WSP05364 - Laserfiche WebLink

Home Browse Search

. . 9 Another instream feature is located about 3 miles upstream from the Grand Valley Irri9ation Company diversion and is known locally as the Price Stub Dam (RM 188.2). Built in the latter 19th century for irrigation purposes, the dam is 8 feet high and spans the entire width of the river. It is probable that this structure acts as an upstream barrier to fish migration during most flow stages. The final irrigation diversion on the upper Colorado River that currently contributes to seasonal flow fluctuations in known occupied squawfish habitat is the Grand River Water Users Diversion (otherwise known as Government Highline Diversion), located about 8 miles upstream from Palisade, Colorado (RM 193.6), immediately above the confluence with Plateau Creek. This diversion removes up to 1600 CFS from the Colorado River durin9 the growing season (April - October), and 800 CFS the remainder of the year. Approximately 62~ CFS of the diverted flow during the growing season, and the BOD CFS diverted during the remainder of the year are used to produce power and return to the Colorado River near Pal i sade (RM 185). The potential exists for the Colorado River to be nearly dewatered below the Grand Valley Irrigation Company diversion by the combined effects of these major diversions. During times of extreme low flow during the growing season, the diversions are cooperatively operated to maximize the use of available water. Under this cooperative arrangement, water diverted by the Government Highline diversion and used to produce power and irrigation by junior rights in the Government Highline System is returned, or "checked back," to the Colorado River upstream of the Grand Valley Irrigation Company diversion. The "checked back" water is subsequently diverted from the river at RM 185 by the latter, more senior, water right holder. The contribution of Plateau Creek and miscellaneous seepage/return flows help maintain minimum flow conditions in the reach upstream from the Grand Valley Irrigation Company facility; however, near-dry conditions have occurred in the Colorado River downstream from the Grand Valley Irrigation Company diversion during low-water years. Nearly dewatered conditions occur when flows immediately above the Grand Valley Irrigation Company diversion, including the "checked back" water of the Government Highline System, are approximately the same as the Grand Valley Irrigation Company's water right of 640 CFS (thus the river can be dewatered just below the diversion). A likely time for. low flow upstream from the diversion is late July, August, and early September. In low-water years, the result is a near-dry streambed condition for a short reach within known occupied habitat for Colorado squawfish. For 2 miles downstream from the diversion, the river slowly recovers from this nearly dewatered state by the addition of ground water and small irrigation return flows, amounting to approximately 50 CFS. Within about 5 miles downstream, it has increased to 200 CFS; and just above the confluence of the Gunnison River (15 miles downstream), it reaches 300-350 CFS (BR, 1980). Impact Below the Confl uence of the Gunnison River It is assumed that the depletions resulting from sale and use of Ruedi Reservoir Round II water will also result in some degree of reduction in flows in the Colorado River below the confluence of the Gunnison River. The