Advancing watershed nitrogen management at the local level
Background information:
- Coastal watersheds are increasingly managed to reduce nitrogen (N) loading from non-point sources, such as septic systems and fertilizers.
- Land use managers rarely have the ability to compare N loading potential of different land management options to guide their decisions.
- We developed "N-Sink" – a simple, GIS-based decision support tool – to help prioritize N management, land conservation and resource restoration activities at the watershed scale to reduce N loading to coastal waters.
Our approach:
N-Sink uses widely available GIS tools to map flow paths from N sources to watershed outlets. As N-laden water moves through the watershed, cumulative N removal estimates are calculated through the interception of landscape N sinks (riparian wetlands, ponds/lakes/reservoirs and stream reaches). Retention time of the N-laden water is a critical component of N sink effectiveness as it moves across the landscape. We used published studies to develop equations that estimate %N removal of each sink type and widely available GIS data to extract relevant physical characteristics of landscape sinks, such as drainage area to a pond or stream reach, reach length, pond size and riparian wetland width. N-Sink has the interactive capability that allows the user to identify proposed N source areas as well as static maps depicting N loading potential across a watershed as high, medium or low, based on N sink locations and removal effectiveness. N-Sink can compare the N loading potential of, for example, proposed locations for residential development, lands under consideration for protection or restoration, or source areas under consideration for N source reduction measures.
Progress:
Work is underway to gather input from users, including NEMO programs, land use managers, planners and land conservation/restoration organizations, to optimize the user interface for easy navigation and comprehension. This N-Sink tool will enhance the ability of coastal land use managers to effectively manage land for watershed N.
Other Resources:
Demo of N-Sink tool (pdf)
DRAFT Guidance Document (pdf)
