Indicator of risk of water contamination by phosphorus: Temporal trends for the Province of Quebec from 1981 to 2001

Abstract

An indicator of risk of water contamination by phosphorus (IROWC-P) was developed to estimate the risk of phosphorus (P) contamination in water by agriculture, and to evaluate how this risk changes over time based on the census data obtained every 5 yr. For the province of Quebec, IROWC-P is calculated with census data from 1981, 1986, 1991, 1996 and 2001. In 2001, 85% of the Soil Landscapes of Canada (SLC) agricultural polygons of Quebec were in the low and moderate risk classes and the remaining 15% in the high risk class. Although agricultural production statistics show marked changes from 1981 to 2001 in livestock herd composition, area under cultivation, agricultural land use and use of inorganic phosphorus fertilizer and animal manure, no trend was observed in the estimated risk over the same period. Increased risk of P transport from agricultural fields to water is expected when agricultural soils are rich in P or have excess P relative to crop needs and have a high potential for soil erosion and surface runoff.