The present day Salton Sea is approximately 35 miles long and 15 miles wide, located in the lowest portion of the desert valley in Imperial and Riverside counties. The lake is a terminal waterbody (no water outflows) sustained primarily by agricultural return flow water from the Imperial, Coachella and Mexicali valleys. The lake is relatively shallow with water depths of 1 to 3 feet extending thousands of feet from the shoreline. The deepest areas in the lake are less than 50 feet deep and are located in the north and south central portions of the lake.
The Salton Sea is located in the southern Colorado Desert in an area known as the Salton Sink or Salton Trough. The trough is below sea level. The Salton Trough was once an extension of the Gulf of California and over millions of years the Colorado River deposited large amounts of silt into the area filling much of the current trough and forming a large river delta to the south of the present Salton Sea. In more recent geologic history, the Colorado River had a history of inundating the area during river flood events. These events resulted in periodic flooding of the basin and at times the Colorado River flowed into the valley and then back out the southern end of the trough to the ocean. Lake Cahuilla is the last evidence of large scale flooding of the valley. Remnants of the Cahuilla shoreline can be seen along the lower edges of the mountains in the northwestern corner of the valley. For over a thousand years the area was mostly dry, although occasional inflows did occur and portions of the sink area were periodically inundated or wet. There is some historical evidence to suggest that the area was at least partially flooded as recently as the 1600s. The construction of dams and reservoirs on the lower Colorado River now regulate the flows on the river, making another Lake Cahuilla a very unlikely prospect.
The existing lake was formed in 1905 when the Colorado River breached an irrigation inlet and flowed unchecked into the area. In the spring of 1907 the channel breach was finally closed leaving an approximately 316,000 acre lake that had a water elevation of approximately 197 feet below mean sea level. With the high evaporation rates in the area the lake shrank to approximately 165,000 acres by 1920 with an elevation of approximately 250 feet below mean sea level. As agricultural production increased in the Imperial and Coachella valleys the lake elevation rose to around 230 feet below mean sea level. In response to the increasing elevations IID built a series of retaining berms around the southern end of the lake to prevent additional flooding of adjacent farm land. In the early 2000s lake levels began to drop in response to lower inflows. In 2013 the approximate elevation of the lake was 231 feet below mean sea level and it encompassed approximately 222,000 acres.
Salton Sea Challenges
In the 1980s and 1990s inflows to the lake were approximately 1.2 to 1.3 million acre-feet per year, with the majority of the flow from agricultural return flows augmented with inflows from Mexico and other sources. As farmers become more efficient with the use of irrigation water, the return flows decreased as have inflows from Mexico. Current hydrologic projections suggest that after 2020, the lake will receive approximately 700,000 and 800,000 acre-feet of inflow annually. The result will be a lake that is approximately the same size as the lake in 1920 at 162,000 acres and an elevation of 254 feet below means seal level.
This means the exposure of upwards of 70,000 acres of previously inundated lake bed (playa) over the next 10 years. While the exact composition of the playa soils are unknown, current data suggests that the soils are highly saline and may contain constituents that could be toxic. The exposed playa will be a source of particulate matter that will become airborne in windy conditions and will further deteriorate the compromised air quality in the Imperial and Coachella valleys.
While the decreased elevation and exposed playa are a serious risk to human and wildlife health, the level of salinity in the lake is of more concern to maintaining the current wildlife ecosystem. As a terminal waterbody, the Salton Sea has no outlet to purge accumulated salts and nutrients, and over the years since its formation the water has become increasingly saline. Current salinity concentrations are significantly higher than ocean water. With reduced inflows caused by the water transfer the salinity concentration trend will increase; resulting in the acceleration of significant changes to the lake’s ecosystem.
The lake is also very high in nutrients. The high nutrient levels make for a very productive ecosystem, but also contribute to the deteriorate water quality of the lake. High nutrients contribute to large scale algae blooms, high biological oxygen demand and ultimately lead to lower levels of dissolved oxygen in the water column. Coupling these conditions with the increase in salinity poses a significant stress on the existing ecosystem. Several fish die offs and scattered avian mortality events have occurred at the lake. The fish population in the lake is primarily a Mozambique tilapia variant, a sub-tropical fresh water fish that is unlikely to survive the increasing salinity. With the projected decline in the fishery, so go the migratory and permanent pisivourous bird populations.
Despite the increasingly dire conditions at the lake, it remains one of the most important links on the Pacific Flyway, supporting over 400 species of birds and a myriad of invertebrates. The lake and the surrounding brackish to fresh water habitat also supports several federally or state listed endangered species, including the Ridgeway rail, the desert pupfish and the California black rail. With the loss of the majority of the aquatic habitat along this portion of the Pacific Flyway, preserving the lake is of critical importance.
For more information regarding: revitalization visit the Salton Sea Authority; or the Salton Basin and Colorado Delta you can visit the SDSU Center for Inland Waters website; or for travel and tourism information you can visit visitgreaterpalmsprings.com.