WSP02036 - Laserfiche WebLink

Home Browse Search

00 C:.J M CHAPTER III WATER SUPPLY Water Resources Streams and Watersheds Of the three strealIJ3 which form main Rifle Creek, East Rj.fle Creek is by far the mst productive. The average elevation of East Rifle Creek watershed is much higher than that of the other two tributaries. The East Rifle Creek watershed is underlain by cavernous limestone which Permits natural underground storage. The stream is fed princi- pally by a large number of springs of relatively constant flow. These conditions contribute to make the base flow of East Rifle Creek unusually high.. The minimum mean daily discharge recorded during 7 years of record was 24 second-feet while the mean annual discharge is about 40 second- feet. In contrast to the run-off of East Rifle Creek, the run-off of Middle and West Rifle Creeks, draining the lower elevations of the dra,inage area, is low per unit area and is sporadic in occurrence. Approximately half of the annual run-off of these two .tributaries occurs during the months of April and May. ~ , :'~ Run-off and Diversion Records ., ... Two stream gaging stations were maintained to furnish data for water supply studies. One gage was located on Rifle Creek immediately downstream from the ~e GI!IUJ_8.I!I. site. This gage was maintained for 7'years, from 1940 to 194b:" It measured flow from a 140-square mile drainage area, .modified by diversions to Grass Valley Canal. The second gage was on ;East Rifle C~~.t immediately above the Grass Valley Canal diversion and below-theRifle Falls Power Plant. This gage was main- tained through the 7-year period, 1937 to 1943. It measured the flow "from a 32-square mile area, modified by diversions to three small irri- gation ditches. The power plant operate s without storage control and has little effec.t on instantaneous discharge and no effect on mean daily discharge. :,~ '"~. ".: ;-'; The principal diversion from East Rifle Creek is into Grass Valley Canal. Diversion records have been obtained for this canal from daily readings of a staff gage dur ing the irrigation season. Although the canal diverts water ruost,::!the year, almost no data are available during the nonirrigation season. '>,: Nineteen ditches besides the Grass Valley Canal divert irrigation water above the Rifle Creek gage. These small diversions are from all three of the upper tributaries and return flow reaches the main stream lS