GeoBase in Action
National Hydro Network (NHN) and Canadian Digital Elevation Data (CDED) contribute to measuring Risk of Water Contamination Indicators
Recently, Agriculture and Agri-Food Canada (AAFC) initiated the development of agri-environmental indicators to measure the efficiency of agricultural management practices and to provide an objective, science-based assessment of environmental sustainability. Indicators to measure the risk of water contamination by phosphorus and coliforms were developed using an index approach. This approach enables the integration of data on source contamination, contamination transport, and the factors connecting source contamination and transport.
One important factor connecting agricultural land and water bodies is the measure of saturation excess runoff. Saturation excess runoff is the point at which runoff will occur once the soil is so saturated that it can no longer hold water. Total rainfall amount and landscape factors such as soil depth (i.e., available water storage capacity), upland-watershed area, and local topography are the factors determining whether or not a particular area in a watershed will generate runoff. To evaluate this, a Topographic Index (TI) was computed for all agriculturally classified watersheds in Canada using the GeoBase CDED and NHN data.
The Outcome
The project was successful since it provided the risk indicators with a connectivity factor representing the propensity of developing runoff on agricultural land.
Results show that the highest TI values are found in regions where topography tends to be hilly and where agriculture is primarily located in river valleys. The lowest values are found in flat areas with little flow convergence. In the Prairies, localized high TI values are found where agriculture is found close to important water bodies such as lakes or major rivers.
A detailed article describing this work is available in PDF format.