watervulnerability

Grand Mesa, Uncompahgre and Gunnison National Forest Watershed Vulnerability Assessment, Rocky
Mountain Region (R2)
These two scenarios describe a range in climate change predictions that may occur on the GMUG. The
predictions are consistent with the state-wide changes described above, and further refine the potential
effects that may be seen on the GMUG.
Table 1 displays the predicted annual and seasonal changes in precipitation and temperature for the
“moderate” scenario.
Season Precipitation (%) Temperature (˚C) Temperature (˚F)
Annual ~0.0 +2.0 to +3.0 +3.6 to +5.4
Winter +15.0 +2.0 +3.6
Spring -12.0 +2.5 +4.5
Summer -15.0 +3.0 +5.4
Fall +4.0 +2.5 +4.5
Table 1. Temperature and Precipitation Changes for “Moderate” Climate Change Scenario developed
by Barsugli and Mearns for the Gunnison Basin
Predicted changes under the “moderate” scenario include:
1. Increase in annual temperatures of 2-3 ˚C (3.6-5.4 ˚F).
2. No substantial change in annual precipitation, but an increase in cool season precipitation and a
decrease in warm season precipitation.
3. Decrease in annual natural stream flows of 5% to 10%, due to increased temperature, even if
annual precipitation remains the same.
4. Warming temperatures lead to a later accumulation of snow in the fall and earlier snowmelt in the
spring. However, because of the increased precipitation in winter and the generally cold, highelevation
nature of the upper Gunnison basin, the mid-winter snowpack may be similar to the
present.
5. Snowmelt-driven stream flow will occur earlier in the spring by about a week on average. (Note:
this shift is due to warming and does not include the effects of dust-on-snow, which can result in
an even earlier shift in snowmelt.)
6. The earlier melt, along with decreased summertime precipitation and increased summertime
temperatures, results in lower amounts of water stored in the soils during summer and fall.
Table 2 displays the predicted annual and seasonal changes for the “more extreme” scenario. The “more
extreme” scenario is warmer and drier than the “moderate” scenario.
83 Assessing the Vulnerability of Watersheds to Climate Change