Investigating relationships between climate controls and nutrient flux in surface waters, sediments, and subsurface pathways in an agricultural clay catchment of the Great Lakes Basin

Hannah May; Sarah Rixon; Scott Gardner; Pradeep Goel; Jana Levison; Andrew Binns

doi:10.1016/j.scitotenv.2022.160979

Investigating relationships between climate controls and nutrient flux in surface waters, sediments, and subsurface pathways in an agricultural clay catchment of the Great Lakes Basin

Sci Total Environ. 2023 Mar 15:864:160979. doi: 10.1016/j.scitotenv.2022.160979. Epub 2022 Dec 20.

Authors

Hannah May¹, Sarah Rixon², Scott Gardner², Pradeep Goel³, Jana Levison², Andrew Binns²

Affiliations

¹ School of Engineering, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada. Electronic address: hmay@uoguelph.ca.
² School of Engineering, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
³ Ministry of the Environment, Conservation and Parks (MECP), Etobicoke, Ontario, Canada.

PMID: 36549520
DOI: 10.1016/j.scitotenv.2022.160979

Abstract

Water quality within agricultural catchments is governed by management practices and climate conditions that control the transport, storage, and exchange of nutrients between components of the hydrologic cycle. This study aims to improve knowledge of nitrogen (N) and phosphorus (P) transport in low permeability agricultural watersheds by considering spatial and temporal trends of surface water nutrient concentrations in relation to hydroclimatic drivers, sediment quality, shallow hyporheic exchange, groundwater quality, and tile drain discharge over a 14-month field study in a clay hydrosystem of the Lake Huron basin, one of the five Great Lakes. Results found that events of varying magnitude and intensity enhanced nutrient release from overland flow and subsurface pathways. Tile drain discharge was found to be a consistent and elevated source of P and N to surface waters when flowing, mobilizing both diffuse nutrients from fertilizer application and legacy stores in the vadose zone. Surface water quality was temporally variable at the seasonal and event scale. Targeted sampling following fertilization periods, snowmelt, and moderate precipitation events revealed catchment wide elevated nutrient concentrations, emphasizing the need for targeted sampling regimes. Controls other than discharge magnitude and overland flow were found to contribute to peak nutrient concentrations, including internal nitrate loading, soil-snowmelt interaction, catchment wetness, and freeze thaw cycles. Sediments were found to store P in calcium minerals and have a high P storage capacity. Instream mechanisms such as sediment P fixation and hyporheic exchange may play a role in mediating surface water quality, but currently have no discernable benefit to year-round surface water nutrient concentrations. Best management practices need to focus on reducing sources of agricultural nutrients (e.g., field phosphorus concentrations and tile drain discharge loading) at the watershed scale to reduce nutrient concentrations and export in flashy clay catchments.

Keywords: Agriculture; Climate; Nitrogen; Phosphorus; Sediments; Watershed.