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o ~ ~ N comprehensive as possible and that it will result in maximum salinity reduction to the Colorado River. Reclamation believes that the lateral improvement program in the Grand Valley has many advantages for the water users. We encourage you to become informed about the program by attending one of the public meetings on October 22 and 23. Also plan to attend the public meet ing on November 19 to give us your input. THE SALINITY PROBLEM What Is The Salt Problem? The Colorado River Basin is composed of seven Western States: Colorado, Wyoming, Utah. New Mexi.:o, Nevada, Arizona, and Callfornia. At its headwaters in Colorado) the salinity concentration (or tota~ di~solved soLids) of the river is about 50 milligrams per liter (referred to as mg/L and a measure of water quality). As it flows more than 1,400 miles to its terminus in the Gulf of California, the river picks up salt contributions from a variety of manmade and natural sources. The average salinity level at Imperial Dam (the last major diversion point of the Colorado River in the U,S.) in 1985 was about 608 mg/L. In drier years, aVerage salinity levels have been as high as 896 mg/L (1970), Water with salinity concentrations of l,OOO mg/L or less is considered to be satisfactory for most crops. However, concentrations of 700 mg/L can have hamful effects on salt-sensitive crops. On land with good drainage, concentrations of more than l,OOO mg/L can be used for some crops, According to Environmental Protection Agency (EPA) standards, the salinity concentration of public drinking water should be less than 500 mg/L. What Harm Does Salinity Do? High salinity concentrations in the Lower Colorado River Basin affects more than 18 mi II ion peop I e and about 1 million acres of irrigated farmland in the United States--most severely affected in economic terms are the municipal and industrial water users. It is currently estimated that for every milligram-per-liter increase in salinity at Imperial Dam, there is a corresponding annual increase of $610,000 in economic losses which affect Lower Colorado River Basin water users. This does not include the damages also caused in Mexico. What Is Being Done About It? In 1972, an amendment to the Federal Water Pollution Control Act (Public Law 92-500, now known commonly as the Clean Water Act) was passed which had as its objective restoring and maintaining the integri ty of the Nat ion's waters. The EPA interprets this Act to require water quality standards. Standards for the Colorado River were set in 1972 and require the average salinity at Imperial Dam to be held below 879 mg/L. To meet the standards required by the Act, Reclamation and the Soil Conservation Service (SCS) are implementing projects to reduce the amount of salt entering and mixing with the Colorado River flow. How Can The Grand Valley Unit Help? A fully implemented lateral improvement program in the Grand Valley is expected to reduce the salt loading to the Colorado River by approximately 161,400 tons annually. This amounts to a reduction of about 15 mg/L at Imperial Dam.