With curiosity, perseverance and innovation, James E. Church, Ph.D., launched snow surveying in the Tahoe Sierra; his methodology was later adopted by water agencies all over the American West and, in fact, around the world.
The importance of snow in the nation’s hydrologic systems cannot be overstated. In the western United States, 85 percent of freshwater runoff originates as snowmelt.
Over years of trial and error, first Church and then state and federal agency workers learned how to effectively obtain core samples from mountain snowpacks. The measurement of the snow-water equivalent provides vital information for predicting the volume of spring snowmelt and water runoff from elevated mountain terrain during the West’s dry seasons. Stored in an elaborate array of connected reservoirs, water is allocated for urban use, ranching, agriculture, fisheries and more.
Honoring James Church
A plaque dedicated to James Church is located just east of the Mount Rose summit
highway parking lot on the other side of the highway looking east into
Nevada with Mount Rose to the left.
Managing water levels in massive reservoirs is a complicated business. Especially in California where atmospheric rivers can overwhelm flood control systems, while severe drought can make storage goals impossible. In the 1960s and 70s, Western water managers would consider their work successful if they hit a reservoir storage level within 15 feet of their target. Today, as the science of snow surveying has advanced, it’s usually a matter of inches. Lake Tahoe is a reservoir managed for Truckee Meadows Water Authority in western Nevada. Tahoe’s springtime water-level rise is usually controlled and accurately predicted to within an inch or less.
Read Part I
When Church started his research in the early 1900s, he established the first snow course at Tahoe City meadows – now Tahoe City Golf Course. A snow course is a permanent line of set measurement probe sites that indicate the average SWE for a section of watershed. It’s more accurate than a solitary sample in a random location. Church was focused on Lake Tahoe and its flow into the Truckee River because his initial goal was to protect Reno, Nev., from catastrophic floods.
The Truckee River is one of the most volatile in the United States, averaging a damaging flood every nine years. In the 1930s, snow surveys were expanded throughout the Sierra Range, the Great Basin, Rocky Mountains and Pacific Northwest. The importance of snow in the nation’s hydrologic systems cannot be overstated. In the Western United States, 85 percent of freshwater runoff originates as snowmelt. East of the Rockies, nine of the most significant floods in the 20thCentury were directly related to snowmelt.
After World War II, the importance of streamflow management increased as California water agencies struggled to supply the state’s expanding agricultural industry, as well as its urban regions exploding with post-war population growth. Hydrologists still use the old-fashioned, monthly snow surveys developed by Church to measure water content — there are 1,100 manual checkpoints across the West — but this critical science has advanced dramatically in the past 50 years.
Manual sampling of snow is expensive, time-consuming and potentially dangerous for field crews. The process also degrades the snowpack, impacting the accuracy of subsequent sampling. Ironically, on the day that the surveyors go out to sample the snowpack with the Church-designed equipment, anyone with a computer can observe real-time snow-water equivalent amounts for any watershed in the West, based on remote sensor data that is constantly being uploaded to the Western Regional Climate Center in Reno.
Remarkably, the first remote data streaming of snow-water equivalent began at the Central Sierra Snow Lab in 1948. Robert W. Gerdel, Ph.D., lead physicist of the new lab located near Donner Pass, and project director B. Lyle Hansen developed the first nuclear snow gage, which used radioactive material to measure the water content of the snowpack. Hansen was a wiz at designing innovative equipment like the radioisotope snow profiler. Gerdel and Hansen took a small capsule of radioactive cobalt-60 to a remote location where the material was placed at ground level and a Geiger counter suspended by a cross arm 15 feet above. As the emitted gamma rays passed through the winter snowpack, collisions with water molecules lowered their energy level, which indicated the amount of water in the snow. The Geiger counters were rigged with radio-transmitters so that their measurements could be relayed in real time to the snow lab, but with the idea that ultimately off-site hydrologists in Sacramento or San Francisco could also receive the signals. Hansen was later part of a team that developed the first heated drill bit to extract cores from the Greenland ice sheet. Information revealed by annual layers in the cores ultimately led to the discovery of previous rapid climate changes on Earth.
Beginning in the 70s, steel-mesh pillows were installed in western mountain ranges to try to eliminate manual sampling. Snow pillows are filled with liquid anti-freeze and placed over a weight sensor that is powered by electricity produced from solar panels. As the snowpack increases over a winter season, its weight pushes down on the pillow and the sensor underneath. The weight is calculated into snow-water equivalent. Today, almost 900 of these inert pillows produce near real-time data that is relayed by signal antennae to Western Regional Climate Center. This snowfall telemetry system is called SNOTEL.
Currently, two innovative methods adapted for snow hydrology by the National Oceanic and Atmospheric Administrationare operational. In 2017, NASA started a program called SnowEx that employed airborne gamma-ray detection and Light Detection and Ranging technology (lidar) to develop systems that can effectively survey vast expanses of remote mountain snowpacks. Airborne gamma detectors measure background radiation emitted from soil and rock. Gamma emissions from naturally occurring elements such as potassium, uranium and thorium interact with water molecules in the snowpack, which can be analyzed to determine snow-water equivalent. The SnowEx program hopes to eventually equip orbiting satellites with remote sensing technology for planet-wide accuracy.
Lidar is a remote-sensing method that combines features of radar (radio-wave navigation used by ships and planes) and sonar (underwater detection using sound for submarines). The lidar apparatus spins rapidly, firing invisible laser beams in all directions. It measures distance and creates a virtual 3-D map with GPS coordinates of everything it can see. For aerial snow surveying, the lidar is mounted beneath an airplane and flown over the sample zone. The results are compared with a previously acquired lidar map of the area bare of snow (snow-off and snow-on).
Snow-depth height and high-resolution horizontal snowpack profiles provide hydrologists with key snow-water equivalent data needed for forecasting runoff. The technology works well in densely forested areas and has applications in avalanche research. When combined with ground-based lidar and GPS sensors, accuracy is measured within centimeters. Lidar is also a key component — along with GPS — in self-driving vehicle technology.
