Friday, 25 March 2016

The Salton Sea, California

The Salton Sea is a shallow, saline, endorheic rift lake located directly on the San Andreas Fault, predominantly in California's Imperial and Coachella valleys. 

The lake occupies the lowest elevations of the Salton Sink in the Colorado Desert of Imperial and Riverside counties in Southern California. Its surface is 234.0 ft below sea level. The deepest point of the sea is 5 ft higher than the lowest point of Death Valley. The sea is fed by the New, Whitewater, and Alamo rivers, as well as agricultural runoff, drainage systems, and creeks. 

Over millions of years the Colorado River has flowed into the Imperial Valley and deposited soil (creating fertile farmland) and building up the terrain constantly changing the course of the river. For the next thousands of years the river has flowed into and out of the valley alternately creating a freshwater lake, an increasingly saline lake, and a dry desert basin, depending on river flows and the balance between inflow and evaporative loss. The cycle of filling has been about every 400–500 years and has repeated itself many times. The latest natural cycle occurred around 1600-1700 as remembered by Native Americans who talked with the first settlers. Fish traps still exist at many locations and it is evident that the Native Americans would move the traps depending upon the cycle. 

The most recent inflow of water from the now heavily controlled Colorado River was accidentally created by the engineers of the California Development Company in 1905. In an effort to increase water flow into the area for farming, irrigation canals were dug from the Colorado River into the valley. Due to fears of silt buildup, a cut was made in the bank of the Colorado River to further increase the water flow. The resulting outflow overwhelmed the engineered canal, and the river flowed into the Salton Basin for two years, filling the historic dry lake bed and creating the modern sea, before repairs were completed. While it varies in dimensions and area with fluctuations in agricultural runoff and rainfall, the Salton Sea averages 15 miles (24 km) by 35 miles (56 km). With an estimated surface area of 350 square miles (910 km2), the Salton Sea is the largest lake in California. The average annual inflow is less than 1,200,000 acre feet (1.5 km3), which is enough to maintain a maximum depth of 44 feet (13 m) and a total volume of about 6,000,000 acre feet (7.4 km3). However, due to changes in water apportionments agreed upon for the Colorado River under the Quantification Settlement Agreement of 2003, the overall water level of the Sea is expected to decrease significantly between 2013 and 2021. 

The lake's salinity, about 44 grams per litre (0.0016 lb/cu in), is greater than that of the waters of the Pacific Ocean (35 g/L (0.0013 lb/cu in)), but less than that of the Great Salt Lake (which ranges from 50 to 70 g/L (0.0018 to 0.0025 lb/cu in)). The concentration grows at a rate of about one percent per year. About 4,000,000 short tons (3.6×109 kg) of salt is deposited in the valley each year.

Friday, 25 March 2016