watervulnerability

Chequamegon-­‐Nicolet National Forest Watershed Vulnerability Assessment, Eastern Region (R9)
to show a small increase in precipitation during fall, winter, and spring for northern Wisconsin. This
additional water, available at the time of year when evapotranspiration is low, will most likely go to
satisfying soil moisture deficits and recharging groundwater.
Both the absolute potential groundwater recharge and the difference for the two time periods varied by
soil type. Highly permeable soils have greater potential recharge and showed a greater positive difference
than heavy or peatland soils. Average potential recharge ranged from 13.5 inches for HSG A to 3.5 inches
for HSG D (Table 3). HSGs A, B, C, and D had average increases of 1.3, 0.8, 0.7, and 0.0 inches,
respectively (Table 3, Figure 13). HSGs are based on runoff potential when soils are thoroughly wet,
considering texture, presence of impermeable layers, and depth to water table. HSG A soils have low
runoff potential and consist primarily of sand and gravel. HSG B soils have moderately low runoff
potential, consisting of mostly loamy sand and sandy loam textures. HSG C soils have moderately high
runoff potential and finer textures such as loam, silt loam, sandy clay loam, clay loam and silty clay loam.
Hydrologic
Soil Group
Area
(acres)
Avg. Annual Potential Recharge
(inches)
2046-
2065
1971-
1990
249 Assessing the Vulnerability of Watersheds to Climate Change
Mean
Difference
A 62,351 14.88 13.54 1.34
B 96,384 11.51 10.75 0.76
C 37,134 7.16 6.51 0.65
D 116,218 3.47 3.51 -0.04
Water 14,144 1.19 1.17 0.02
Total 326,231 8.35 7.81 0.54
Table 3. Summary of average annual potential groundwater recharge (inches) by hydrologic soil group for HUC-6
watersheds on the Park Falls Unit of the Chequamegon-Nicolet NF
HSG D soils have high runoff potential because of clayey textures, an impermeable layer within 20
inches, or water table within 24 inches. Based on the results of the groundwater recharge modeling, HSG
As were considered least vulnerable or most resilient to climate change impacts while HSG Ds were
considered most vulnerable or least resilient.
Because the response of potential groundwater recharge to the projected climate change varied by HSG,
this information was used to estimate potential groundwater recharge and vulnerability to climate change
for each HUC-6 on the Forest. An HSG index was developed for each HUC-6, based on the areaweighted
proportion in each HSG, with A=1, B=2, C=3, and D=4. This index was used, along with the
presence of surface water features, to classify the watersheds into four classes: groundwater recharge
(HSG index2.837). Regression analysis was used to relate this index to the future and historic potential
groundwater recharge for the HUC-6s on the Park Falls unit. These regression equations were then used
to estimate and summarize potential historic and future recharge for all HUC-6s across the Forest.