Effectiveness of Best Management Practices to Reduce Phosphorus Loading to a Highly Eutrophic Lake

Abstract

Reducing nonpoint source pollution is an ongoing challenge in watersheds throughout the world. Implementation of best management practices, both structural and nonstructural, is the usual response to this challenge, with the presumption that they are effective. However, monitoring of their efficacy is not a standard practice. In this study, we evaluate the effectiveness of two wetland restoration projects, designed to handle runoff during high flow events and serve as flow-through retention basins before returning flow further downstream. The Macatawa Watershed is located in west Michigan, is heavily agricultural, and drains into Lake Macatawa, a hypereutrophic lake with total phosphorus concentrations usually exceeding 100 µg/L. We measured turbidity, total phosphorus, and soluble reactive phosphorus both upstream and downstream of these wetland complexes during base flow and storm events. While both turbidity and phosphorus increased significantly during storm events compared to baseflow, we found no significant difference in upstream vs. downstream water quality two years following BMP construction. We also measured water quality in Lake Macatawa, and found the lake remained highly impaired. Possible reasons for the lack of improved water quality: (1) The restored wetlands are too young to function optimally in sediment and phosphorus retention; (2) the scale of these BMPs is too small given the overall loads; (3) the locations of these BMPs are not optimal in terms of pollutant reduction; and (4) the years following postconstruction were relatively dry so the wetlands had limited opportunity to retain pollutants. These possibilities are evaluated.

Best Management Practices for Diffuse Nutrient Pollution: Wicked Problems Across Urban and Agricultural Watersheds

“…Nutrient removal by BMPs may diminish when installed in nonoptimal locations, , as evidenced by tile-drained flows bypassing agricultural BMPs . Some studies suggest placing BMPs in critical source areas, which are areas with land uses that tend to generate pollutants and/or high hydrologic connectivity to sensitive receiving waters. − Indeed, a study by Du et al in the Liu River Watershed in China found that implementing conservation tillage and installing vegetated filters in critical source areas successfully reduced TN and TP loads in a small agricultural watershed.…”

“…However, it should be noted that several studies have also identified little relationship between inflow nutrient concentrations and outflow nutrient concentrations from structural BMPs. , The sensitivity of BMP performance to inflow volumes and pollutant loads indicates that appropriate sizing of the BMP is a key factor affecting BMP nutrient removal performance. Indeed, there are instances where BMP function at the watershed scale is not as intended due to under-sizing of the BMP. , For example, an undersized stormwater bioretention basin in North Carolina resulted in a 10% reduction in TP, compared to 44% in the correctly sized basins . Future research on the collective impacts of seasonal variations, storm intensity and size, and influence of concentrations on BMP performance is necessary.…”

“…Nutrient removal by BMPs may diminish when installed in nonoptimal locations, 91,92 as evidenced by tile-drained flows bypassing agricultural BMPs. 93 Some studies suggest placing BMPs in critical source areas, which are areas with land uses that tend to generate pollutants and/or high hydrologic connectivity to sensitive receiving waters.…”

Evaluating suspended sediment and turbidity reduction projects in a glacially conditioned catchment through dynamic regression and fluvial process‐based modelling

“…These impacts motivate water resources and land use managers to employ fluvial sediment management strategies, but the implementation of these strategies can be difficult. Challenges related to effective management include identifying source conditions of impairments (Giri et al, 2012; Hanief & Laursen, 2019), siting best management practices (BMPs) in the watershed (Himanshu et al, 2019; Qiu et al, 2018; Steinman et al, 2018; Strauch et al, 2013), quantifying the effectiveness of existing BMPs (Bishop et al, 2005; Engebretsen et al, 2019), and evaluating new BMPs for future climate scenarios (Jeon et al, 2018). BMP selection also needs to be tailored to the physiographic properties of the system under consideration.…”

‘Get a Fish’ vs. ‘Get a Fishing Skill’: Farmers’ Preferred Compensation Methods to Control Agricultural Nonpoint Source Pollution

“…Non-engineering means mainly include the development of environmental regulations, fertilizer and nutrient management systems, and integrated pest management techniques [7,8]. Although these methods have achieved positive outcomes, they have been limited by certain issues [10,11]. The most prominent challenge is that farmers lack the willingness to voluntarily participate in these practices [12].…”