Runoff and flood diversions are helping the Great Salt Lake be slightly less salty
Runoff season has been good news for the Great Salt Lake. After hitting a record low in November, water levels are up a few feet. On top of that, the Weber Basin Water Conservancy District is releasing 650 million gallons of water every day from Willard Bay Reservoir into the lake.
The district’s effort is to mitigate runoff flood concerns after Utah's record snowfall. Still, the injection of water is changing the lake’s salinity levels, supporting the health and ecosystem of the lake.
Along with water levels, salinity is another of the Great Salt Lake’s vital signs.
“We’re kind of killing, you know, two birds with one stone,” said Darren Hess, assistant general manager at Weber Basin Water Conservancy District.
Hess said the district nearly emptied its seven reservoirs to prepare for the spring runoff. The Weber Riverhas seen frequent flood warnings and the South Fork of the Ogden River is overflowing; high water there recently washed away part of the bank underneath State Route 39 in Ogden Canyon.
To prevent more flooding, water is being diverted to Willard Bay from the main stem of the Weber River using the Slaterville Diversion Dam in Weber County. But Scott Paxman, general manager and CEO of Weber Basin Water Conservancy District, said Willard Bay is already close to 90% full, so they are releasing 1,000 cubic feet per second of water to the south arm of the Great Salt Lake.
In addition to water from the Weber River and Willard Bay, the Central Utah Water Conservancy District is also diverting 50 million gallons of water each day to the Great Salt Lake. All this water has been improving the salinity.
Ben Stireman, the sovereign lands program administrator for the Utah Division of Forestry, Fire, and State Lands, said a healthy salinity level is 120-160 grams of salt per liter of water in the fall. When the salinity is in this range, brine shrimp and brine flies thrive and are able to reproduce so birds and other mammals can get enough food, and the ecosystem stays balanced. In the spring, the salinity should be lower to prepare for evaporation over the summer.
Marcelle Shoop, director of the Saline Lakes Program for the National Audubon Society, said proper water supports tens of thousands of waterbirds that rely on the lake. One of the prime bird habitats, Willard Spur, is between Bear River Bay and Willard Bay.
“These freshwater flows that are coming into Willard Spur are really important to freshen the water quality in the spur, and that helps to create, you know, the right kind of vegetation and bugs for many of the migratory waterbirds,” she said.
The salinity level at the time of the lake’s historic low was about 185 g/L, which meant life within the lake was at risk of dying off. With the record amount of snowpack and subsequent spring runoff, salinity has dropped to around 140-145 g/L.
Still, Stireman said it’s hard to predict if the salinity level will be in a healthy range by the end of the year, partly because of the causeway that separates the north and south arms of the Great Salt Lake. The breach and berm separating the arms, which can slow or stop water flow between the arms, was raised in February to an elevation of 4,192. As of a few weeks ago, water was spilling over the top of the berm, bringing new water to the saltier north arm of the lake.
The lake is expected to rise two or three more feet by the time the spring runoff has ended. With that Stireman said there could be another 15 or 20 g/L drop in salinity, but it all depends on how much water gets to the lake. The ideal elevation of water in the lake is around 4,200 feet, but even with the record-breaking amount of snow this year, Stireman said it likely won’t reach that mark.
“We probably need several years of good precipitation to get the lake to a level that we feel really comfortable with,” Stireman said.
Paxman also emphasized this point, saying Utahns still need to focus on watering efficiently and conserving water for future years.
“Conservation is more of a lifestyle change that we have to have regardless of the weather, regardless of if it’s a drought year or a good water year,” Paxman said. “We have to maintain that conservation ethic all the time.”