FOR A WELCOMED CHANGE, some good news is being generated by the Sierra Nevada snowpack situation even as snow amounts and spring and summer runoff hopes continue to decrease. While snow surveyors this week were finding the white blanket atop the Kings River watershed in increasingly short supply, a state contract was awarded for much broader use of a vital advancement in measuring snowpack which supplies much of the San Joaquin Valley’s water.
This program is the Airborne Snow Observatory (ASO), an aerial snow monitoring tool that provides precise measurements of depth for every square foot of snow within the watershed. Combined with the conventional surveys, ASO provides a complete and near perfect picture of snow water content that is robust against climate change.
The first of this season’s ASO flights over a portion of the Kings River watershed took place Wednesday (March 2) and will be concluded as quickly as conditions permit. ASO-gathered data will be combined with this week’s March 1 on-the-ground snow surveys. Such surveys and automated snow sensor stations remain vital parts of the overall snowpack data collection process because of their measurements of snow water content equivalency.
This winter’s continued drought conditions unfortunately have continued to be reflected in the latest snow survey findings, the Kings River Water Association announced today.
The 23 remote Kings watershed courses measured showed average snowpack water content of 15.4 inches, 68% of the normal to date or 55% of April 1, the date upon which Sierra snow conditions typically peak. Snow depths are averaging 40.2 inches. KRWA and Pacific Gas and Electric Company staff took the surveys.
“Southern and eastern mountainsides looked melted out,” KRWA Assistant Watermaster Matt Meadows said. “That is an indication of less coverage than typical for this time of year despite the numbers indicated on the snow survey.”
ASO flights detect all bare spots while using LiDAR (light detection and ranging) technology to accurately measure all snow depths and, by detecting snow reflection, how much sunshine is being absorbed.
“ASO is an addition to our existing snow survey and snow sensor programs,” said Kings River Watermaster Steve Haugen. “What it does is greatly improve accuracy and our knowledge. This information gives water managers the most accurate data available to analyze how much water will reach Pine Flat Reservoir and when, allowing the optimization of the various demands for precious water supplies.”
Airborne snow depth measurement flights can cover the entire Kings River watershed with approximately 400 million measurements taken over a 10-hour period, completely and accurately assessing snow depth across all locations. LiDAR data collected from the flights over snow is of high resolution. It is compared with base data collected during the summer when no snow is present.
Funding for airborne LiDAR snowpack measurement flights, the tool with the highest accuracy, has been inconsistent. In water year 2020, funding was secured to conduct three airborne flights in the Kings River watershed. In water year 2021, funding was secured via the California Department of Water Resources to conduct only two flights. KRWA believes approximately 10 flights annually would provide the most complete data.
An updated runoff forecast from the California Department of Water Resources, based on the March 1 snow surveys, is expected to be issued on or about March 8. The most recent updated forecast, issued by the DWR on February 22, predicted that natural Kings River runoff (as if there were no dams) during the soon-to-begin April-through-July peak snowmelt season will be only 810,000 acre-feet, 67% of average.
Haugen said every water management decision made in California relies on accurate forecast information. “The better the initial information, the better the results, he said, adding the KRWA has supported and promoted the ASO program evolution to introduce new technology and techniques to strengthen the accuracy of snowpack analysis across California, including the Kings River watershed.
ASO technology was developed at the NASA Jet Propulsion Laboratory. LiDAR is similar to radar but relies on near-infrared light to measure the distance of objects. Because the measurements are being taken continuously overhead through a wide geographic area, ASO is like putting a snow depth sensor in every square foot of snow in the mountains.
“ASO provides invaluable information that is not otherwise available, most importantly information about the rate of melt that provides a real opportunity to optimize reservoir operations for water supply, flood control, and instream requirements,” Haugen said.
For More Information, Please Contact:
STEVE HAUGEN, Kings River Watermaster, (559) 266-0767 RANDY McFARLAND, (559) 260-2775