CRDSS_Task1_14-20_EstimatingLivestock_GunnisonBasin

• Title: CRDSS Task 1.14-20 - Consumptive Use Model - Estimating Livestock in the Gunnison River Basin
• Description: The objectives of this task memorandum are to develop, describe, and use a method for estimating the number of livestock per hydrologic unit in the Gunnison River basin.
• Decision Support - Doc Type: Task Memorandum
• Date: 1/9/1995
• DSS Category: Consumptive Use
• DSS: Colorado River
• Basin: Gunnison
• 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.

the Gunnison River basin is needed. One accurate and easy approach is to use the county area
distribution in the Gunnison River basin given by the GIS 1993 data. Table 3 shows the total county area
and the portion that falls in the Gunnison River basin. Also, the percentages that fall inside the basin
divided by the total county area are shown in Table 4. Using these percentages, any quantity given per
county can be subdivided into hydrologic units, assuming the distribution of the livestock is uniform in
each county. For the livestock numbers, the assumption of uniformity of the livestock distribution will
introduce some error into the computations; but, this should be acceptable for the scope of this project.
Livestock Per Hydrologic Unit
To compute the number of livestock for the years 1985 to 1990 per livestock type from the county data
as shown in Table 2, the percentages of the area in Table 4 were used. Each number of livestock from
Table 2 was multiplied by the percentage of the hydrologic unit in that county given in Table 4. Table 5
shows the estimated total number of livestock per hydrologic unit in the Gunnison River basin. These
numbers can be used in calculating the livestock consumptive water use in the CU model in the
Gunnison River basin.
3.0 CONCLUSIONS AND RECOMMENDATIONS
For the years 1985 to 1990, the CAS recorded the total livestock numbers for the entire state only. A
method for converting these data to county and hydrologic unit was developed by the CRDSS CU team.
A weighted average from CAS 1979 to 1983 livestock data and the GIS 1993 area percentages were
calculated and used to estimate the livestock numbers for each livestock type per county and hydrologic
unit that fall inside the Gunnison River basin.
4.0 SUPPORTING MATERIALS
Table 1 shows the CAS for the 1979 to 1983 pre-county, weighted average, and the percentage per
county to the total state livestock number for each livestock type.
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