Advancing Snow Observation Systems to Improve Hydrologic Prediction in Mountain Headwaters

Snow energy balance, particularly radiation balance, is monitored only at a limited number of well-instrumented, research-focused snow study sites in the western United States. This lack of observations limits our ability to force or validate process-based snow models in mountain terrain, an important hurdle to operational adoption. To address this gap, we have prototyped a low-cost, low-power, transportable snow monitoring system capable of transmitting near-real-time snow energy balance relevant observations. Each instrumentation suite measures incoming and reflected broadband shortwave radiation, incoming and emitted longwave radiation, air temperature/relative humidity, and snow depth. Including sensors, power, data logging, and communications infrastructure, each site costs less than USD $10,000, enabling deployment at a scale not feasible with conventional research stations. The systems have been deployed at 11 sites across snow-dominated headwater catchments in the Intermountain West, more than doubling the current number of snow radiation balance observation sites. Two sites are co-located with research sites for validation, and observations are used to drive the 1d SNOBAL model to assess the sensitivity of simulated snow water equivalent to lower-cost instrumentation. This approach complements existing snow monitoring networks, including the ~900-site SNOTEL (Snowpack Telemetry) network, which provides long-term observations for snow mass balance monitoring and index-based streamflow forecasting. SNOTEL sites are intentionally located in sheltered, mid-elevation forest openings and do not capture spatial variability, nor do they measure radiation balance. Low-cost, distributed energy balance observations provide a pathway to complement and extend the observational capabilities of current networks.