Citation:

Chokshi, S., Bob McKane, J. Halama, A. Brookes, K. Djang, G. Mauger, P. North, P. Murphy, J. McDermott, M. Totman, AND S. Dickerson-Lange. Modeling Watershed Response to Climate Change and Snow Dynamics in the Puget Sound Basin. Interagency Conference on Research in the Watersheds (ICRW8), Corvallis, OR, June 05 - 08, 2023.

Impact/Purpose:

The main objective of this research has been to establish a scientifically sound watershed simulation model to assess the effects of climate change on snow dynamics and ultimately watershed conditions for three watersheds in the Puget Sound Basin. Major watersheds in this area may experience expedited effects of climate change due to alpine and sub-alpine terrain, while also experiencing varied climate conditions across watershed extents. Much of this area is currently undeveloped and owned by federal agencies, like the National Park Service and National Forest Service, or tribal communities. It is important to understand how these watersheds will respond to changing temperature and precipitation patterns, particularly regarding summer low flows and snowpack dynamics. This information can help provide an understanding of future watershed conditions and inform management decisions when considering development, especially in mid to high-altitude forest ecosystems. 

Description:

Visualizing Ecosystem Land Management Assessments (VELMA) is a spatially explicit process-based ecohydrological model used to assess potential watershed conditions. As part of the Puget Sound Integrated Modeling Framework connecting terrestrial, freshwater, marine, and social systems, the VELMA team is developing model outputs for 24,000 km2 of land across 24 watersheds around the Puget Sound Basin for various future climate and land cover scenarios. VELMA models variables at a daily timestep per cell (plot scale) that are averaged across each delineated watershed extent. The Puget Sound Basin ranges across multiple climate types, from the temperate rainforests of the Olympic Peninsula to the alpine zones of Mount Rainier and the North Cascades. The headwaters of major rivers occur at elevations of 2000-4300 meters, before flowing into the Puget Sound. Watersheds in this region experience wide ranges in precipitation and temperature between mountainous headwaters and flat outlets, and landscapes tend to be dominated by coniferous forest. As climate change and extreme weather events impact snow storage in the Puget Sound Basin, it is important to understand watershed response, particularly regarding summer low flows and peak storm events. The snow model in VELMA introduces static parameters such as snowmelt rate, snowmelt temperature, snow formation temperature, and rain-on-snow in conjunction with provided historical weather data or specified climate scenarios affecting multi-scale spatial and temporal hydrologic responses. After calibrating streamflow against USGS gauge stations based on historic climate data for 1990-2021, we will use VELMA to model variables of interest, including streamflow, snow depth, snow melt, snow line, and soil moisture, into the future using Livneh Representative Concentration Pathway (RCP) intermediate (4.5 W/m2) and extreme (8.5 W/m2) climate scenarios. This presentation will examine how VELMA models variables of interest using Livneh RCP 4.5 and 8.5 climate projection data until 2100 for temperature and precipitation for three watersheds encompassing a range of climate zones across the Puget Sound Basin.

Record Details: