WSP07539

• File Number: 8281.300
• Description: Colorado River Studies and Investigations - Colorado River Consumptive Uses and Losses Report
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/1/1991
• Title: Consumptive Uses and Losses in the Arizona Portion of the Upper Colorado River Basin for the Water Year 1990
• Water Supply Pro - Doc Type: Report/Study

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Consumptive Uses and Losses

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BIA Water Systems.-Wells developed and operated by the BIA serve
nujnerous Navajo communities. These systems also serve BIA schools,
hospitals, agency offices, and some housing on the reservation. Metered records
for. total amounts of water pumped from BIA wells were available for a portion
of the Shiprock Agency, the Western Navajo Agency which is considered to be
the Tuba City Agency, and the Chinle Agency. Figure 1 shows the agency
boundaries within the Upper Colorado River Basin.

The uncertainty was estimated to be about 7 percent for all three agencies.
The resulting values appear in table 2.

The BIA systems include sewage disposal units terminating in lined
evaporation ponds with very little or no return water returning to the
ground-water system. Undoubtedly, some losses occur in distribution, but
insufficient data currently exist to estimate these losses. The losses are
probably less than the uncertainties for each of the reported values.

The BIA well data available fOl: the Shiprock Agency include Cove,
Red Rock, and Teec Nos Pos. Total consumptive use values (shown in table 2)
are 70 (:1:10) acre-feet.

Pumping records for the Western Navajo Agency include data for the cities of
Chilchinbeto Day School, Dennehotso Boarding School, Kaibeto Boarding
School, Kayenta Boarding School, Navajo Mountain Boarding School, Red Lake
Day School, Rocky Ridge Boarding School, Shonto Boarding School, and the
TlJba City Headquarters. Total consumptive use for the Western Navajo
Agency was 630 (:1:40) acre-feet in 1990.

Well pumping records for the Chinle Agency include data for the following
schools: Cottonwood Day School, Low Mountain School, Lukachukai School,
Nazlini School, Rock Point School, and Many Farms Schools. Two schools,
Pinon and Rough Rock, maintain their own records, but data for these two
schools were included with the Chinle Agency data. Total consumptive use for
the Chinle Agency was 330 (:1:20) acre-feet, (shown in table 2).

Navajo (WOM) Water Systems.-Estimated water use in 1990 by the Navajo
WOM service areas was based on an assumed consumption rate of 160 gpcd.6
For a 1990 estimated service-area population of 3,080, the estimated
annual water use was 550 (:1:170) acre-feet. The uncertainty is estimated
as 30 percent of the total.

. Communication with Peter Deswood, Executive Director, Division of Water Resources of the
Navajo Nation, January 31, 1985.