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Canadian water monitoring program for pesticides

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Overview

Health Canada's Pest Management Regulatory Agency (PMRA) has established a collaborative Canadian Water Monitoring Program for Pesticides (CWMPP).

This program:

Data from the CWMPP will help the PMRA make informed regulatory decisions about pesticides. These data will also allow the PMRA to identify areas where risks to human health and aquatic organisms may be present and requiring further investigation. The results will also support the Government of Canada's commitment under Target 7 of the Kunming-Montreal Global Biodiversity Framework.

Learn more:

The success of this program is thanks to all sampling partners, including federal, provincial, local and Indigenous organizations.

Water monitoring sample collection

Provincial, federal and local partners, including members of Indigenous communities, are working with the PMRA to collect water samples.

These water samples are collected at various locations across Canada from 2 types of water sources:

The location and number of sites where samples are collected may vary year to year as sampling is shifted to address specific issues and program funding changes.

The details of each site sampled can be found on the water monitoring dashboard and the Open Data portal. In some cases where privacy needs to be protected, bounding boxes are used to mask the exact location of the sampling site. A bounding box is defined by coordinates (latitude and longitude) that mark the northwest and southeast corners of a rectangle around a sampling site. To protect privacy, the precise site location is randomly located within the area defined by the bounding box.

Site selection process

The framework for water monitoring programs provides guidance on selecting sampling locations which the PMRA used to develop a site selection process for surface water sites. This process identifies areas in Canada where there is an increased likelihood of detecting pesticides. 

The site selection process includes geomatic analysis of the following:  

IROWC-PEST models the potential movement of pesticides to waterways using several datasets, including: 

This model generates a relative risk index (5 classes, from very low to very high) and highlights areas across Canada that are more prone to pesticides moving to water.

The National Hydro Network (NHN) dataset divides drainage areas across Canada in a consistent and standardized way based on how surface water flows across the landscape.

The most detailed level of drainage (sub-sub drainage areas; SSDAs) are used as working units for the CWMPP site selection. There are 1324 SSDAs across Canada.

The annual crop inventory (ACI) provides information using satellite imaging to identify crops at a spatial scale of 30 meters on an annual basis.

This dataset is used to calculate how much cropland there is in each sampling site catchment area. Cropland includes crop-growing areas, excluding greenhouses (which manage pesticide and water use on-site) and pasture/forage lands (which are categorized separately). This cropland density provides a rough idea of where pesticide applications might be higher, since detailed data on exactly how much pesticide is used, when, and where is not currently available. Because AAFC’s ACI is published with a one-year delay, site selection is based on the most recent available dataset rather than current-year crop conditions. For more information, visit Agriculture and Agri-Food Canada’s Annual Crop Inventory.

Using IROWC-PEST, NHN and ACI the following are calculated for each SSDA:

The individual SSDAs are scored with IROWC-PEST and cropland areas representing 60% and 40% of the score, respectively. The IROWC-PEST is weighted higher because it includes datasets that capture characteristics, such as slope and soil type, which remain constant over time. The cropland proportion is weighted lower because the types of crops grown can vary from year to year.

By using this method, we are able to identify drainage areas with a greater likelihood of pesticide detection. This information allows us to identify areas across Canada where sampling could be prioritized.

The initial ranking results are discussed with each province and/or territory, incorporating local knowledge.

Once priority drainage areas are identified, various other aspects are considered before finalizing sampling site locations, such as:

Based on all information obtained, additional geospatial analysis may be required once potential sampling sites are identified. This follows a process similar to what is described above but for each site catchment area (land area where all water flows into that particular site). This additional analysis can assist in confirming the suitability of potential sampling sites.

The number of sampling sites is ultimately determined by funding. All drainage areas identified as having higher risk for pesticide movement to water may not be included. The CWMPP relies on sampling partners to help maximize program outputs given allocated resources.

For wetlands, the same initial process is used as an indication of potential higher risk areas to initiate discussion with partners. However, it is recognized that the site selection process described above is more suitable for flowing water. Therefore, knowledge and expertise from partners is key to identify sampling locations for wetlands.

For groundwater, wells are selected based on discussions with local hydrogeologists and other provincial and agency experts with local knowledge. To date, wells have been selected based on previous pesticide detections or elevated levels of other chemicals that may indicate risk of groundwater contamination by pesticides. 

For non-agricultural pesticide use, sites are selected to represent areas with a high impact from non-agricultural sources. Selecting these sites relies on extensive local knowledge from partners.

Laboratory analysis

Samples collected are sent to laboratories where they are analyzed, using multi-residue methods, for more than 200 registered pesticides in Canada and some transformation products.

Learn more:

Explore the results

Data generated by the CWMPP is available on our Open Data portal.

You'll find information on:

Our interactive water monitoring for pesticides dashboard can also be useful for summaries of:

Consult the Understanding the Data for data limitations and a disclaimer.

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2025-06-27