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Salton Sea 1995 Hydrographic GPS Survey

Introduction

The present water body of the Salton Sea, produced by an error of man, occupies parts of Imperial and Riverside Counties in California. The Salton Sea Basin (Basin), a below sea level topographic depression, extends north to Palm Springs, California, and south to the Gulf of California (fig 1). In the geologic past, the depression was part of the Gulf of California and underwent historic cycles of filling with water and emptying because of the radical course changes of the Colorado River. The last natural filling, dated 300 to 500 years ago, to a surface elevation slightly above sea level, formed what was then called Lake Cahuilla.

For many years, the depression was a dry lake bed until irrigation water was diverted to the Imperial Valley in 1901 from the Colorado River near Yuma, Arizona. The current body of water was formed during a 16-month period during 1905 to 1907, when the Colorado River breached a temporary man-made diversion facility and discharged into the Basin. The water filled the Basin to a maximum elevation of 195.9 feet below sea level before it was diverted back into its original channel. The maximum depth of water was about 76 feet, and the water boundaries extended 45 miles in length and 25 miles in width.

Today, the Salton Sea is the largest body of water in California. It is about 35 miles long, 15 miles wide at its widest point, and has maximum depths of about 51 feet at water surface elevation 227 feet below sea level. The primary use of the Sea is to serve as a repository for storage of agricultural drainage from the Imperial Valley to the south and Coachella Valley to the north. The drainage area of the Basin is about 8,360 square miles, but the greatest inflow is produced by agricultural drainage. For many years, a near balance of inflow and evaporation effectively stabilized the Sea's water surface elevation. With the Sea no longer increasing in volume to dilute the continuous inflow of salt, its salinity increased to a current concentration of about 44,000 milligrams per liter. As the Sea has become more saline, many of the fish and wildlife, recreation, aesthetic, and economic benefits of the Sea have been reduced or threatened.

Recently, an imbalance between inflows and evaporation has caused rising water levels that have adversely affected public and private property. The flood water damage caused by the rise of the Sea, although countered by numerous constructed dikes, has resulted in multi-million-dollar law suits. The rise of the Salton Sea because of inflow increases has slightly diluted the salinity level.

The Bureau of Reclamation (Reclamation) is participating in studies with the State of California and the Salton Sea Authority, whose members include the Coachella Valley Irrigation District, the Imperial Irrigation District, Imperial County, and Riverside County. The studies include methods to manage the salinity and water surface elevation of the Sea. Many of the proposals being considered for stabilizing and reducing salinity involve construction of facilities in the Sea such as dikes and intake structures. The analysis, design, and cost estimates of these and other proposals depend upon a knowledge of the bottom elevation contours and the water capacity, thus the purpose of this study.

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