Groundwater contribution to stream nutrient quality in a clay dominated agricultural watershed in the Lake Huron Basin

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

Dans les comptes rendus d’articles de la conférence: GeoNiagara 2021: 74th Canadian Geotechnical Conference; 14th joint with IAH-CNC

ABSTRACT: Surface water quality in agricultural watersheds represents a combination of contributing water sources (e.g. groundwater flow, surface runoff, subsurface tile discharge) and reflects hydrogeologic character and land management strategies. Pairwise concentrations of surface water and groundwater quality data can be used to understand the potential contribution of groundwater to streams under varying flow conditions. Research is conducted in the Upper Parkhill Watershed, located within the Lake Huron basin and in the jurisdiction of the Ausable Bayfield Conservation Authority. The area is characterized by heavy clay soils and extensive agricultural land use. Parkhill Creek is the main watercourse and features an Integrated Groundwater and Surface Water Monitoring station managed by the Ontario Ministry of the Environment, Conservation and Parks (MECP) at the watershed outlet. Discrete sampling methods are used to monitor surface water and groundwater concentrations of phosphorus and nitrogen at the watershed outlet and five upstream locations. Surface water and groundwater levels are continually monitored, and water quality samples are collected on monthly and storm-event basis over one year period. Preliminary water quality data indicated that from July 2020 to April 2021, concentrations of TP and DRP in the surface water have ranged from 0.01-0.54 mg/L and <0.03-0.26 mg/L, respectively. Groundwater DRP values are typically under the detection limit, except for a concentration of 0.14 mg/L observed in a shallow well in September and DRP concentrations exceeding 0.1 mg/L in all shallow wells in April. Nitrate-N values range from 0.15-13.80 mg/L in the surface water and 0.06-3.76 mg/L in the groundwater during this period. Preliminary analysis indicates that groundwater discharge does not significantly contribute nutrients to Parkhill Creek. Alternative transportation pathways (e.g. artificial tile drainage) and within stream sources (e.g. streambed sediment) may have a greater influence on stream water quality in agricultural clay dominated settings.

Please include this code when submitting a data update: GEO2021_406

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