Mitigating lake eutrophication through stakeholder-driven hydrologic modeling of agricultural conservation practices: A case study of Lake Macatawa, Michigan

Authors: LAVORIVSKA, LIDIIA - Syracuse University; Veith, Tameria - Tamie; CIBIN, RAJ - Pennsylvania State University; PREISENDANZ, HEATHER - Pennsylvania State University; STEINMAN, ALAN - Grand Valley State University

Submitted to: Journal of Great Lakes Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2021
Publication Date: 10/28/2021
Citation: Lavorivska, L., Veith, T.L., Cibin, R., Preisendanz, H.E., Steinman, A.D. 2021. Mitigating lake eutrophication through stakeholder-driven hydrologic modeling of agricultural conservation practices: A case study of Lake Macatawa, Michigan. Journal of Great Lakes Research. 47(6):1710-1725. https://doi.org/10.1016/j.jglr.2021.10.001.
DOI: https://doi.org/10.1016/j.jglr.2021.10.001

Interpretive Summary: Lake Macatawa, which flows into Lake Michigan, often contains high levels of total phosphorus. Local stakeholders are interesting in understanding the origin of where the excess phosphorus comes from and determine possible ways for reducing it without negatively impacting the surrounding agricultural production. We worked with the stakeholders to create a watershed model that represented baseline management and landuse conditions and to vailidate that model with existing measured data. Additionally, we evaluated the impacts of several a number of scenarios of interest to stakeholders to determine which agricultural management practice changes would most reduce total phosphorus into the lake. We found total phosphorus from the agricultural lands could be substantially reduced by widespread adoption of continuous no-till, cover crops, and filter strips across the watershed's crop fields and by converting some of the low yield crop fields into continuous grasslands. By using detailed management information from the watershed stakeholders within a process-based water quality model, this study provides some potential solution scenarios releaveant to other small agricultural watersheds with high soil P levels in the Great Lakes Region.

Technical Abstract: Lake Macatawa is a hypereutrophic water body that connects with Lake Michigan via a navigation channel. Excess phosphorus (P) concentrations have resulted in a Total Maximum Daily Load (TMDL) for total phosphorus (TP) in the lake, which has not been met. To guide land management and water pollution control in the Macatawa watershed, a Soil and Water Assessment Tool (SWAT) model and scenarios of agricultural best management practices (BMPs) were developed in consultation with stakeholders. Modelling emphasized incorporating practices representative of local agricultural conditions. Approaches to initializing high legacy soil P levels in SWAT were tested. The validated model was used to evaluate the influence of BMPs on lake water quality and identify which practices are necessary for meeting the TMDL. The model showed that eliminating manure applications would have small effect on curbing TP loading, but continuous no-till and high residue combined with already used subsurface manure application would yield notable TP reductions. Achieving TMDL-mandated TP reduction of 72% is possible through a widespread adoption of multiple BMPs (continuous no-till with high residue, cover crops, filter strips, and conversion of some marginal croplands to perennial grasses) across all the watershed’s row croplands. The study highlights how guidance from a local community interested in watershed improvement was integrated with modeling towards addressing eutrophication with informed watershed management. The Lake Macatawa case study presents a tractable system from which management solutions could be transferred to similar small agricultural tile-drained watersheds with high legacy soil P levels in Great Lakes.