Watershed Evaluation of Beneficial Management Practices Approach
The Watershed Evaluation of Beneficial Management Practices (WEBs) program assessed the environmental and economic performance of selected agricultural beneficial management practices (BMPs) at nine small watershed sites (approximately 300-2,500 hectares each) across Canada. A watershed is an area of land from which all runoff drains into the same water body. And BMPs are farming practices designed to minimize negative impacts on the environment. Water quality degradation caused by excessive sediment and nutrient runoff can be a critical environmental impact in agricultural watersheds.
What did the Watershed Evaluation of Beneficial Management Practices Program study?
A suite of BMPs was applied at each of the nine WEBs watershed research sites. Each site has unique landscapes, climates, agricultural practices, and complex socio-economic and agri-environmental issues. BMPs and research methods were selected to address these local and regional issues. Not all BMPs are appropriate for all regions. For example, diversion terraces are a common practice in New Brunswick’s hilly potato belt, but are not needed in a flat Prairie landscape. As a result, WEBs did not test the effect of all BMPs across different landscapes, and the suite of BMPs was different at each project site. However, some BMPs may be applicable in multiple regions. Since the BMP may perform differently in each landscape or climate zone, WEBs researchers studied these BMPs in more than one location. For example, fencing to exclude cattle from waterways was studied in four WEBs watersheds; but study methods and results varied at each site.
A unique aspect of the WEBs program was the implementation of multiple BMPs in each watershed. WEBs researchers looked at individual BMP performance as well as the cumulative impact of multiple BMPs at the watershed scale. In some cases, one BMP might be enough; in other situations, a suite of BMPs may be needed to address the issue in question.
Each of the WEBs watershed studies included the following components:
- Biophysical evaluations measured the environmental impact of BMPs.
- Economic evaluations examined the costs and benefits of implementing BMPs.
- Hydrologic modelling input data from the biophysical component into computer software to assess how nutrients and sediments are transported from agricultural land and the impact of these transport processes on BMP performance. Scaling up uses computer modelling to extrapolate findings to intermediate and regional watershed levels.
Integrated modelling combined hydrologic and economic considerations into a decision-support tool for long-term watershed planning. Integrated modelling frameworks were created for two WEBs project sites (Manitoba and Quebec), and other WEBs sites included this approach in their analyses.
WEBs biophysical researchers used various scientific methods to measure the impact of BMPs on water quality and other environmental parameters such as soil or riparian health. Methods included historic benchmarking, paired watersheds, upstream and downstream monitoring, and edge-of-field testing.
WEBs research primarily focused on assessing the effect of BMPs on water quality. Other indicators of environmental health – such as soil or riparian health, biodiversity and greenhouse gas emissions – were also examined at several WEBs watershed sites.
Water quality was assessed in WEBs using a minimum set of standard chemical and physical parameters. Sampling occurred at a sufficient frequency to track water quality changes. At some sites, sources of contaminants in water, and the movement of contaminants between the field and the stream, were studied. And at most WEBs sites, water quality samples were taken at the watershed outlet to identify any cumulative impacts of BMP implementation.
Economic research can provide producers with credible estimates of the on-farm costs and benefits of BMPs, so that they can make informed choices about implementing them. Knowledge of the on-farm and societal costs and benefits of BMP adoption, and a greater understanding of producer attitudes and impediments to adoption, can help governments to develop policies or programs that encourage the adoption of effective BMPs.
Economists at all nine WEBs watersheds used a variety of analytical approaches to estimate the on-farm costs of implementing BMPs and potential on-farm and off-farm benefits. These methods reflect the diversity of factors affecting each watershed and included:
- Econometric analysis of farmers' likelihood of adopting BMPs
- Enterprise farm budgets to determine net income at the enterprise level
- Financial models to generate financial statements for farm businesses
- Optimization models to determine the best allocation of farm resources
- Whole-farm analysis of the impact of BMP adoption on total farm income and financial performance
In some watersheds, the BMP assessments were conducted on a single farm unit. In others, economists developed representative farm types and sizes to reflect typical farms in the watershed.
More extensive economic assessments were undertaken as part of two integrated economic-hydrologic modelling projects at the South Tobacco Creek (Manitoba) and Bras d'Henri (Quebec) WEBs sites. At these two sites, economic assessments were conducted at both the small watershed scale and at the larger, encompassing watershed scale.
A hydrologic model is computer software that simulates a watershed's surface water and groundwater runoff responses to precipitation and human stresses. It represents the watershed through an interconnected system of hydrologic components that reflect the properties and movement of water and solutes in the watershed. The Soil and Water Assessment Tool (SWAT) has been the primary hydrologic model used in most WEBs watersheds.
Hydrologic modelling at each WEBs site complemented the biophysical evaluation by simulating watershed hydrology and water quality and by using the models to evaluate BMP effectiveness. The models also allowed for scaling-up of biophysical information gathered from the micro-watershed and edge-of-field levels to the next-level watershed to provide a regional perspective.
Climate, topography, soil, vegetation and land-use data collected from within the WEBs watersheds were used to validate the models. WEBs researchers enhanced their models as required by adding modules to depict watershed- or BMP-specific physical processes or to suit Canadian climatic conditions. The complexity of the models varied between the nine WEBs watersheds based on agronomic practices and watershed characteristics.
Integrated modelling helps extrapolate both the water quality and economic impacts (costs and benefits) of implementing individual BMPs or suites of BMPs at various locations and intensities throughout a watershed. This method of extrapolating results is needed to better understand and predict the costs, benefits and environmental impacts of applying BMPs over larger areas and for longer time periods. This includes predicting where in the landscape a BMP is likely to have the greatest effect. Integrated models can also help policy and program decision makers identify effective financial or regulatory incentives to encourage producers to adopt BMPs.
Integrated modelling projects were initiated at two of the WEBs sites - South Tobacco Creek (Manitoba) and Bras d'Henri (Quebec). Extensive hydrologic and economic assessments were conducted at the two sites to provide data for the integrated models. Economic models estimated costs for specific BMPs or combinations of BMPs at the farm and watershed level, while the watershed hydrologic model simulated BMP impact on water quality.
WEBs research has resulted in the publication of over 60 scientific papers and several fact sheets. These products can be viewed on our Communications page.
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