watervulnerability
watervulnerability
watervulnerability
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Chequamegon-‐Nicolet National Forest Watershed Vulnerability Assessment, Eastern Region (R9)<br />
data is available for 14 global circulation models (GCMs) and three future scenarios for greenhouse gas<br />
emissions (A2, A1B, B1). It was developed by downscaling the coarse-scale climate projections of the<br />
GCMs. The ideal approach for climate change analyses would be to model the effects for all 14 GCMs<br />
and all three scenarios to evaluate the full range of potential climate change impacts. Given limited time<br />
and resources, this assessment used just one GCM, the GFDL-CM2.0, and one scenario for one pixel of<br />
data located on the Park Falls unit of the CNNF. The A1B scenario was selected because it provides an<br />
intermediate level of greenhouse gas emissions relative to the other scenarios.<br />
Wetlands<br />
Potential changes in wetland hydrology were determined using the Peatland Hydrologic Impact Model<br />
(PHIM) (Guertin et al. 1987; Brooks et al. 1995). PHIM is a physically-based, continuous simulation<br />
model for predicting water yield and streamflow from peatland and upland watersheds typical of the<br />
northern Great Lakes region.<br />
The PHIM was run with 40 years of historic climate data (1961-2000) and 20 years of projected climate<br />
data (2046-2065). The potential effect of climate change on bog hydrology was evaluated by determining<br />
differences in average annual and seasonal runoff and evaporation from the upland-peatland complex, and<br />
average annual and seasonal water level in the bog. The results were extrapolated to all HUC-6<br />
watersheds encompassing the National Forest based on the proportion of total wetland and acid wetland<br />
in each HUC-6 watershed.<br />
Groundwater Recharge<br />
The groundwater recharge portion of the analysis focused on the Park Falls unit of the Forest to take<br />
advantage of a recently initiated project characterizing groundwater resources on this portion of the<br />
Forest. This project is being conducted by the Wisconsin Geological and Natural History Survey<br />
(WGNHS) and United States Geological Survey (USGS).<br />
Potential changes in groundwater recharge were determined for the Park Falls unit using the Soil Water<br />
Balance Model (SWBM) (Westenbroek et al. 2010; Dripps and Bradbury 2007). The SWBM estimates<br />
recharge using gridded watershed data and tabular climatic data. The watershed data include soil water<br />
capacity, hydrologic soil group (HSG), flow direction, and land use.<br />
The results of the Park Falls modeling were extrapolated to all HUC-6s encompassing the National Forest<br />
based on the proportion of HSG in each HUC-6. Watersheds with no or reduced recharge were considered<br />
most vulnerable while those with increases in recharge were considered least vulnerable or most resilient.<br />
Infrastructure-Culverts<br />
The analysis included four primary steps: (1) evaluating climate change projections to determine the<br />
potential for increases in flood magnitudes, (2) reviewing culvert sizing criteria and hydraulic modeling<br />
results, (3) determining road-stream crossing density and runoff potential for HUC-6s within the CNNF,<br />
and (4) characterizing the vulnerability of HUC-6s to increased flood flows and failure of culvert<br />
infrastructure based on steps 1-3.<br />
WICCI summary data were evaluated for evidence that flood flows may increase in the future. Key data<br />
used for this evaluation were projections for the frequency of 1-, 2-, and 3-inch rainstorms and for annual<br />
and seasonal precipitation and air temperatures.<br />
238 Assessing the Vulnerability of Watersheds to Climate Change