WSP08768

• File Number: 8273.500
• Description: Colorado River Basin Salinity Control - Federal Agency Reports - EPA
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 7/1/1978
• Title: Implementation of Agricultural Salinity Control Technology in Grand Valley
• Water Supply Pro - Doc Type: Report/Study

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SECTION 1

INTRODUCTION

BACKGROUND

Approximately lO million metric tons (ll million tons) of
salts are delivered each year in the water supply serving the
Lower Colorado River Basin (Figure l). These salts reach Hoover
Dam in about l.36 million hectare-meters (ll million acre-feet)
of water. Studies have indicated that roughly 37 percent of
this salt load is to be contributed by irrigated agriculture in
the Upper Colorado River Basin (Figure 2). Present salinity
concentrations necessitate treatment of water for both municipal
and industrial uses throughout the Lower Basin. In fact,
concentrations at times approach the tolerance of many high-
value crops such as citrus, thus requiring the use of excessive
quantities of water for leaching and expensive water management
programs.

This situation is expected to become even more serious,
especially as many planned upstream water development projects
are constructed. Thus, a program for reduction of mineral
pollution is urgently needed in order to protect existing water
users from quality degradation during low flow periods and to
prevent the serious restriction of future basinwide economic
development. Due to the relatively large salinity contribution
from agriculture, it is obviously one sector in which to begin
implementation of technologies which will reduce the salt
loading from these areas.

The Grand Valley of Colorado is the largest contributor of
salts per hectare of irrigated land in the Upper Colorado River
Basin. Therefore, it was a 10gical place to begin investigating
salinity control alternatives. Water entering the near-surface
aquifers in the Grand Valley displaces highly mineralized water
into the Colorado River. In any area where the water is in
prolonged contact with soil, the mineral concentration of salts
will tend towards chemical equilibrium with the soil. In the
Grand Valley, high equilibrium salinity concentrations are known
to exist in the near-surface aquifer. The key to achieving a
reduction in salt loading is to reduce the groundwater inflows,
which will result in less displacement of water from the aquifer
into the river. In the Grand Valley, the main sources of ground-
water flows are conveyance seepage and deep percolation from

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