watervulnerability

Grand Mesa, Uncompahgre and Gunnison National Forest Watershed Vulnerability Assessment, Rocky
Mountain Region (R2)
• Colorado Department of Water Resources (surface and groundwater sources, water rights
information)
• Colorado Department of Public Health and Environment (source water protection areas)
SCALES OF ANALYSIS
Area Assessed
The WVA was completed for the entire Forest and surrounding areas, in general; and specifically for
those portions of the GMUG within watersheds that were mostly on National Forest System lands.
Analysis Units
Several different analysis units were used as part of this WVA. Analyses were summarized primarily at
the subwatershed level (-6), as delineated by the sixth level (12-digit) of the hydrologic unit hierarchy in
the US Geological Survey (USGS) National Hydrography Dataset (NHD) and the US Department of
Agriculture (USDA) Natural Resources Conservation Service (NRCS) Watershed Boundary Dataset
(WBD). There are 205 subwatersheds within the assessment area for this WVA.
Some subwatersheds were merged together for analysis purposes so that complete catchment basins were
delineated (some HUC-6 subwatershed delineations from NHD/WBD separated upper portions of
watersheds from lower portions). This resulted in 152 modified HUC-6 subwatersheds. These modified
HUC-6 subwatershed analysis units were used to summarize information on aquatic resource values, and
watershed risks described below as inherent sensitivities and anthropogenic stressors.
Anticipated climate changes, or exposure (also described below) were evaluated using several different
analysis units. Watersheds (HUC-5), delineated at the fifth level (10-digit) of the hydrologic unit
hierarchy in NHD/WBD were used to summarize predicted climate changes output by the VIC model.
There are 49 HUC-5 watersheds that overlap the assessment area for this WVA.
In addition, exposure was also evaluated using geographic areas that have similar climatic regimes. These
geographic areas also roughly correspond to areas used in Forest planning. Modified HUC-6
subwatersheds were aggregated into six geographic areas within the assessment area.
Figure 3 shows the original NHD/WBD HUC-6 delineations, the modified HUC-6s used for this analysis,
and the HUC-5 watersheds as they overlap the GMUG. Figure 4 shows the geographic overlap of the
modified HUC-6 subwatersheds and the GMUG.
67 Assessing the Vulnerability of Watersheds to Climate Change