Mid-Term Results of the Lake Mendota Priority Watershed Project

MID-TERM RESULTS OF THE LAKE MENDOTA PRIORITY WATERSHED PROJECT

Carolyn Rumery Betz1, Pete Jopke2, Kevin Connors2 and Richard Lathrop3

Background

Lake Mendota currently suffers from the effects of polluted runoff from its 232-mi2 watershed (Map 1). Land use in the watershed is 65% agricultural land, 20% existing urban area, 5% wetlands and woodlands, and 10% open water or internally drained land. The watershed includes two counties, three cities (including most of the City of Madison), seven villages, and 12 towns. The watershed was selected in 1993 as a priority watershed project by the Wisconsin Department of Natural Resources’ Nonpoint Source Pollution Abatement Program. The goal of the project is to improve the water quality of the lake by reducing nonpoint sources of pollution from the watershed.

A 3-year planning and inventory period occurred between 1994 and 1997. Water resources appraisal monitoring was conducted to assess the quality of the streams, groundwater, and wetlands in the watershed. A thorough analysis of historical monitoring data available on Lake Mendota was conducted since the lake has been extensively studied for the better part of a century. A land resources inventory was carried out to determine the pollutant loading from cropland, barnyards, existing urban areas, and areas undergoing transition from rural to urban uses. A survey was conducted of a representative sample of farmers in the watershed to assess their nutrient and pesticide management practices. A plan was produced presenting the results of the inventory, outlining the goals of the project, methods of implementation, and a recommended budget for the 11-year implementation period (Betz, 2000).

Results

The results of the water resources appraisal indicated that almost all stretches of streams in the watershed are suffering from the effects of nonpoint source pollution and only partially meet their potential biological uses. Token Creek does have the potential of becoming a naturally reproducing trout stream. Groundwater contamination is one of the most significant problems in the watershed. About 65% of all wells tested exceeded the health standard for nitrogen of 10 mg/L. Almost 75% of farmers in the watershed do not credit or under-credit manure applied to their fields.

1 Watershed Planner, Wisconsin Department of Natural Resources, P.O. Box 7921, WT/2, Madison, WI 53707, (608) 258-8699, [email protected], 2 Project Manager and County Conservation, Dane County Land Conservation Department, 1 Fen Oak Ct., Madison, WI , 3 DNR, 1350 Femrite Dr., Monona, WI 53716, and UW Center for Limnology, 680 North Park St., Madison, WI 53706 1

The water quality goal for Lake Mendota is to reduce the concentration of spring total phosphorus (P) in the lake to less than 0.074 mg/L (Lathrop, 1998). Modeling results indicate that this P level will result in a decrease in the concentration of blue-green algae to less than 2 mg/L, or the point at which algae form nuisance blooms. Given the current annual P loading, the likelihood on any given summer day of a nuisance algae bloom occurring is 50% of the time, or one out of every two days on average over a number of summers. The goal is to decrease the likelihood of a nuisance algal bloom to 20% of the time, or one out of five days on average over a number of summers. In a year with high precipitation and hence high runoff into the lake, nuisance algal blooms would be more likely that summer, even with the implementation of recommended best management practices. To achieve this goal, P loading from the watershed must be reduced by about 50%, or 37,000 pounds.

The water quality goals can be achieved by reducing sediment and phosphorus loadings. The sediment reduction goals are as follows: a 40% reduction from cropland, a 50% reduction from streambanks, a 40% reduction from existing urban areas and an 80% reduction from construction sites. The phosphorus goals are a 40% reduction from cropland, a 50% reduction from streambanks, a 75% reduction from barnyards, a 20% reduction from existing urban areas, and a 60% reduction from construction sites.

6% 8% Cropland (48%) Cropland (58%) 21% 23% Existing Urban(6%) Existing Urban (11%) 48% Construction Sites (19%) 58% Construction (23%) 19% Barnyards (21%) 11% Streambanks (8%) 6% Streambanks (6%) Fig. 1 Sediment loading in the Fig. 2 Phosphorus loading in the Lake Mendota Watershed, 1997 Lake Mendota Watershed, 1997

Implementation

The project has been in the implementation phase since 1998 and will continue through 2008. At the rural level, 662 landowners are eligible to participate, and thus far, over 160 cost-share agreements have been signed using federal and state watershed project funds. The majority of the cost-share agreements have been for nutrient management planning. Other practices that have been implemented are clean-water diversions around barnyards, proper well abandonment, water management structures, and streambank protection.

At the urban level, all of the municipalities have adopted new, performance-based construction site erosion control ordinances that are being actively enforced. Dane County has recently adopted a new storm water management ordinance that municipalities are required to follow by mid-2002. Most municipalities have also implemented at least one new storm water management control structure using project grants.

Conclusion

The initial enthusiastic phase of sign-ups has already taken place, and despite having nearly 7 years left in the implementation phase, there are quite a few obstacles to overcome in order to reach the project goals. These include inadequate staffing to meet the needs of the project, uncertainty of budgets, changing rules of the NPS program, unwillingness of landowners to do more than the minimum that is required of them, reluctance of municipalities to engage in new grant opportunities with the state, and most importantly, the timing of the project versus the lifetime of the farm or a municipality. The 11-year implementation period may prove to be but a small window in which to change behaviors in the long life of a family farm operation or to a community. If the Lake Mendota Priority Watershed Project is to significantly improve the water quality of the lake, changes in rural and urban behaviors will have to extend beyond the project implementation period.

References

Betz, C.R. (ed.), 2000. Nonpoint Source Control Plan for the Lake Mendota Priority Watershed Project. Wisconsin DNR. WT-536-00 REV.

Lathrop, R.C, S.R. Carpenter, C.A. Stow, P.A. Soranno, and J.C. Panuska. 1998. Phosphorus loading reductions needed to control blue-green algal blooms in Lake Mendota. Can. J. Fish Aquat. Sci. 55:1169-1178.