WSP05057

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1983
• Title: Colorado River Water Quality Improvement Program - Status Report
• Water Supply Pro - Doc Type: Report/Study

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Another perspective of the broad technical scope of potential control mea-
Sures can be seen in figure 7. The alternative control systems and various
components pose a number of options that require detailed. site-specific
analysis. Most of the components have proven technical feasibility, while
others. such as high-recovery desalination and underground injection may
involve technical uncertainties. Some of the point source and diffuse
source controls are dependent on technological advances in high-recovery
desalting (70- to gO-percent freshwater recovery) and related pretreatment
processes to reduce brine volume and waste disposal costs. The use of
large. lined ponds for evaporation of waste brines raises continuing concern
over the seepage protection of liner materials, service life of the liners,
and the final disposal of accumulated mineral salts.

In addition to the technical hardware considerations, control system design
is often constrained by the sheer volume of design data required. Most of
the irrigation source controls involve large areas of agricultural land
(60,000 to 100,000 acres - average size) which must be analyzed in detail
for adequate des 19n data (soi 1 s, ground water, topography, seepage areas,
ete,) .

For most of the salinity sources identified in the Basin, the sources of
the salt as well as the transfer mechanisms which add salt to the river
system are ground-water related. The ground-water systems themselves
present some unusual natural phenomena because of geothermal heating,
geologic faulting, and complex water routing. In fact, in the laVerkin
Springs Unit, a portion of the downstream surface water disappears into a
ground-water reservoi r to reappear some years later at another 1 oc at i on.
The complexity of ground-water systems thus far encountered strongly
influences the design of ground-water wells and pumping fields. In some
cases, specially designed equipment will have to be used to remove dis-
solved gases and other constituents found in the saline ground-water
sources.

In order to deal with the complexity and unknowns of ground water, ongoing
construction activities scheduled for the Grand Valley and Paradox Valley
Units are being staged. Staged construction strategy allows separable fea-
tures of the control system to be bui lt and closely monitored to confirm
bas i c under standi n9s of the ground-water mechani sms i nvo 1 ved. Staged
operation also allows adequate measurement of the lag times and interaction
of the ground-water and surface-water systems. It is expected that in some
cases it may take months or even years for salt removal to be confirmed at
downstream salinity monitoring stations. large ground-water systems and
normal precipitation cycles may tend to temporarily "mask" man-related
attempts at salt removal.

Reclamation has embarked on a major analysis of long-term sal inity and
specifiC ion trends [2]. The analysis of trends contained in some 70 years
of water Quality records is possible with the extensive use of computers.
The ongo i ng stud i es are 1 arge 1 y d i recled to a better unders t and i n9 of the
relationships between land use, water use, hydrology, Chemical and bio-
logical mechanisms, and long-term salinity trends.

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