CRDSS_Task2-09-20_SummationCUEstimates_ColoBasin

• Title: CRDSS Task 2.09-20 - Summation of CU Estimates ‎(Irrigation and Other Uses)‎ for Selected Basins Within the Colorado River Basin for calender year 1985-1990
• Description: This task memorandum summarizes the results of consumptive use ‎(CU)‎ for irrigated areas and other uses ‎(livestock, stockponds, municipal, thermal electric, mineral resources, and export)‎ associated with the Yampa, White, Upper Colorado, San Juan, and Dolores River Basins.
• Decision Support - Doc Type: Task Memorandum
• Date: 1/21/1997
• DSS Category: Consumptive Use
• DSS: Colorado River
• Basin: Colorado Mainstem
• Contract/PO #: C153658, C153727, C153752
• Grant Type: Non-Reimbursable
• Bill Number: SB92-87, HB93-1273, SB94-029, HB95-1155, SB96-153, HB97-008
• Prepared By: Riverside Technology inc.

In the process of doing the pro- ration between the areas being modeled by
structures and the total irrigated areas calculated based on the GIS maps, two
issues were discovered. First, the areas represented by the structures could
have a different crop distribution than the total irrigated areas (this is more likely
when the percentage of area modeled is small). The second issue relates to the
fact that we used the location of the diversion structures to determine what
county /HUC to use for the weather stations. The GIS method used the location of
the lands to determine what county /HUC the lands served by a diversion
structure are located. When determining what percentage of a county /HUC is
being modeled we sum all the areas associated with the structures being
modeled in a given county /HUC. If the lands and the diversion structure that
serves them are not located in the same county /HUC an error would be
introduced in determining the percentage of land being modeled. Also, the
weather stations to use for a structure would change. It would be better in the
future to assign county /HUC locations to the diversion structures based on the
location of the majority land -area served by each structure and not the location of
the structure.
3.0 RESULTS
3.1 Upper Colorado River Basin
3.1.1 Crop Consumptive Use
The total irrigated lands, lands being modeled and percentage of lands being
modeled for each county -huc are shown in Table 1. This information can be used
to evaluate the validity of pro -rated estimates of CU and amounts of water
shortage in a county -huc (i.e., whether the county -huc combination is adequately
modeled by the diversion structures). Tables 2 and 3 show the amount of water
short, and the estimated crop CU by county -huc combination.
The crop consumptive use and amount of water short in a county -huc
combination are estimated using the results of CU calculations at the structure
level. The 6 -year annual average estimated CU (for the diversion structures
being modeled) is 235,285 acre -ft which pro -rated to the total irrigated areas in
the 14 county -huc combinations being modeled becomes 341,170 acre -ft. The 6-
year annual amount of water short for the diversion structures being modeled is
39,968 acre -ft which pro -rated to the total irrigated area in the 14 county -huc
combination being modeled is 60,429 acre -ft.
3.1.2 Other Uses
The CRDSS CU model is implemented using the Upper Colorado River Basin
database. CU estimates for the livestock, stockpond, and municipal are obtained
for the Upper Colorado River Basin. The data for reservoir, thermal electric, and
mineral were obtained from the USGS by HUC. The export category was
obtained from the state engineers office.