Congressional concern for securing funding and developing plans to restore the Salton Sea stems from the value of the Sea as a habitat for federal and state listed endangered species as well as other migrating and resident bird species, a reservoir for agricultural drainage, a center for recreation, and a wetland ecosystem. The Salton Sea is located in southern California and is considered the largest inland water body in the state ( Figure 1 ). The Salton Sea was formed in 1905 when a levee break allowed water to flow into the Salton Basin from the Colorado River uninterrupted for 18 months. The Salton Sea was not the first body of water in the basin; several other lakes have existed in the Basin throughout its geological history. Interest in the ecological health of the Salton Sea has amplified since 2002, when negotiations of proposed water transfers in southern California began. The proposed water transfers would have diverted agricultural water from farms in the Imperial Valley to San Diego and the Coachella Valley. This was expected to result in less water flowing into the Salton Sea, which some scientists predict would have increased the rate of evaporation in the Sea so that salinity levels would be lethal to most fish and wildlife in less than 10 years. Questions over how environmental impacts in the Salton Sea would be mitigated and who ultimately would be responsible for their costs played a large part in the negotiations. On September 12, 2003, the State of California enacted three bills that contain provisions that would allocate an estimated $300 million for restoring the Salton Sea. These funds were secured when the Quantification Settlement Agreement (QSA) was passed on October 10, 2003. The agreement allows California to gradually reduce its over-dependence on the Colorado River to 4.4 million acre-feet in the absence of surplus water through voluntary agriculture-to-urban water transfers and other water supply programs. The agreement will attempt to protect inflows to the Salton Sea for 15 years and establish a restoration fund for the Sea. The fund will receive money from mitigation fees collected from the sale of water transfers in the region. These acts also authorize the creation of an advisory committee for restoration activities and set a deadline of 2006 for the California State Resources Agency to prepare a restoration study of the Salton Sea. The Salton Basin, where the Salton Sea is located, has supported many lakes and water bodies throughout its geological history. The last of these prehistoric water bodies was Lake Cahuilla, which dried up nearly 400 years ago. In 1901, a portion of the Colorado River was diverted through the Imperial canal to irrigate agricultural fields in the Salton Basin. Water flowed through the New Alamo River and into the Imperial Valley from this channel. In 1905, water from spring floods broke through a levee diverting a portion of the Colorado River, and began forming the Salton Sea. Water flowed uninterrupted for nearly 18 months into the Salton Sea before it could be turned back to the Gulf of California. The Sea formed as a closed basin with no outlets. (This is still valid today.) The Sea consisted largely of fresh water at its inception, and immediately began to evaporate and increase in salinity. Due to the construction of the Hoover Dam and the All American Canal in 1928, some water from the Colorado River was directly transferred to the Imperial Valley for irrigation. After flowing through agricultural lands, this water entered the Salton Sea and prevented it from completely evaporating. In 1924 and 1928, President Coolidge executed Public Water Reserve Orders 90 and 114 for the withdrawal of lands located in and around the Salton Sea. These lands were designated as a repository for agricultural, subsurface, and surface water drainage. During this period, dissolved salts in the Colorado River water, combined with evaporation, led to an increasingly saline Sea and subsequent population reductions in freshwater fish species. In 1950, when the salinity of the Sea was roughly equivalent to the ocean, the California Department of Resources began transferring saltwater fish species to the Sea. Some species thrived in the Sea, including the orangemouth corvina ( Cynoscion xanthulus ) and gulf croaker ( Bairdiella icistia ). During this period, and in the next two decades, the Sea became a popular destination for sportfishing and tourism. However, changes to the Sea including the inundation of resort areas and wildlife habitats, bird and fish die-offs, and health threats of untreated water, among other things, led to a decline in recreation and development around the Sea in the 1960s. Health advisories, for example, included posted warnings against human contact with the Sea and consuming fish from the Sea. The stench of dead fish and concern over inorganic and organic pollution from the Sea were also factors that led to less interest in inhabiting the shorelines of the Sea. In the mid-1980s, recreation