7905

• UCREFRP Catalog Number: 7905
• Author: U.S. Department of the Interior.
• Title: Quality of Water, Colorado River Basin.
• USFW Year: 1995.
• USFW - Doc Type: Progress Report No. 17,
• Copyright Material: NO

The soluble mineral content of saline formations is variable and can be significantly
different within one stratigraphic unit. The determination of the soluble mineral
content of surficial soils is highly dependent upon the sampling and analytical
methods used. The effects of contact time and sediment to water ratios on rate and
extent of dissolution are extremely important. Since much of the salt is dependent
upon sediment load, contact time and sediment to water ratio must be considered.
Laronne[15] recommends a sediment to water ratio of 1 percent. This ratio allows for
greater dissolution of salts and a better estimate of salinity contributed from erosion.

EFFECTS OF WATER QUALITY ON WATER USERS

Economic

Estimating Economic Impacts of Salinity of the Colorado Riuer[161 updated the
economic impacts of salinity in the Colorado River Basin and developed a method of
forecasting economic impacts as
salinity levels rise and water use
changes in the future. The first
objective of the study was to update,
revise, clarify, and refine the estimates
of economic damages from salinity that
had been described in earlier
studies[17,18]. Figure 4 shows the
relative impact of salinity on water
users in the Lower Colorado River
Basin. The study estimated damages
were $311 million per year based on
1976-85 salinity levels in the Lower
Basin and 1986 dollar values. During
this period, salinity averaged 767 mg/L
at Imperial Dam.

Crop (36%)

Management (11 %)

Household (50%)

Figure 4.-Salinity costs by user group.

The second objective of the study was to provide a better means of estimating present
and future salinity damages through the development of a comprehensive computer
program. Damages for 1976-85 were estimated by the study to be $311 million per
year, but as salinity levels increase to more normal levels, damages (figure 5) will also
increase. Sensitivity analysis[191 using the damage model showed that damages (or
the value of salinity control) increase with salinity.

In 1993, the salinity at Imperial Dam was 784 mg/L. Figure 5 shows that at this level
of salinity, damages exceed $500 million per year. As salinity approaches the salinity
standards (879 mg/L at Imperial Dam), damages are projected to exceed $1 billion per
year. Using a relatively conservative analysis, the benefit of salinity control was
estimated to be $340 per ton (1994 dollar values). In comparison, the cost of salinity
control generally ranges from $20 to $100 per ton.

14

j