WSP07738

• File Number: 8281.970
• Description: Colorado River Studies and Investigations -- Great Basin Comprehensive Framework Study
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1971
• Title: Appendix V - Water Resources -- Great Basin Region Comprehensive Framework Study
• Water Supply Pro - Doc Type: Report/Study

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SUMMARY

The Great Basin Region is among the more arid of the 20 Comprehensive
Framework Study Regions in the United States. Hydrologic characteristics
are summarized below and discussed in more detail throughout this report.

The average annual precipitation for the Region is about 11 inches
and ranges from about 60 inches in the higher mountains in the Bear River
and Great Salt Lake Subregions to about 4 inches or less in the Great
Salt Lake Desert, Black Rock Desert of Humboldt Subregion, and in the
southern part of the Tonopah Subregion. The three eastern subregions,
which occupy about 39 percent of the 137,000 square-mile area, have an
average annual precipitation of about 14 inches and the three western
subregions, with the remaining 61 percent of the area, have an average
annual precipitation of less than 10 inches. The estimated total volume
of precipitation is 82 MAF (million acre-feet), about equally divided
between the eastern and western subregions. More than 90 percent of the
volume of precipitation is used by evaporation and transpiration without
becoming streamflow or ground-water recharge.

Runoff from mountains is about 6.2 MAF a year, roughly 7 percent of
the total precipitation. Of this amount, about 1.8 MAP is measured at
the maximum flow gaging stations on the principal streams within the
drainage areas upstream from the principal gaging stations. About 17
percent is in numerous widely distributed secondary and minor streams.

In addition to the runoff generated within the Region, 1.1 MAP of
principal'streamflowenters the Region from the California Region, and a
net import of about 0.1 MAF is diverted to the Region from the Colorado
Regions.

The principal rivers are Bear, Weber, Jordan, Sevier, Humboldt,
Truckee, Carson, and Walker. About 60 to 80 percent of the natural
annual flow in these and other streams in the Region occurs in a
3-month period starting in April or May.

Lakes and reservoirs have about 4.3 MAF of usable storage capacity
at the 1965 level of development. This permits substantial regulation
for the Bear, Weber, Jordan, and Sevier Rivers. The Truckee River is
extensively regulated through storage in reservoirs and lakes in the
Califor~ia Region.

Natural ground-water discharge from 154 valleys or areas of the
Region, exclusive of that discharged in the upstream depletion areas of
the principal streams, is estimated to be about 2.3 MAP annually. Ground
water stored in the upper 100 feet of saturated deposits of valley-fill
reservoirs is estimated to be nearly 200 MAF. Thus, the annual ground-
water discharge is a small fraction of the ground water in storage.