Legacy sediment erosion hot spots: A cost-effective approach for targeting water quality improvements

As federal and state governments seek to address nonpoint source (NPS) water pollution, billions of dollars will be spent to implement conservation practices known to reduce sediment and nutrient runoff. Nonpoint source pollution has proven to be a “wicked” challenge for policymakers, characterized by uncertainty and complex interactions among socioeconomic, hydrologic, and other geodynamic systems along multiple dimensions (Shortle and Horan 2017). A recent summary of research indicates, in fact, that the adoption of conventional NPS conservation practices is not directly linked to measurable pollution reduction in most streams in the Chesapeake Bay watershed (Keisman et al. 2018). A primary reason cited for this disconnect is the temporal dynamic by which water quality improvements are delayed or offset by the ongoing effects of legacy pollutants in soils and groundwater (Keisman et al. 2018). (Legacy pollutants are those that remain in the geosphere decades to centuries after the pollution occurred.)Innovative approaches to NPS pollution reduction may be needed to address these legacy pollutants, and thereby meet goals for improved water quality, such as the Chesapeake Bay total maximum daily load (TMDL).