Identifying how to reduce phosphorus loads from Lake Erie agricultural tributaries

Session: 41a. - Great Lakes Harmful Algal Blooms Research from Watershed Influence to Ecosystem Effects

Laura Johnson, Heidelberg University, National Ctr for Water Quality Res., [email protected]
Jakob Boehler, Heidelberg University, NCWQR, [email protected]
Remegio Confesor, Heidelberg College, NCWQR, [email protected]

Abstract

In the Western Lake Erie Basin, the current strategy to reduce phosphorus exports from agricultural lands is to target hotspots in the watershed that are a major source of dissolved reactive P (DRP) runoff. Yet, increasing evidence suggests we instead need a basin-wide management change because a majority of farms are leaking a moderate amount of DRP. For this study, we aimed to clarify which strategy would be most appropriate to effectively decrease the DRP loadings to Lake Erie by monitoring water quality during storm events from 10 subwatersheds of the Sandusky and Maumee Rivers.  Our results suggest that chemographs were almost identical across all of the subwatersheds for each of the 5 monitored storm events during 2016 and 2017. Rising and falling limbs were similarly timed and peak DRP concentrations ranged from 0.10 – 0.25 mg/L.  Peak concentrations were lower in the subwatershed with remnant forested land during one of the late spring 2016 events.  These results imply it’s the common row-crop agricultural practices leading to DRP losses rather than the actions of a few bad actors.

1. Keyword
nutrients

2. Keyword
phosphorus

3. Keyword
watersheds