Multiple Indicators of Extreme Changes in Snow-Dominated Streamflow Regimes, Yakima River Basin Region, USA

Abstract

Snow plays a major role in the hydrological cycle. Variations in snow duration and timing can have a negative impact on water resources. Excluding predicted changes in snowmelt rates and amounts could result in deleterious infrastructure, military mission, and asset impacts at military bases across the US. A change in snowpack can also lead to water shortages, which in turn can affect the availability of irrigation water. We performed trend analyses of air temperature, snow water equivalent (SWE) at 22 SNOTEL stations, and streamflow extremes for selected rivers in the snow-dependent and heavily irrigated Yakima River Basin (YRB) located in the Pacific Northwest US. There was a clear trend of increasing air temperature in this study area over a 30 year period (water years 1991–2020). All stations indicated an increase in average air temperatures for December (0.97 °C/decade) and January (1.12 °C/decade). There was also an upward trend at most stations in February (0.28 °C/decade). In December–February, the average air temperatures were 0.82 °C/decade. From these trends, we estimate that, by 2060, the average air temperatures for December–February at most (82%) stations will be above freezing. Furthermore, analysis of SWE from selected SNOTEL stations indicated a decreasing trend in historical SWE, and a shift to an earlier peak SWE was also assumed to be occurring due of the shorter snow duration. Decreasing trends in snow duration, rain-on-snow, and snowmelt runoff also resulted from snow modeling simulations of the YRB and the nearby area. We also observed a shift in the timing of snowmelt-driven peak streamflow, as well as a statistically significant increase in winter maximum streamflow and decrease in summer maximum and minimum streamflow trends by 2099. From the streamflow trends and complementary GEV analysis, we show that the YRB basin is a system in transition with earlier peak flows, lower snow-driven maximum streamflow, and higher rainfall-driven summer streamflow. This study highlights the importance of looking at changes in snow across multiple indicators to develop future infrastructure and planning tools to better adapt and mitigate changes in extreme events.

SNOTEL, the Soil Climate Analysis Network, and water supply forecasting at the Natural Resources Conservation Service: Past, present, and future

“…However, it also bears emphasizing that maintaining fixed SNOTEL monitoring locations over very long timeframes provides a crucial sentinel function. Such long‐term SNOTEL monitoring at permanent sites has enabled clear and direct observational detection and analysis of long‐term changes in mountain snow and climate attributable to global anthropogenic climate change (e.g., Mote et al, 2018; Surfleet & Tullos, 2013; Wagner et al, 2021) or other environmental shifts, like worsening wildfire threats (Giovando & Niemann, 2022; Smoot & Gleason, 2021) reflecting historical fire suppression and fuel‐load buildup, climate change, and growing human intrusions into forest lands. The need for that sentinel function will only increase going forward.…”

Channel Conveyance Variability can Influence Flood Risk as Much as Streamflow Variability in Western Washington State

“…Previous studies have shown dramatic declines in western United States snowpack (e.g., Mote, 2003; Mote et al., 2018) in concert with regional warming over the last century (May et al., 2018). This results in statistically significant increases in winter maximum streamflows as previously snow‐dominated basins transition toward rain‐dominated basins in winter (Wagner et al., 2021). Thus, changes in snowpack likely explain some of the observed shifts in the flow‐duration curve.…”

Earlier emergence of winter-spring maximum streamflow across Poland, 1981–2020

“…Moreover, winter warming and snow droughts may propagate into the summer streamflow droughts, which are projected to occur even more frequently in the future (Demaria et al 2016;Dierauer et al 2021;Patterson et al 2022). Thus, it is essential to understand how the timing of the winter-spring streamflow has changed over historical periods (Steward et al 2004;Hodgkins, Dudley 2006;Wagner et al 2021) and how the timing of peak flows is projected to shift in the future (Byun et al 2019).…”