Estimates of Glacier Mass Loss and Contribution to Streamflow: Wind River Range (Wyoming, USA)

The Wind River Range is a continuous mountain range approximately 160 km in length in west-central Wyoming. The Wind River Range is host to roughly 680 snow and ice bodies with 63 of these considered glaciers including seven of the ten largest glaciers in the American Rocky Mountains. The presence of glaciers results in meltwater contributions to streamflow during the late summer (July, August, and September – JAS) when snowmelt is decreasing, temperatures are high, precipitation is low, and irrigation demand continues. Most studies indicate that the glaciers in the Wind River Range have been retreating since the 1850’s, the approximate end of the Little Ice Age. Thus, the quantification of glacier meltwater (e.g., volume, mass) contributions to late-summer/early-fall streamflow is important given this resource is dwindling due to glacier recession.

The current research expands upon previous research efforts and identified two glaciated watersheds, one on the east slope (Bull Lake Creek) and one on the west slope (Green River) of the Wind River Range in which unimpaired streamflow is available from 1966 to 2006. Glaciers were delineated within each watershed and area estimates (with error) were obtained for the years 1966, 1989 and 2006. Glacier volume (mass) loss (with error) was estimated using empirically based volume-area scaling relationships. For 1966 to 2006, glacier mass contributions to JAS streamflow on the east slope were approximately 8% while on the west slope were approximately 2%. The volume-area scaling glacier mass estimates compared favorably with measured (stereo-pairs remote sensed data) estimates of glacier mass change for three glaciers (Teton, Middle Teton, Teepe) in the nearby Teton Range and one glacier (Dinwoody) in the Wind River Range. While glacier mass contribution to JAS streamflow was estimated at 8% (east slope) and 2% (west slope) from 1966 to 2006, an increase was observed during the period of 1989 to 2006 (>11% - east slope and >3% - west slope). Historic climate data, including precipitation (snowpack) and temperature (JAS average) showed a decrease in snowpack and rapid increase in temperatures during the 1989 to 2006 period, which most likely explains this increase in glacier melt.