in the general area is primarily "flood irrigation ". The primary drainages in the permit area are referred to in this permit as Glasier Draw and Meehan Draw (both tributary to Coal Creek Canyon, draining the northern portion of the permit), and Nygren Draw (tributary to Tuttle Draw and draining the southern portion of the permit) as shown on Map 2.04.5 -1. These draws serve as returns of runoff and seepage from the 2 Park Ditch and Lateral to the surface water system. The irrigation season is typically from mid April to early October. With the exception of severe thunderstorm events, surface water flow and quality in the general permit area are dependent on the irrigation system. Surface Water Flow. A discussion on surface water flow in the permit area starts with the San Miguel River. The San Miguel derives the majority of its flow from snow melt runoff although some water is contributed by severe summer thunderstorms. The San Miguel River at Naturita, Colorado has a drainage area of 1,080 square miles. USGS Surface Water Records for the San Miguel at the Brooks Bridge (0.5 mi. upstream of Nucla Station) show the mean flow of 252 cfs for Water Year of 2009 and a mean flow for Calendar Year 2008 of 316 cfs. The mean flow for water years 1995 -2009 is 247 cfs with lowest mean for the period of 59.1 cfs which occurred in 2002. The highest mean flow for the period is 499 cfs which occurred in 1997. The highest daily mean flow for the 1995 to 2009 period was 2,370cfs which occurred on 6/17/1995. This compares with the highest daily mean flow at Brooks Bridge for Water Year 2009 of 1,630cfs occurring on 5/13/2009. The CCC ditch diverts about 100cfs from the San Miguel River upstream from the Brooks Bridge. The Colorado Cooperative Company records show that during 2009 that 19.20 cfs (8617 gpm) was delivered to the lower end of the ditch. About 10.5 cfs (4712 gpm) of the total flow was diverted above the NHN permit area leaving about 8.7 cfs (3905 gpm) to flow into the NHN permit area in the lower 2 Park Lateral. Irrigation water runs off and seeps into the drainages resulting in flows in Glasier Draw, Meehan Draw, and Nygren Draw. Surface water monitoring (see section 2.04.7 of this permit) Section 2.04.5 Page 4 April 2011