Demand for snow runoff forecasting is surging in the San Joaquin Valley, particularly after the past bone-dry year. Snow monitoring flights are already being tentatively scheduled by valley water districts ahead of winter.
“Everybody’s anxious for the water year,” said Michael Anderson, state climatologist for California’s Department of Water Resources (DWR). “What is it going to bring?”
One of the newer and more effective ways of monitoring is by flying imaging technology over watersheds to see and analyze snowpack. Airborne Snow Observatories (ASO) is the company behind this method. Forecasting can help water managers better prepare and know how to best deliver water. It can also help with flood risk planning.
DWR has been partnered with ASO since 2013 and is now looking to expand that partnership into more watersheds. So far, the western slopes of the Sierra Nevadas in the Kaweah basin area have been one of the main areas for monitoring. But the state is looking to make ASO part of its infrastructure throughout California.
ASO started as a research project with NASA’s Jet Propulsion Laboratory. In 2019, it split from NASA and became its own company. Now, it partners with state, federal and local entities to monitor and forecast snowpack runoff in California, other western states and areas around the globe.
ASO flies planes equipped with Lidar laser scanners and imaging spectrometers. The Lidar scanners shoot 400,000 lasers per second and measure the distance to the ground which gives elevation data. And the imaging spectrometer gets surface properties of the snow.
When combined, the surveys can gather highly detailed and accurate data about entire watersheds, including snow reflectivity, snow depth, density and water equivalent.
“It’s really a game changer,” said Jeff Deems, co-founder of ASO.
Most water managers are currently hedging against worst case scenarios and are being conservative in water use, said Deems. And the demand for ASO is growing.
“I don’t even have to anticipate, we’re seeing it,” said Deems. “The drumbeat for ASO has been steadily growing louder over the years.”
Without good snowpack data, it’s difficult to know the magnitude and timing of runoff, said Deems.
And on-the-ground manual snow monitoring is becoming less accurate, added the state’s Anderson. On the ground measurements rely on comparisons to historical data. Those methods aren’t as detailed or comprehensive and as the climate continues to warm they aren’t performing as well as they used to, he said.
“Personally, I underestimated the value of ASO in a drought year,” said Chad Moore, restoration flow coordinator for the San Joaquin River Restoration Program. “But having gone through the 2021 water year, I can attest it’s really just as important to have this information in a dry year.”
The restoration program is part of the Bureau of Reclamation and is responsible for the reintroduction of spring-run Chinook salmon into the San Joaquin River, a native species that disappeared from the river after the construction of the Friant Dam dried up most of the river.
Runoff forecasting is especially important for the restoration program. Farmers don’t want too much water released for fish and environmentalists don’t want too little. So knowing what reservoir inflows will be like is critical and can also help the program better use water for flood releases and groundwater recharge.
But understanding runoff in extremely dry years can be more difficult. In wet years, the ground is saturated and most snow melt runs off. But in dry years, parched ground can absorb runoff which makes it challenging to know how much there will be. That’s what happened this past year, as SJV Water reported. What little snow there was at the end of winter was mostly gone by springtime. And ASO flights discovered very little snow even at higher elevations.
The San Joaquin River Restoration Program has contracts with ASO in place already but when the flights will start depends on how wet the winter months are. They could start flying as early as January if it’s a wet season and as late as March if not.