Lake Prioritization for Protecting Swimmable Use

In a world with unlimited dollars for monitoring lakes and restoring lakes with impaired water quality there would be little need to prioritize activities. However, since there is a limited amount of dollars for these activities at the national, state, and local levels, there is a need to prioritize those dollars and energies that are spent on these activities -- especially in a state like Minnesota with such a large water-resource base. Further, given the expense of restoration activities, typically measured in the hundreds of thousands of dollars per lake, it is wise to protect lake condition whenever possible. Thus, we are proposing a prioritization system that can be applied at a state, basin (watershed), or county level to assist in determining which lakes might be prioritized over others for monitoring, protection, and/or restoration. A decision tree approach was used as a means for conducting the prioritization. In the prioritization scheme the primary emphasis is placed on protecting those lakes which currently have good water quality and monitoring those with inadequate data. A secondary emphasis is on the prioritization of lakes for purposes of restoration. MPCA's ecoregion-based P criteria, in conjunction with Carlson's TSI, served as a primary basis for developing the prioritization. In the overall scheme, lake size was used in the prioritization and, in particular, lakes of 100 acres or more would be of a higher priority for protection, restoration, and/or more extensive monitoring. Other considerations which could be used for further prioritization if data are available (e.g., in a local water plan or watershed district plan) could include: mean depth, watershed size, public access, land use in the shoreline and immediate watershed, and--perhaps most importantly--proposed changes in land use in the watershed. Once lakes are prioritized there must be some likely outcomes or actions to be instituted. A brief discussion of some options is provided. Opportunities to implement these options may vary betweenbasins, watersheds, or counties, depending on available resources.