Version 2 2023-10-24, 17:38Version 2 2023-10-24, 17:38
Version 1 2023-10-23, 17:06Version 1 2023-10-23, 17:06
journal contribution
posted on 2023-10-24, 17:38authored byLuwen Wan, Anthony D. Kendall, Sherry L. Martin, Quercus F. Hamlin, David W. Hyndman
Nitrogen and phosphorus pollution is of great concern
to aquatic
life and human well-being. While most of these nutrients are applied
to the landscape, little is known about the complex interplay among
nutrient applications, transport attenuation processes, and coastal
loads. Here, we enhance and apply the Spatially Explicit Nutrient
Source Estimate and Flux model (SENSEflux) to simulate the total annual
nitrogen and phosphorus loads from the US Great Lakes Basin to the
coastline, identify nutrient delivery hotspots, and estimate the relative
contributions of different sources and pathways at a high resolution
(120 m). In addition to in-stream uptake, the main novelty of this
model is that SENSEflux explicitly describes nutrient attenuation
through four distinct pathways that are seldom described jointly in
other models: runoff from tile-drained agricultural fields, overland
runoff, groundwater flow, and septic plumes within groundwater. Our
analysis shows that agricultural sources are dominant for both total
nitrogen (TN) (58%) and total phosphorus (TP) (46%) deliveries to
the Great Lakes. In addition, this study reveals that the surface
pathways (sum of overland flow and tile field drainage) dominate nutrient
delivery, transporting 66% of the TN and 76% of the TP loads to the
US Great Lakes coastline. Importantly, this study provides the first
basin-wide estimates of both nonseptic groundwater (TN: 26%; TP: 5%)
and septic-plume groundwater (TN: 4%; TP: 2%) deliveries of nutrients
to the lakes. This work provides valuable information for environmental
managers to target efforts to reduce nutrient loads to the Great Lakes,
which could be transferred to other regions worldwide that are facing
similar nutrient management challenges.