Assessing the accuracy and variability of estimating snow water equivalent from lake water pressure

Abstract

Seasonal snowpack is a crucial global water resource, but measuring it accurately poses challenges. Measurements of snow water equivalent (SWE) from existing instruments are susceptible to significant bias and often provide data only at the point scale. The global network of SWE sensors is sparse and bias towards lower elevations in the mountains, limiting their effectiveness in informing hydrologic models and forecasts. A promising new method has been proposed to estimate SWE from lake pressure in frozen alpine lakes. To gain a more complete understanding of the capabilities of this method, we conducted an alpine study site at Mystic Lake (45.54, -110.93) in Southwest Montana, USA. We present how noise in the water pressure signal can add significant uncertainty to SWE methods, and we present methods for smoothing the data to achieve more reliable estimates in employing this method to measure SWE. We find that there is substantial variability between SWE observed over the ice surface and adjacent ground surfaces during the study period, underscoring the challenges of measuring snow in the mountains. The results of this study demonstrate that estimating SWE from lake water pressure can provide valuable insights into basin hydrology and easy-to-implement observations of SWE. However, careful consideration and site-specific planning are requisite for accurate and representative SWE estimates.