Discerning BMP effectiveness for nutrient reductions in the Mississippi Delta

Author(s): Kröger, R.; Hicks, M.; Prevost, D.; Thornton, K.

There is a significant impetus within the Mississippi River Basin, at both federal and state levels, to determine the possibility and attainability of nutrient reductions. These questions are being asked at several spatial scales, but ultimately are driven toward the largest spatial scale - Gulf of Mexico hypoxia. The Mississippi approach has been to utilize inter-agency collaboration to identify watersheds where BMP nutrient reductions can be demonstrated and to discern the effectiveness of those BMPs. Harris and Porters Bayous are two HUC 10 watersheds where BMPs have been installed on the landscape, and where tiered water quality monitoring with identical sampling frequencies provides a means for quantifying both reductions in nutrient concentrations and loads. Water quality data is being collected at three tiers. The first Tier (edge of field) is being collected by MSU, while Tiers 2 and 3 are being collected by USGS. Nutrient reductions in concentration, 1-year post BMP implementation are discernible at the Tier 1 scale, but are not yet known at Tiers 2 or 3 due to continued data analysis. Monitoring of multiple watersheds provides environmental variables and landscape characteristics that suggest reasons for the observed reductions. These initial answers provide previously unknown information towards improving in state aquatic ecosystem health as well as critically important BMP attainability estimates to inform Gulf of Mexico restoration recommendations.

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