Cooperator: Dane County
Project Chief: Stephen M. Westenbroek
Location: Dane County
Project Number: 9KO37
Period of Project: June 2004–December 2004
Problem
The Yahara River Watershed in Dane County, Wisconsin is one of the most rapidly urbanizing areas within the state and the water-resource problems in the watershed are accelerating along with the increasing development. The Yahara River is part of a chain of lakes including Lake Mendota, Lake Monona, Lake Waubesa, and Lake Kegonsa. Dams at the outlets of Lake Mendota, Lake Waubesa, and Lake Kegonsa are operated to maintain stable lake levels, to provide flood protection benefits, and to enhance aquatic resources in the river and associated wetlands. The urban areas—including the cities of Madison, Middleton, Monona, McFarland, and Stoughton and the suburban area in Dane County—are all experiencing dramatic increases in the amount of impervious area, resulting in increasing stormwater runoff to the lakes and decreasing infiltration to the ground-water system. This development is creating a potential for more frequent and more severe flooding during wet periods and is also creating a water demand that results in more frequent and more severe drought conditions during periods of low flow. Increasing amounts of storm runoff also transport higher loads of sediment and nutrients from the impervious areas into the lakes.
In order to address these issues, the existing forecasting model used to manage the Yahara River system (operational model) needs to be updated. Further, there is a need for a long-range watershed model capable of evaluating the impact of future development on the Yahara River system (planning model).
Objective
The overall goal for this work is to develop a range of scope, schedule, and budget options associated with updating the current operational model and developing a comprehensive watershed planning model. Associated objectives of this study are to: (1) determine what data exists, and what data needs to be collected, (2) determine the most appropriate approach for updating the operational model, and (3) determine the approach required to develop the planning model.
Approach
To meet the objectives stated above, a screening model will be developed using the USGS Modular Modeling System (MMS). The screening model will be subjected to a sensitivity analysis. The results of the screening model sensitivity analysis will yield important information on what types of data are most important to any future model development activities. Such a sensitivity analysis will be useful regardless of what model framework is ultimately selected for the larger watershed modeling effort. The existing real-time operational model will be examined to determine the enhancements required to provide a functional tool for making decisions regarding the day-to-day operation of the dam control structures in the system.
The results of our examination of the existing operational model will be combined with sensitivity analysis results from the screening model. This will yield a set of criteria that can be used to select the type and complexity of a comprehensive watershed model needed to evaluate the surface-water resources of the Yahara River system.
Progress (July 2003 to June 2004)
A scoping-level watershed model for the Yahara River system was completed. Daily precipitation, lake level, and streamflow records were assembled and reviewed for the period 1954–2004. Analysis of the existing datasets suggests that additional streamgaging is needed at the outlets of Six-Mile and Starkweather Creeks.
Sensitivity analysis was performed for over 300 model parameters. The sensitivity analysis underscores that there are numerous sets of parameters that result in approximately the same model calibration statistics. This suggests that future model development efforts must include an exploration and quantification of the effects of non-unique model parameter sets.
Plans (July 2004–December 2004)
There are no plans to continue this work. Dane County will be issuing a request for proposals (RFP) for further model development work.
Reports
A letter report will be prepared summarizing the screening model results and defining the requirements for the comprehensive watershed model development. |
