7750

• UCREFRP Catalog Number: 7750
• Author: U.S. Bureau of Reclamation.
• Title: Study of Alternative Water Supplies for Endangered Fishes in the "15-Mile Reach" of the Colorado River.
• USFW Year: 1992.
• USFW - Doc Type: \
• Copyright Material: NO

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CHAPTER III
GAINS ALONG THE REACH
Observed Gains Along the Reach
In the draft of this report, an effort was made to estimate the return flows along the Reach
from previous work done as part of the Grand Valley Salinity Control Program. Since the
draft report was prepared, a new gage has been installed at the upstream end of the Reach
and periodic water measurement has been conducted near the terminus of the Reach.
Consequently, it is possible to calculate the returns along the Reach with a much higher
r degree of confidence than was used in the draft report. The original methodology remains in
this report for comparison purposes only.
Daily flow data for the month of August 1991 for the Palisade gage and the water
measurement performed through the Recovery Program by Richard D. Piland and Associates
was analyzed.' The average gain for the month was 204 cfs with a peak daily gain of 311
' cfs and a minimum gain of 140 cfs. The average daily flow at the Palisade gage for the
month was 803 cfs. The data for the Palisade gage was based upon USGS unadjusted flow
measurements. The actual flows may be slightly different. The information from Piland and
Associates was also preliminary data. The estimated average gains of approximately 160 cfs
reasonably agrees with the observed 200 cfs gains.
Estimated Gains Along the Reach
Irrigation
The distribution of irrigation water was broken into various components: canal and lateral
seepage, canal and lateral administrative spills, on-farm ditch seepage, consumptive use by
phreatophytes (both crops and growth along ditches), deep percolation of excess water
applied to fields, return flows (runoff) from irrigated lands, and evaporation. In the Grand
Valley, only the consumptive use and evaporation components fail to return to the river. The
seepage components return to the river as ground water. Studies conducted by Reclamation
for the Salinity Project have demonstrated that some of the irrigation seepage is returned to
the Reach.2
1
' Preliminary data for August 1991, Richard D. Piland and Associates, September 27, 1991.
s U. S. Bureau of Reclamation. April 1986. Water Resources Technical Supporting Data for the
' Verification Memorandum, and May 1986, Cobble Aquifer Investigation. Studies conducted as part of the
Colorado River Basin Salinity Control Project, Grand Valley Unit, Stage Two.
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