The Salton Sea is located in southern California and is considered the largest inland water body in the state. The Salton Sea was formed in 1905 when the Colorado River broke through a canal gate, allowing water to flow into the Salton Basin uninterrupted for 18 months. Since its formation, the Sea has been maintained largely through agricultural runoff from surrounding areas. 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. The creation of the Salton Sea in 1905 eventually led to development of its shoreline and its waters were stocked with sportfish. Until the late 1960s, the Salton Sea was one of the most prolific sport fisheries in the country, with a high diversity of birds and wildlife. The Salton Sea also serves as an important wetland area along the Pacific Flyway, a migratory route for birds stretching from Alaska to Patagonia. The ecology and economy surrounding the Salton Sea has deteriorated steadily over the past several decades due, in part, to a changing ecosystem marked by decreasing water flows and increasing salinity. The Salton Sea has shrunk due to evaporation and declining water inflows, resulting in increased salinity and deteriorating fish and wildlife habitat. High salinity levels combined with toxic concentrations of substances have led to disease and widespread mortality of fish and birds. Current saline levels are nearing fatal levels for all fish, leading some scientists to predict that fatal saline levels will occur by 2018. The subsequent population decline of fish could have severe effects on migratory birds that use the Salton Sea as a primary stopover point on the Pacific Flyway. Furthermore, exposed lake beds could allow toxins and dust to enter the air, which could lead to air pollution and human health problems. Attention to the ecological condition of the Salton Sea and efforts to restore the Sea have existed for several decades. However, interest in the ecological health of the Salton Sea has amplified since 2003, when the Quantification Settlement Agreement (QSA) was signed by several water districts in California, the state of California, and the Department of the Interior (DOI), and signed into California law. QSA requires California to gradually reduce its consumption of Colorado River water to 4.4 million acre-feet a year (AFY) through voluntary agriculture-to-urban water transfers and other water efficiency measures. The implementation of this agreement has resulted in less water flowing into the Salton Sea, thus accelerating its ecological decline. However, as part of the QSA, participating water districts agreed to contribute $163 million toward mitigation and restoration. In addition, the water districts agreed to provide 200,000 AFY of Colorado River water to the Sea though December 31, 2017. While some of these mitigation efforts have been implemented, longer-term restoration efforts and the distribution of these costs are still contested and uncertain. Congressional concern for restoring the Salton Sea stems, in part, from the value of the Sea as habitat for federal and state listed endangered species, as well as other migrating and resident bird species; a reservoir for agricultural drainage waters; a center for recreation; and a large wetland ecosystem, among other things. Concerns over air pollution from exposed sea beds have also been expressed by Members of Congress. These concerns have been reflected, in part, by efforts to address the restoration of the Salton Sea and its ecosystem. Congress has passed laws addressing the restoration of the Salton Sea and authorized funds for restoring the Salton Sea in the Water Resources Development Act of 2007. Current restoration efforts have been led mainly by the state and local governments. Consensus around restoring the Salton Sea has not been fully attained. Some contend that the Salton Sea should not be restored. They argue that the geological history of the Salton Sea demonstrates a pattern of water bodies naturally shrinking and disappearing, and then reforming over time. They note that the Salton Sea will follow a similar process and that countering this natural process will be costly and ultimately not worth the cost. These opponents argue that the restoration funds should instead be used to restore other natural wetlands in California, such as the Sacramento and San Joaquin rivers' delta confluence with San Francisco Bay (Bay-Delta). To counter this argument, some respond by noting that the natural inflows of water into the Salton Sea have been artificially diverted by humans when the Colorado River was diverted into a canal and that natural processes and cycles will not exist again with these structures in place. Further, they note that the value of restoring the Salton Sea lies in its ecological significance as a large wetland along the Pacific Flyway and a habitat for fish and wildlife, and its potential to stimulate economic development in the region through tourism, recreation, and energy development. The Salton Sea is located in southern California and is considered the largest inland water body in the state. 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 canal head-gate diverting a portion of the Colorado River into the Basin and forming the Salton Sea. Water flowed uninterrupted for nearly 18 months into the Salton Sea before it could be redirected to the Gulf of California. The new Sea formed as a closed basin with no outlets, which is still its condition today. The Sea consisted largely of fresh water at its inception; however, the water immediately began to evaporate and increase in salinity. The construction of Hoover Dam and the All American Canal in 1928 allowed water from the Colorado River to be transferred directly to the Imperial Valley for irrigation. After flowing through agricultural lands, this water drained into the Salton Sea, thereby preventing the Sea from 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. 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 runoff originating in the Imperial and Coachella valleys in California, the other 25% is from rain and other surface inflows. As water in the Sea evaporates, the concentration of salt increases. Presently, the salinity level in the Sea is approximately 52 parts per thousand (ppt), which is approximately 50% greater than ocean water and one-fifth that of the Great Salt Lake in Utah (270 ppt) (See Figure 2 ). At 52 ppt, the Salton Sea is considered to be hypersaline. High salinity combines with extreme eutrophication to cause fish kills in the Sea. Eutrophication can result in anoxic conditions leading to fish death. In 1950, the Sea reached salinity levels similar to the Pacific Ocean. At this time, the California Department of Fish and Game began transferring saltwater fish species to the Sea. During the 1950s, and in the next two decades, the Sea became a popular destination for sport fishing and tourism. However, changes to the Sea, including flooding of resort areas and wildlife habitat, bird and fish die-offs, and health threats of untreated water, led to a decline in recreation and development around the Sea in the 1960s. The current salinity levels in the Sea are too high to support the former diversity of fish. The most ubiquitous species in the Salton Sea now is the tilapia ( Oreochromis mossambicus ), which was introduced by farmers to control weeds in their ponds in 1964. In addition, the Sea also houses the endangered desert pupfish ( Cyprinodon macularius ), the only native fish species in the Sea. Deteriorating water quality has also had a large detrimental impact on the invertebrate life in the Sea, such as on pileworms and barnacles, two important components of the Salton Sea food web. Currently, few fish can survive in the hypersaline waters of the Sea. Future salinity predictions indicate that all species of fish may disappear from the Sea as early as 2023. The Salton Sea ecosystem 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 a primary stopover point for birds on the Pacific Flyway. The Sea supports more than 400 species of resident and migratory birds, of which more than 50 are species of special status (including three listed under the Endangered Species Act (ESA)). Surveys have estimated that the total population of birds in the Salton Sea can reach up to 500,000 birds per month. Many of these birds are piscivorous, relying on fish in the Salton Sea for sustenance. Other birds can feed on both the fish and invertebrates found in the basin. 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. For example, the Yuma clapper rail ( Rallus longirostris yumanensis ) is a federally listed endangered species, residing in and around the Sea during the year.