Laserfiche WebLink
The reservoir outlet works to Cimarron River has a capacity ranging from 160 to 280 cfs, depending on <br />the reservoir elevation. The surface area at the normal maximum water level is 293 acres. The reservoir <br />holds an absolute storage right for 14,000 acre-feet and a conditional right for an additional 30,600 acre- <br />feet (see Table 1). Other project features include the 3.6-mile Bostwick Lateral and several miles of <br />drains. <br />The Cimarron Canal is used to deliver supplemental irrigation water from Silver Jack Reservoir to <br />project lands situated under the canal, the Bostwick Park area, and the Cedar Creek area under the <br />Hairpin Lateral. Most of the shareholders in the Cimarron Canal Company own contract rights to project <br />water from Silver Jack Reservoir. One exception is the City of Montrose, which does not receive <br />reservoir storage water because municipal use is not authorized for the project. <br />Because of its high elevation, Silver Jack Reservoir is inaccessible during the winter months. During <br />these months, the outlet valve is set to release at a rate of 17 cfs, which is the approximate rate of inflow <br />during the mid-winter months. This continuous release maintains a minimum streamflow on the <br />Cimarron and limits the accumulation of storage during the winter. By late spring, the inflows increase <br />and the reservoir is usually filled by mid May. In late July, when the natural flow of Cimarron Creek <br />begins to drop off such that the Cimarron Canal cannot satisfy the irrigation demands using its direct <br />flow water rights, storage water is released from Silver Jack to supplement the direct flow diversions. <br />During the summer months, Silver Jack is operated such that a minimum streamflow of 25 cfs below the <br />head gate of the Cimarron Canal is maintained, if possible. There is also a general understanding that <br />1,500 acre-feet of the active storage capacity has been reserved by the USBR to assist in meeting this <br />instream flow objective. The right to this storage may have been conveyed to the Colorado Division of <br />Wildlife. It is also uncertain whether the project participants can encroach upon this 1,500 acre-feet for <br />supplemental irrigation water, if needed. Documentation supporting this storage allocation or its use was <br />unavailable. <br />Operation of Cimarron Water Rights in the CRDSS Program MODSIM <br />The following discussion describes the key assumptions used in the CRDSS wate r rights planning model <br />(MODSIM) to simulate the operations of the Cimarron Canal and the Bostwick Park Project (Silver Jack <br />Reservoir). <br />The irrigation demand under the Cimarron Canal, Bostwick Park, and Hairpin Lateral is based <br />? <br />on a total irrigated acreage of 7,390 acres, as determined by the USBR/DWR. Of this amount, <br />24 percent of the land is in the Cimarron River drainage, and irrigation return flows are <br />assumed to return to the Cimarron River/Gunnison River. The remaining 76 percent (Bostwick <br />Park and Hairpin Lateral) are in the Uncompahgre River drainage. <br /> <br />Based on conversations with the BWCD, the Cimarron Canal is assumed to operate at its full <br />? <br />physical capacity from May through September. Diversions are made using the direct flow <br />water right priorities shown in Table 1. If the direct flow yield is less than the 145 cfs capacity, <br />storage releases from Silver Jack Reservoir occur. <br /> <br />Of the water that is diverted by the Canal, 13 percent is delivered to the City of Montrose at <br />? <br />Cerro Reservoir and is subsequently available to meet Project 7 domestic water demands. The <br />remaining 87 percent is used to meet the irrigation demand in the system based on the 7,390 <br />acres. Irrigation return flows are assumed to occur with 76 percent to the Uncompahgre River <br />and 24 percent to the Gunnison River. <br />3 <br />A275 01.09.95 1.15-19 Fosha, Hyre <br />