Proposed WCR Statewide Phosphorus Standard UAA


Project Description: Current monitoring data indicates that the phosphorus criteria proposed for state-wide application to wadable streams will be exceeded in some watersheds not significantly impacted by human activities. This is due to natural sources of phosphorus both in the groundwater and in surface water runoff. These sources are functions of bedrock geology, soil type and slope and are unrelated to land use or human activity. Unless a way is found to adjust the criteria for these natural factors, phosphorus standards will be applied to streams that cannot be met regardless of BMP adoption rates. In these situations individual use attainability analyses will be required to remove them from the impaired list. The goal of this project is fund an LTE or contract with UWSP to review existing data sources including NonLTT data and other DNR data sets to characterize the geographic distribution of groundwater phosphorus to wadable streams. This proposal uses existing data collected as part of the DNR non-long term trend site network and other sources to augment the work of Paper 1722 and develop a mechanism for implementing statewide phosphorus standards that recognize natural phosphorus sources.


Project Justification: The goal is to normalize the TP relationship for groundwater, soil type & slope such that more of the relationship between land use and TP can be explained. If the observed TP values in non-agricultural watersheds can be explained in this fashion, it creates the possibility of adjusting the entire TP land use gradient line to estimate the “Best Attainable Condition”. This evaluation will begin development of the database that will be necessary for the dozens of individual UAA studies that will be necessary for implementing the proposed phosphorus standard.


Activity Code: Use Attainability Analysis Analysis of this data will describe relationships among the contributing variables. Follow-up work could include identification of watersheds as candidates for “Best Attainable Condition” along the land use gradient and characterization of the degree of adoption of best management practices in those watersheds. The dataset could be enlarged by winter sampling of the 240 sites that contributed to Paper 1722.

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