es3c03741_si_001.pdf (3.83 MB)
Important Role of Overland Flows and Tile Field Pathways in Nutrient Transport
journal contributionposted on 2023-10-24, 17:38 authored by Luwen 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.
transport attenuation processesseldom described jointlydominate nutrient deliverynutrient transport nitrogendrained agricultural fields46 %) deliveries2 %) deliveriestile field drainagereduce nutrient loadsfour distinct pathways4 %; tp26 %; tptotal annual nitrogentile field pathwaystotal nitrogentp loadsagricultural sources58 %)5 %)total phosphorussurface pathwaysphosphorus loadscoastal loadswide estimatestransporting 66target effortsstudy revealsstudy providesstream uptakerelative contributionsregions worldwideplume groundwaterphosphorus pollutionoverland flowsoverland flownonseptic groundwatermain noveltyimportant rolehuman wellhigh resolutiongroundwater flowgreat concernfirst basinenvironmental managersdifferent sourcesaquatic lifeanalysis shows