This report describes low-flow characteristics of streams in the central Wisconsin River basin where streamflow data have been collected and presents equations for estimating low-flow characteristics at ungaged sites. Included are estimates of low-flow frequency at 34 gaging stations, flow duration at 24 gaging stations, and low-flow frequency characteristics at 18 low-flow partial-record stations and 131 miscellaneous sites.
Due to the large variability in low-flow characteristics, the central Wisconsin River basin was divided into four areas of similar geologic and topographic conditions.
Separate equations are provided for each area to estimate low-flow characteristics at ungaged sites and at sites where one base-flow discharge measurement is available. The equations were determined from multiple-regression analyses that related the low-flow characteristics at gaging stations and at low-flow partial-record stations to basin characteristics. Drainage area (A), hydraulic conductivity (K), soil-infiltration capacity (l), forest cover (F), base-flow index (Bf), and drift thickness (H) were the most significant characteristics in explaining the variations in low flow at ungaged sites.
The standard error of estimate (SE), provided for each equation, ranged from 10 to 140 percent. Equations with the lowest SB's were for the central sand plain area that contains relatively thick sand aquifers. The highest SB's were associated with equations for the area west of the Wisconsin River where thin glacial drift with fairly low permeability overlies crystalline rock.
The low-flow characteristics determined for all types of sites in the central sand plain area have the lowest SE's compared to other basins in the State. This is due to the sand deposits which yield a high and uniform base flow.