around the Sea had dropped nearly 50% since the 1960s. In the past few decades the focus of activities concerning the Sea has been on the environmental problems it faces. The current Salton Sea ecosystem has problems ranging from poor water quality to loss of habitat. The New River provides water to the Salton Sea after it flows through the urban area of Mexicali, Mexico and the Imperial Valley. As the urban area of Mexicali increased, water pollution from sewage treatment plants, agricultural runoff, and other sources of pollution has increased. Water inflows to the Sea from another country illustrate the complexity of efforts to regulate water pollution in the Sea. Elevated levels of selenium and DDE have been detected in Sea fish and wildlife. Selenium can cause a variety of physical problems in humans and was one of the reasons for advisories against consuming too much fish from the Sea. DDE, which is derived from DDT, is also found in waters of the Sea. DDT was banned in the United States in 1972, but is still used in Mexico as an insecticide. Both DDE and selenium cause reproductive problems in fish and birds. The Salton Sea provides a variety of habitat for fish and wildlife species, including open water, estuaries, salt marshes, and riparian corridors. Due to the loss of wetland habitat in southern California and throughout the state's vast Central Valley, the Salton Sea is regarded as a primary stopover point for birds on the Pacific Flyway. The Salton Sea is periodically inhabited during the year by the second largest number of bird species in the United States, including some federal and state recognized threatened and endangered species. In one season, for example, more than 380 bird species were observed. Surveys have estimated that the total population of birds in the Salton Sea can reach up to 500,000 birds per month. The Sea also provides habitat for a large fish population, most of which were originally introduced manually or through drainage ditches leading to the Sea. The most ubiquitous species in the Salton Sea is the tilapia ( Oreochromis mossambicus ), which was introduced by farmers to control weeds in their ponds. The ecosystem properties of the Salton Sea are largely determined by its water level, chemical and salt concentration, and balance between the rate of evaporation and water inflow. Nearly 75% of the water flowing into the Sea comes from agricultural run-off originating in the Imperial and Coachella Valleys in California, the other 25% is from rain and other surface inflows. The salinity of the Sea has been increasing over time. Recent studies have reported that about 4 million tons of salt enter the Sea annually. As water evaporates, the concentration of salt increases. Presently, the salinity level in the Sea is approximately 44 parts per thousand (ppt), which is approximately 25% greater than ocean water and one-sixth that of the Great Salt Lake, Utah (280 ppt). High salinity levels combined with high concentrations of other toxic substances (e.g., naturally occurring selenium) and disease is thought to be a factor in the mortality of fish and birds in the Sea. Large-scale mortality of fish and birds in and around the Salton Sea received national attention in the 1990s. In 1992, for example, nearly 150,000 eared grebes ( Podiceps nigricollis ) died in the Sea. Some scientists proposed that grebes may have died from consuming fish with high selenium levels; whereas other scientists attribute grebe mortality to disease. Definitive answers to these deaths were not found. In 1994, another 20,000 eared grebes died, and in 1996, approximately 20,000 American white pelicans ( Pelecanus erythroryhnchos ) and brown pelicans ( Pelecanus occidentalis ) died in and around the Sea. The death of brown pelicans was especially dramatic since it is a federally listed endangered species (listed in 1970). Indeed, avian mortality was reported to be highest in and around the Sea in the 1990s compared to other decades. The cause of mortality in these events was largely attributed to microbes that lead to disease in birds. The origin of these microbes was unclear, although some scientists have attributed them to contaminated fish that were eaten by birds. Large fish kills are also reported in the Sea, including the mass mortality of tilapia and gulf croakers ( Bairdiella icistia ). Dead fish were thought to have weakened immunity because of high levels of toxins (e.g., selenium and DDE) and parasites, and low levels of dissolved oxygen in the Sea. Low immunity in fish will increase their chances of contracting disease and dying. High salinity levels are also thought to affect fish populations in the Sea. Scientists regard salinity levels of 33 - 37 ppt adequate for ocean living organisms. Beyond salinity levels of 40 ppt, fish may have limited reproductive success and physiological stress. The mortality of bird and fish species in and around the Salton Sea is of concern because of federal and state listed endangered species that inhabit the Sea.