Snow cover, snowmelt timing and stream power in the Wind River Range, Wyoming

TLDR: In this article, the authors studied the relationship between the amount of water in a snowpack and stream discharge in the Wind River Range (WRR) of western U.S. and found a statistically significant trend at the 95% confidence level (or higher) of increasing weekly maximum air temperature for three out of the five meteorological stations studied.

About: This article is published in Geomorphology.The article was published on 2012-01-15 and is currently open access. It has received 60 citations till now. The article focuses on the topics: Snowmelt & Stream power.

Figures

Fig. 1. Base map of theWind River Range, Wyoming, and vicinity developed from the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM). Locations of the five meteorological stations and six streams used in this work are shown. Three elevation zones are also shown: yellow and peach are the 2500- and 3000-m contours, respectively, and white represents areas N3500 m. Streams and rivers are shown in light blue or dark blue with the dark blue indicating the streams used in the present study. The white rectangle on the image (inset) shows the location of the larger image. Locations of streams and the Continental Divide (black line) were obtained from the U.S. Geological Survey.

Table 4 Weekly-mean minimum and weekly mean-maximum air temperature trends (°C) per decade for five stations in and near the Wind River Range, Wyoming, 1970–2009. Trends that are statistically significant (at the 95% confidence level or higher) using a two-tailed T-test, are shown in bold.

Fig. 4. Regression relationship fromwhich amount of (volume) stream discharge can be predicted if the percent basin coverage is known on 30 April for the lowest elevation zone (2500–3000 m) of our study area in the Wind River Range. This relationship is based on 10 years of MODIS cloud-gap-filled (CGF) snow-cover data and stream discharge data (2000–2009). Spearman's Rank correlation, rs, for this relationship is 0.89.

Fig. 5. Stream power per unit length for Bull Lake Creek above Bull Lake is plotted for the 40-year study period (1970–2009). The trend toward decreasing stream power is significant at the 90% confidence level using a two-tailed T-test.

Fig. 3. Annual hydrographs composed of averagemean daily flows for each decade from the Wind River near Dubois in the Wind River Range, Wyoming; mean flow values of each day were computed for each decade from daily mean flow data. Data were missing between 1992 and 2001, so the decade of 1990–1999 includes only two years, and the decade of 2000–2009 includes only nine years (discharge data for the Wind River near Dubois for the decade of the 2000s began on 1 May 2001 so data from 2000 are not available).

Table 1 Spearman's Rank correlation, rs, for percent of basin (2500–3000 m elevation) covered by snow on three dates (2000–2009) versus total stream discharge volume from five streams: Bull Lake Creek above Bull Lake, Dinwoody Creek above Lakes, Green River at Warren Bridge, Little Popo Agie River near Lander and Wind River near Dubois. The Spearman's Rank correlation significance of deviation from zero values are shown in parentheses, where the lowest values indicate the most significant correlations. Note that the maximum-monthly discharge correlation values generally explain more of the variation than do the daily or seasonal values.

Frequently asked questions

Q1. What are the contributions in "Snow cover, snowmelt timing and stream power in the wind river range, wyoming" ?

Hall et al. this paper investigated the relationship between air temperature and snow cover in the Wind River Range ( WRR ) from 2000 to 2009, and to address the influence of changing conditions of the snowpack on the amount and timing of snowmelt, and stream power. 

Q2. What is the effect of cloud cover on the accuracy of the map?

Persistence of cloud cover following the last clear observation of the surface causes confidence in the accuracy of the cloud-gap-filled snow map to erode along with age of the last observation. 

Q3. What is the common reason for the lower elevations?

Warmer air temperatures alsomaybeassociatedwith less total extentof snowcover (see for example, Foster et al., 1983; Groisman et al., 1994; Cohen and Fletcher, 2007) especially at the lower elevations. 

Q4. What is the effect of the slope of the stream bed on the rs?

The ability of a stream to erode the stream bed is dependent in part upon the slope of the bed and the particle size of the sediment load. 

Q5. What is the effect of the snowmelt on stream power?

In addition to the influence of the amount of snow and the timing of melt on water resources, stream power is also affected by the mountain snowpack. 

Q6. What is the largest glacier in the continental U.S. outside of Washington State?

The WRR contains 25 of the 38 named glaciers in Wyoming, including Gannett Glacier (3.3 km2) which is the largest glacier in the continental U.S. outside of Washington State (PDX, 2010b). 

Q7. What is the effect of the warmer weather on the streamflow?

The fraction of annual streamflow that runs off during late spring and summer has declined by 10–25% since the 1950s because of warmer winter and spring weather (Cayan et al., 2001), and snowmelt runoff arrives 1–3 weeks earlier in many mountain basins in the western U.S. (Stewart et al., 2005; Lundquist et al., 2009). 

Q8. Why is the snowpack and glacier extent so important?

Because the majority of the water supply in the western U.S. (N70%) comes from snowmelt (and to a much-lesser extent, from glacier melt), analysis of the snowpack and glacier extent⁎ 

Q9. What is the effect of the lower temperatures on the stream discharge?

In many high-elevation streams in the western U.S. a reduction has occurred in the portion of annual stream discharge occurring during spring and early summer, that fraction of the streamflow attributable to spring snowmelt (see for example, Dettinger and Cayan, 1995; Cayan et al., 2001). 

Q10. What is the result of the rank correlation analysis?

The result is the rank correlation coefficient, rs, and the two-sided significance of its deviation from zero where the significance is a value in the interval [0.0, 1.0], and the lowest values indicate the most significant correlations. 

Q11. What is the reason for the earlier onset of spring-like weather in the western United States?

Earlier onset of spring-like weather has been documented in the western United States since at least the late 1970s; the warm episodes are related to larger-scale atmospheric conditions across North America and theNorth Pacific (Cayan et al., 2001;Mote, 2003;Mote et al., 2005). 

Q12. How did the authors reduce the resolution of the DEM?

to facilitate its use, the authors degraded the resolution of the DEM to 300-m using a simple averaging technique to reduce the size of the data files. 

Q13. How was the stream power calculated for Bull Lake Creek above Bull Lake?

Stream power was calculated for Bull Lake Creek above Bull Lake by determining the slope of the stream channel determined from the SRTM DEM using the full 30-m resolution.