In the last 25 years, the Salton Sea, California’s most polluted inland lake, has lost one-third of its water. According to new research, the reason for the shrinking is a decrease in Colorado River flow.
The concentration of salt and chemicals in the remaining water has increased dramatically as the lake dries up, causing a mass die-off of fish and birds, including endangered species. The salty, toxic water that coats the dry lakebed turns it into dust, causing respiratory problems for nearby residents.
“It’s an environmental disaster,” said Juan S. Acero Triana, a UCR hydrologist and lead author of a new study on water movement on and beneath the Earth’s surface near the Salton Sea.
There have been numerous hypotheses proposed as to why water levels are steadily declining. Some attribute the lake’s drying to climate change and heat. Others believe agriculture may be to blame. As irrigation systems improve and crops are modified to use less water, less water enters the Salton Sea. However, according to the researchers, these are not the primary causes of the sea’s decline.
Typically, the Sea is regarded as an independent system, and a watershed-centric approach that takes into account surface and groundwater resources is required to find a solution. As the environmental risks of a shrinking Sea increase, all parties must collaborate to mitigate the risk.Hoori Ajami
“There is less water flowing into the Sea from the Colorado River, and that is what is causing the problem,” said Hoori Ajami, a UCR hydrologist and study co-author and principal investigator. This discovery, as well as the methods used to obtain it, has been published in the journal Water Resources Research.
The researchers considered all major processes impacting the water balance of an endorheic lake like the Salton Sea, where water flows in but not out to any tributaries. Endorheic lakes worldwide have been shrinking in recent decades at what the researchers call an “alarming” rate due to the combined effects of global warming and diversion of water for agricultural and industrial purposes.
To understand the reasons for the Salton Sea’s decline, the researchers used a hydrologic model that accounted for all processes in the surrounding areas that impact the lake’s water balance, including climate, soil types, land slope, and plant growth.
Geographically the model included data not only about the Sea itself, but also from the surrounding watershed, streams entering the lake, and the land area that drains into those streams.
Data for the model was hard to come by as this is a transboundary basin on the US-Mexico border between California and Baja California Norte, and stakeholders may have been reluctant to share data that could alter previously earned water rights. However, using publicly available data and data mining techniques, UCR researchers were able to simulate long-term water balance dynamics and identify reduced Colorado River flows as the main cause of the Salton Sea shrinking.
“It’s not entirely clear, however, whether the decline in Colorado River water is more due to global warming drying out the river, or reductions in allocation levels to California, or both,” Acero Triana said.
Despite the ambiguity, the researchers believe the study should send a message to water management agencies and legislators that the Salton Sea watershed should be considered part of the Colorado River basin.
“Typically, the Sea is regarded as an independent system, and a watershed-centric approach that takes into account surface and groundwater resources is required to find a solution,” Ajami explained. “As the environmental risks of a shrinking Sea increase, all parties must collaborate to mitigate the risk.”