9344

• UCREFRP Catalog Number: 9344
• Author: Camp Dresser & McKee Inc.
• Title: Replacement of the Plateau Creek Pipeline.
• USFW Year: 1996.
• USFW - Doc Type: Denver.
• Copyright Material: NO

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value has been used to provide estimates of water availability. For rights already adjudicated and
currently used for domestic purposes, a S percent CU rate is used.
It is important to note that the SO percent CU rate assumed does not imply that the District will divert
SO percent of the decreed rate of a right, but rather only SO percent of what that right has historically
diverted for agricultural use. For example, the District owns 1.625 cfs in diversion rights in the
Welch Ditch on Coon Creek. If the rights diverted year-round at this rate, they would divert 1176
ac-ft. However, historical irrigation diversions have only occurred in April through October,
averaging about 274 ac-ft/yr. At the SO percent rate, the District will divert an average of 137 ac-
ft/yr after the transfer, or less than 12 percent of the total volumetric decreed capacity of the ditch.
Any remaining water which the rights would have diverted historically must be left in the stream to
satisfy junior and conditional water rights which are entitled to protection of stream flows that reflect
historical conditions.
CU diversions are shown in Tables 3.1 and 3.2 as CU diversions to Ute Water (or WTP) and CU
diversions by agriculture. Under baseline conditions, only the Mason and Eddy Ditch right is being
utilized by Ute Water for municipal purposes, providing S09 ac-ft/yr. However, the District's other
agricultural rights have diverted a CU rate of 623 ac-ft/yr for irrigation and domestic use. Under the
future scenario, all District rights will be transferred with 1132 ac-ft/yr available for diversion to the
municipal system. However, modeling results indicated that the 623 ac-ft/yr of CU water diverted
to agriculture under baseline conditions will not always be fully utilized for municipal use under
future conditions. Though in many years the full amount will be utilized, an average of 129 ac-ft/yr
will not be diverted when excess supplies prevent full utilization of all supplies. Note that the CU
diversions result in no net future depletions to the basin, since diversions will be limited to historical
CU. Under Scenario C, net depletions will actually be 129 ac-ft/yr less due to under-utilization of
the transferred water. While it is true that diversions by these rights result in depletions to the
streams, such depletions have historically occurred from their former use and are not a result of the
District's operations.
3.2. S Jerry Creek Reservoir Evaporation
Net evaporation from the Jerry Creek Reservoirs adds to the overall depletion to the Colorado River
system. Net evaporation is estimated as the additional evaporation that results from the operation
of the reservoirs, which is in excess of the normal evapotranspiration that would occur without the
existence of the reservoirs. Precipitation over the surface of the reservoirs is also considered in
calculating net evaporation.
The Jerry Creek Reservoirs are generally utilized only under drought conditions and remain nearly
full at all other times. Evaporation averages 670 ac-ft/yr under baseline conditions. Under future
conditions, the reservoirs would be utilized more frequently due to larger demands. This results in
less full reservoirs,~less exposed surface area, and reduced evaporation. This is indicated by the
slightly lower average evaporation of 661 ac-ft/yr in the future scenario resulting in a minimal
decrease in net depletions.
CDM Camp Dresser & McKee
0:18047-I 101DOC1APPEND-B.DOC B-S