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<br />Project Service Area and Facilities
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<br />The Silt Water Conservancy District is located in west central Colorado near the towns of Rifle
<br />and Silt (combined area population of about 8,000). The District stores flows from Rifle Creek
<br />and pumps water from the Colorado River to increase the available irrigation water for 6,591
<br />acres ofland, For purposes of this plan, reference to the Silt Project will include this principle
<br />features: Rifle Gap Dam and Reservoir, Harvey Gap Dam and Reservoir, Grass Valley Canal,
<br />Davie Ditch, silt pumping plant (pumping from the Colorado River), a lateral system, and other
<br />associated features. During construction of the Project, existing canals and laterals were used
<br />and rehabilitated where necessary, Recreation facilities have been constructed at Rifle Gap
<br />Reservoir and some facilities are available at Harvey Gap Reservoir. Water measurement
<br />structures are used at these features to determine proper distribution of project water to the
<br />private laterals, however some structures are in need or re-calibration or repair.
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<br />The District stores water in Rifle Gap Reservoir, formed by Rifle Gap Dam on Rifle Creek and
<br />in Harvey Gap Reservoir. Reservoir exchange releases are made from Rifle Creek to existing
<br />ditches to meet downstream irrigation needs, Flows from Rifle Gap Reservoir are measured and
<br />recorded with a Parshall Flume and Steven's type float recorder. However, during spring run-off
<br />when the reservoir is spilling, the flume is typically inundated so the total flow is not measured
<br />properly. Harvey Gap Reservoir is filled through the Grass Valley Canal, which is diverted from
<br />East Rifle Creek near Rifle Falls, Flows from Harvey Gap are also measured through a Parshall
<br />Flume and the data in manually recorded.
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<br />Some project water is released directly from Rifle Gap Reservoir into Davie Ditch, to supply
<br />irrigation water to project lands on Davie Mesa, The majority of reservoir releases are made to
<br />meet downstream diversion rights of non-project lands. These releases allow additional
<br />diversions from East Rifle Creek upstream from Rifle Gap Reservoir for Project use, Delivered
<br />through the Grass Valley Canal, this exchange water provides a full irrigation supply for land
<br />that was not irrigated before the Proj ect and a supplemental supply (supplements non-proj ect
<br />water) to project lands previously irrigated with Harvey Gap Reservoir water and Grass Valley
<br />Canal diversions, Flow from East Rifle Creek is diverted into the Grass Valley Canal just below
<br />Rifle Falls, The canal, located on a steep sideslope, is over 6 miles long and was built to carry
<br />approximately 60 cubic feet per second (cfs), Due to landslides, ditch bank settlement,
<br />vegetation growth, and seepage, its current capacity is somewhat less, It flows through two 48"
<br />diameter siphons that were last replaced sometime in the 1940's and three tunnels, Both the
<br />canal and the siphons leak or seep at different locations, Due to the canal's location on the steep
<br />hillside, the canal cannot be accessed in some places with a vehicle or machinery,
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<br />The Dry Elk Valley lateral carries water from the Grass Valley Canal to both full and
<br />supplemental service lands in Dry Elk Valley, The water in the Dry Elk Valley lateral is
<br />measured through a Constant Head Orifice (CHO) measuring device, which may not be
<br />operating properly, Some structural modification may be necessary so that it measures correctly.
<br />Under project operation, Harvey Gap Reservoir, which previously filled and emptied each year,
<br />now stores and regulates water for a longer irrigation season,
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<br />The Silt Pumping Plant, with a capacity of 36 cubic feet per second, is located near the Colorado
<br />River about 2 miles east of the Town of Silt. The Colorado River diversion for the pumping
<br />plant was constructed along with the other project facilities in the mid-1960's, The pumping
<br />plant was designed to provide irrigation water (both supplemental and full service) to the lower
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<br />Silt Water Conservancy District
<br />Silt Diversion Project Feasibility Study
<br />January 2000
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<br />Page 7 of 15
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