Research Project Updates

Non-point source agricultural contamination (phosphorus and nitrogen) is a serious concern for surface and groundwater quality within the Great Lakes Basin (GLB), with severe associated environmental and ecological implications. The roles of groundwater-surface water interactions and movement of stream sediments in nutrient transport in agriculturally-dominated areas are currently not well understood. The purpose of this research is therefore to investigate the spatial and temporal evolution of phosphorus and nitrate in various hydrological pathways and stream sediments in a typical clay plain system in the GLB.

This research aims to use field-based data collection to help to fill the knowledge gaps that exist concerning nutrient transport through the surface water and groundwater interfaces and the hydrogeological processes influencing this transport in clay dominated settings, typical of the GLB. The subsequent research objectives are to:

1. Characterize the spatial distribution and temporal evolution of P and N in the shallow groundwater/streambank, stream and streambed over multiple growing seasons;

2. Relate the observed concentrations to watershed characteristics (e.g. land use) and hydrological patterns;

3. Model the effect of future changes in hydrologic regime and agricultural practice on the spatiotemporal distribution of stream/streambed P; and

4. Develop a conceptual model of the geological and hydrological factors responsible for the transport and fate of agricultural P and N to GLB tributaries (via groundwater discharge, overland flow, tile flow) in a typical clay plain setting.

Monthly collection of water (groundwater, surface water, tile water, and hyporheic water) and sediments for water quality analyses (primarily phosphorus and nitrogen species) from five study sites throughout the watershed is conducted. Field research (water and sediment sample collection) and mathematical modelling will continue to be performed to investigate contaminant inflows/transport through the groundwater-surface water interface and determine how the contaminated sediments move downstream in order to better understand processes that contribute to contamination of GLB tributaries by nutrients in agricultural subcatchments.

Thus far, project results suggest that tile drainage water and surface runoff are the main transport pathways for agricultural nutrients in the watershed, with varying influence on surface water quality throughout the year. Groundwater is likely not a significant source of nutrients of to the stream due to clay-rich soil and abundant tile drainage systems in the watershed. Instream loading of phosphorus from streambed sediment may have a critical impact on water quality in the summer months. Further monitoring of this nutrient delivery mechanism is essential to understand overall nutrient transport dynamics in the watershed.

Best management practices (BMPs), such as conservation tillage practices, in the watershed have been linked to water quality observations, particularly elevated dissolved phosphorus concentrations, in the stream. Consequently, BMPs in the watershed should be refined to improve water quality in the area.

Provincial agricultural and environment ministries (OMAFRA, MECP) will benefit from the project results for the development of future research directions or policies for water resource protection related to impacts of agricultural practices. Ontario conservation authorities and landowners in the area can integrate the new knowledge in watershed conservation, restoration, and best management practices.