Challenges in Reducing and Mitigating Nonpoint Source Pollution

Nonpoint source (“NPS”) pollution is generally conveyed from origins which are not easily identified, unconfined, and which are connected to various other sources (EPA 2022). The reduction and mitigation of NPS pollution is, therefore, naturally fraught with a host of difficulties.

In Big Spring Run, Pennsylvania, US, landowners were contacted directly based on NPS load generation areas, and the key challenge of localising NPS sources was resolved by innovative modes of indirectly measuring of sediment and nutrient loss, thus enabling the (ultimately effective) placement of best management practices (“BMPs”) at specific hotspots along Big Spring Run (Fleming et al 2022).

A rising human population within a watershed has often been correlated with declining water quality, leading to a greater need for the reduction and mitigation of NPS pollution. This was undertaken with some success in the case of Roberts Bay (Florida, US) and Newport Bay (California, US) where, by targeting surface waters (which hold nutrients for a much shorter residence time than groundwater), nutrient loads and algal blooms were diminished to a large extent and, making up for the effects of population growth (Green et al 2021).

The installation and implementation of NPS BMPs may interfere with ongoing land use and for that reason meet with resistance by local landowners. This issue was addressed in Cullers Run, West Virginia, US, in a pay-for-performance scheme designed to alleviate nitrate levels in the Potomac River basin, in which fine-scale sampling combined with collaborative and creative community efforts resulted in the creation of a subsurface wetland allowing continued farming operations (Fleming et al 2022).

Given the complexity inherent in socio-ecological systems and their interconnectivity with other meteorological and anthropological phenomena, it is also often not feasible to understand the effects of ramping up practices which demonstrate efficacy on a small temporal and/or spatial scale (Rissman and Carpenter 2015). This calls for, amongst others, the study of reference watersheds or co-monitored watersheds, and sustained long-term monitoring (ideally on the scale of decades) of pre- and post-intervention data points (Rissman and Carpenter 2015).

References:

• Fleming, P.M., Stephenson, K., Collick, A.S., et al. (2022). ‘Targeting for nonpoint source pollution reduction: A synthesis of lessons learned, remaining challenges, and emerging opportunities’. Journal of Environmental Management 308 (2022) 114649. https://doi.org/10.1016/j.jenvman.2022.114649

• Green, L., Magel, C., and Brown, C. (2021). ‘Management pathways for the successful reduction of nonpoint source nutrients in coastal ecosystems’. Reg Stud Mar Sci. 2021 June ; 45: 1–15. doi:10.1016/j.rsma.2021.101851.

• Rissman, A.R. and Carpenter, S.R. (2015). ‘Progress on Nonpoint Pollution: Barriers & Opportunities’. Daedelus 144 (3) Summer 2015. doi:10.1162/DAED_a_00340

• United States Environmental Protection Agency (“EPA”). (2022). ‘Polluted runoff: Nonpoint source pollution’. https://www.epa.gov/nps/basic-information-about-nonpoint-source-nps-pollution