SPARROW (SPAtially Referenced Regression On Watershed attributes) is a watershed model that relates patterns in water quality to human activities and natural processes. Using existing monitoring data, SPARROW analyses the water quality of streams, rivers, and lakes in relation to the location and relative intensity of contaminant sources, landscape characteristics, and environmental factors. This means that SPARROW models can follow the transport of modelled contaminants and nutrients from inland watersheds downstream to larger water bodies, keeping track of their origins and fates.

SPARROW - SPARROW model - Figure 1
Figure 1 - Graphic displaying how the SPARROW model analyzes the impacts of contaminant sources on water quality. Credit: Grabhorn Studios


This can give insight on the causes and effects of challenging and complex environmental issues related to water quality. One such issue found across the transboundary basins is excessive nutrient loading. Human land use practices and activities, like agriculture and wastewater discharge, are compounding the total amounts of nitrogen (TN) and phosphorus (TP) that enter the boundary waters. These are both examples of constituents that SPARROW models can track as they are transported and deposited into receiving lakes or reservoirs.

In excess, these nutrients can become a major problem for water quality. Excessive nutrient loading can cause algal blooms that can be toxic to humans and wildlife, increase the costs of treating drinking water, and limit recreational activities. This nutrient over-enrichment can also lead to eutrophication in downstream waterbodies, which depletes them of oxygen, consequently threatening fish and the overall health of aquatic ecosystems. Examples of lakes that have become eutrophic because of excess binational nutrient loading include: Lake Champlain-Missisquoi Bay (IJC, 2012a), Lake Erie (IJC, 2014a), Lake of the Woods (Clarke and Sellers, 2014) and Lake Winnipeg (Environment Canada and Manitoba Water Stewardship, 2011).

Issues of water quality have broad effects and are very pertinent to the IJC. The Boundary Waters Treaty, which established the IJC in 1909, provides principles for Canada and the United States to follow in using the waters they share. Far ahead of its time, the treaty states that waters shall not be polluted on either side of the boundary to the detriment of health or property on the other side. This applies to boundary water systems as a whole as well as the many IJC Boards including the Red River, the Souris River, and the Rainy-Lake of the Woods boards that have language in their directives to address issues of water quality. Furthermore, since the early 1970s, through the Great Lakes Water Quality Agreement, Canada and the United States have made it a goal to restore and maintain the physical, chemical, and biological integrity of the Great Lakes. To help achieve these goals and address issues of water quality across the transboundary, nutrient reduction strategies are needed that require knowledge of where water quality problems exist, as well as where and from what sources the contributing nutrients originate throughout the watershed. Through applications like SPARROW, modelling helps provide answers to these questions.

Normally, water quality health is determined through water quality monitoring, defined as the sampling and analysis of water and conditions of the waterbody (i.e. a stream, lake, river, or estuary). It evaluates the physical, chemical, and biological characteristics of a water body related to human health, ecological conditions, and designated water uses in the waterbody (US Environmental Protection Agency). Models on the other hand are tools for interpreting such observations. For example, using geographic data models can simulate patterns using both statistical relationships and physical processes represented in the model to develop a more complete picture of water quality issues in a watershed. These findings can be mapped in GIS software. The integration of monitoring and modelling is crucial for our current and future understanding and management of large-scale water quality.

SPARROW modelling results can help:  

  • Determine how to reduce loads of contaminants and design protection strategies;
  • Design strategies to meet regulatory requirements;
  • Predict changes in water quality that might result from management actions; and
  • Identify gaps and priorities in monitoring.

The output of SPARROW models is a spatial representation of total nutrient load and yield, broken down by watershed. In addition, the model can produce a breakdown of the different sources of these nutrients ranging from human activities and land use practices, to environmental sources including agricultural activity, atmospheric deposition, and more.

This data can be explored using Interactive Mappers. Through these mappers, the relationships between contaminant transport, human activities, and natural processes can be visualised through an interactive map and nutrient source charts. They also act as a location to download the model data and results from the SPARROW model.


A map created displaying Total Phosphorous by sub-watershed of the Red-Assiniboine drainage area using mapper data and a screenshot comparing sources of phosphorous in the Red-Assiniboine mapper
Figure 2 – A map created displaying Total Phosphorous by sub-watershed of the Red-Assiniboine drainage area using mapper data and a screenshot comparing sources of phosphorous in the Red-Assiniboine mapper