WSP00132

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications-Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1980
• Title: Use of Saline Water in Energy Development
• Water Supply Pro - Doc Type: Report/Study

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flow averages 93 gpm and therefore is too
small for B major supply, but keeping even
this much salt out of the Green River would
have significant benefit. The geyser is
located near Green River, Utah, very close to
planned coal and possibly nuclear powered
generating plants.

One of the largest single point sources
of salt on the Upper Colorado is a group of
springs near Ootsero, Colorado~-which average
14,200 mg/l for a flow of 16 cfs.

Groundwater

Quali ty. Groundwater data for the
basin are very limited except in localized
areas. Even though there have been hundreds
of wells drilled in the basin over the years,
most of these were drilled for oil or gas,
and information pertaining to the presence of
water or its quality were generally not
recorded. The U.S. Geologicsl Survey has
examined many hundreds of oil and gas well
logs within the basin, and extracted whatever
water data they could ident ify, and all of
these were made available to the current
study (Appendix A). In addition, data and
information from other available sources were
obtained.

The total amount of high TDS (low
quality) groundwater existing in the study
area is extremely large (many millions of
ac-ft); however, economic and environmental
factors may limit their use. For example,
much of the brackish water is overlain with
fresh water. Wells to develop brackish water
can be perforated in only the brackish water
depths, but long terln pumping of some such
wells may leak fresh water into the brackish
portion of the aquifer, This will decrease
the availability of fresh water for other
purposes and thereby obviate the extra costs
associated with developing the brackish
water.

Because of the large size of the Upper
Colorado River Basin and the time and finan-
c ial constraints of this study, only water
quality situations in the vicinity of eco-
nomically significant coal deposits have been
mapped (Figures 6 through 11).

At least two serious deficiencies exist
in the data shown: 1) Very little informa-
rion is available concerning the depths from
which the samples came. Some of the wells
are 10,000 feet deep, and the water quality
shown may be of water near the surface, very
deep, or a composite of the entire geologic
profile. 2) With few exceptions, no informa-
t ion is available concerning quantities of
existing groundwater or the amount of the
total that can be recovered. Some estimates
have been made by people familiar with
aquifer conditions in the area, but the cost
of pumping tests to obtain more data is
greatly beyond the acope of the present
study,

~uantitY' Even without making a de-
taile inventory, it is evident that the
amount of brackish and saline water in the
basin is very large. As, a general rule
salinity of groundwater increases with depth
as is indicated by actual measurements, shown
in the three-dimensi,onal map in Figure 12.
Work done by Feth et a1. (1965) (Figure 1)
indicates that about two-thirds of the study
area is underlain by water containing in
excess of 1,000 mg/l TDS at less than 500
foot depths. Figure 2 shows that according
to best estimates, this saline water is not
overlain by fresh water in about one-third of
the Upper Colorado River Basin.

One possible approach to estimating
quantities of brackish water is the analysis
of electrical resistivity logs from oil and
gas test holes. For example, such well logs
were used in Louisiana to map the depths to
various groundwater salinity thresholds
(Turcan and Winslow 1970). The concept used
wae to estimate a representative formation
resistivity factor Rf and then calcula-te
water resistivity Rw (from which TDS can be
estimated) as the ratio of the well log re-
sistivity to the formation resistivity factor
(Rw ~ Ro/Rt). In Louisiana results were
reasonably accurate within the lower salinity
ranges 00,000 mg/l and below). However,
considerable effort was required in that it
was necessary to screen 200,000 well logs
to select a sample of 1,000 representative
logs; then to analyze that sample by quan-
t ifying the following variables: depth, log
resistivity, changes in geologic formation
with depth, temperature (for correcting
resistivity/TDS factors), porosity, and
permeability of each formation.

This level of effort was not undertaken
for the Upper Colorado River Basin for
this study for the following reasons:

1. Analysis of resistivity logs re-
quires a specialist with an understanding of
both the geologic formations and the anoma-
lies which occur in resistivity levels as the
geology and water occurrence and quality
change with depth. The use of such special-
ists for the extended period required to
analyze many hundreds of well logs was not
possible within the budget limitations of
this study.

2. If the water TDS levels had been
successfully mapped, it would then be
necessary to associate each quality reading
with estimated formation porosity in orde< to
estimate the volume of water in each quality
renge in each aquifer. One would then
proceed with estimated permeability in order
to estimate the rates of flow possible from
wells in areas and at depths of interest,
The perlneability of the Colorado Plateau
sandstone varies over several orders of
magnitude making estimates questionable
unless actual permeability field tests have
been made (see item 3). For example, the
Navajo sandstone specific yield (which is

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