AGU 2017: 50 years of change at 14 headwater watersheds in Wyoming

50 years of change at 14 headwater snowmelt-dominated watersheds in Wyoming

2017

AGU Fall Meeting, New Orleans

Abstract

Wyoming is a headwater state contributing to the water resources of four major US basins: Columbia River, Colorado River, Great Basin, and Missouri River. Most of the annual precipitation in this semi-arid state is received at high elevations as snow. Water availability for drinking water supply, reservoir storage, industrial, agricultural, and ecological needs – all depends on the variable and potentially changing annual snowmelt. Thus, characterizing snowmelt and snowmelt-dominated runoff variability and change at high-elevation headwater watersheds in Wyoming is of utmost importance.

Next to quantifying variability and changes in total precipitation, snow-water equivalent (SWE), annual runoff and low flows at 14 selected and representative high-elevation watersheds during the previous 50 years, we also explore past watershed disturbances. Wildfires, forest management (e.g. timber harvest), and recent bark beetle outbakes have altered the vegetation and potentially the hydrology of these high-elevation watersheds.

We present a synthesis and trend analysis of 49-75 complete water years (wy) of daily streamflow data for 14 high-elevation watersheds, 25-36 complete wy of daily SWE and precipitation data for the closest SNOTEL stations, and spatiotemporal data on burned areas for 20 wy, tree mortality for 18 wy, timber harvest during the 20^th century, as well as overview on legacy tie-drive related disturbances. These results are discussed with respect to the differing watershed characteristics in order to present a spectrum of possible hydrologic responses.

The importance of our work lies in extending our understanding of snowmelt headwater annual runoff and low-flow dynamics in Wyoming specifically. Such regional synthesis would inform and facilitate water managers and planners both at local state-wide level, but also in the intermountain US West.

(the text is as it appears @AGU2017 conference site)

Details

Original poster size: 170 x 114 cm

Summary of watershed characteristics (ranked by watershed area size) and Sen's slope estimator results for SWE/precipitation ratio, SWE, precipitation, annual runoff, snowmelt runoff, post-snowmelt baseflow, and annual 7-day minima.

Timber harvest footprint at the watersheds (Top 5 are mapped). Most of the stand clear-cut was done between the '50s and the '60, while the patch clear-cut continued in the '80s and '90s of 20th century. North Brush and Rock Creek (both are in the Medicine Bow Range) are the two most impacted watersheds.