Snow Drought Risk and Susceptibility in the Western United States and Southwestern Canada

Abstract

In western North America (WNA), mountain snowpack supplies much of the water used for irrigation, municipal, and industrial uses. Thus, snow droughts (a lack of snow accumulation in winter) can have drastic ecological and socioeconomic impacts. In this study, the historical (1951–2013) frequency, severity, and risk (frequency × severity) of dry, warm, and warm and dry snow droughts are quantified at the grid‐cell and ecoregion scale for snow‐dominated regions in the western United States and southwestern Canada (sWNA). Based on multiple linear regression analysis, relationships between mean winter temperature, snow drought risk, and snow water equivalent sensitivity are explored. Piecewise linear regression is used to identify temperature thresholds for mapping temperature‐related snow drought susceptibility. Results highlight spatial differences in snow drought regimes across sWNA and reveal that temperature thresholds exist at −3.1 °C (±0.3 °C) and 1.4 °C (±0.3 °C), above which the warm snow drought risk increases more rapidly. Approximately 3% of the nonglaciated snow storage in this region has high susceptibility to temperature‐related snow drought, representing 11 km3 of water, or approximately one third the capacity of Lake Mead. Under a +2 °C climate scenario, an additional 8% (28 km3) of this snow storage volume will transition to high susceptibility.

Climate change impacts on snow and streamflow drought regimes in four ecoregions of British Columbia

“…While several recent studies have focused of snow drought (Dierauer et al, 2019;Mote et al, 2016;Harpold et al, 2017) and its hydrological impacts (Cooper et al, 2016;Sproles et al, 2017;Hatchett and McEvoy, 2018), no previous studies have explicitly related climate change impacts on snow drought to subsequent impacts on summer low flows and summer streamflow drought. In this study, generic GW-SW models of headwater catchments were combined with downscaled climate change projections for two different RCPs.…”

“…In general, snow drought regimes in all catchments shift toward more frequent, higher severity warm, and warm and dry, snow droughts, and less frequent, lower severity dry snow droughts. As documented by Dierauer et al (2019) and shown in Figure S9, the response of warm snow drought risk to increased winter temperature is non-linear. A 2°C increase in the mean winter (1-Nov to 1-Apr) temperature corresponds to a substantially larger increase in warm snow drought risk for the Capilano catchment as compared to the Fort Nelson catchment.…”

“…To investigate how different snow drought types impact seasonal low flows, snow droughts were classified using the methodology outlined in Dierauer et al (2019). With this method, winters with below-normal peak snow water equivalent (SWE) are classified as warm, dry, or warm and dry snow droughts based on winter precipitation (Pw) and winter thawing degrees (TDw).…”

“…Moreover, no studies have completed a combined analysis of snow drought and streamflow drought regimes in the context of climate change. Dierauer et al (2019) has shown that temperature-related snow drought risk increases with increasing mean winter temperatures and identified temperature thresholds above which hydroclimatic change "accelerates". As temperatures rise, increased frequency and severity of temperature-related snow drought will likely lead to increased frequency and severity of summer streamflow droughts.…”

Spatiotemporal Variability of Twenty‐First‐Century Changes in Site‐Specific Snowfall Frequency Over the Northwest United States

“…The nonlinearity in snowfall frequency declines over the twenty‐first century suggests that associated impacts will accelerate in future decades without implementation of mitigation strategies, which has implications for short‐term versus long‐term planning. This is particularly important in lower elevation locations, which are more sensitive to changes in temperature (Mote et al, ) and, thus, more susceptible to snow droughts (Dierauer et al, ). Yet even in a stationary climate, the interplay between snowpack and its surrounding environment (e.g., wildfire, canopy density, and slope angle) is integral to water storage.…”