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Agriculture and Water Quality in the Canadian Great Lakes Basin: I. Representative Agricultural Watersheds¹

ABSTRACT

The 1972 U.S.-Canada Great Lakes Water Quality Agreement established the Pollution from Land Use Activities Reference Group (PLUARG). To meet the objectives of the Pilot Watershed Studies of PLUARG, an approach was developed tbat would allow the quantification of the agricultural component of Great Lakes drainage basin pollution loads. A primary separation of agricultural regions was based on an index of the soil's potential to transfer pollutants to surface and ground water. Agricultural watersheds representative of major soils-crops-livestock combinations were monitored and studied. Selection and preliminary monitoring processes led to 11 sites being monitored for 2 years.

The areas of the 11 study watersheds ranged from 20 to 79 km², of which 22–89% was cultivated, and 0–99% tile-drained. Row-cropped laud, which occupied 10–66% of the watershed areas, was strongly correlated with tile-drained area and fertilizer use. Mean surface-soil clay contents ranged from 7 to 36%. Livestock densities were negligible in some watersheds, but were up to 0.77 animal units ha^–1 in others. Mean precipitation and stream discharge during the study period were approximately 9 and 26% higher, respectively, than expected from long-term means. The proportion of annual precipitation occurring in the January–April period averaged 32%, while approximately 65% of the stream discharge was measured during these 4 months.

Intensive flow-related stream sampling and chemical analyses revealed that the watersheds yielded a wide range of nutrient, sediment, and pesticide loadings to Great Lakes tributaries. The subsequent papers in this series discuss these results and their significance to water quality in the Great Lakes Basin.

Key Words: pollution • runoff • watershed monitoring • stream loadings

¹ Contribution no. 93 of the Land Resource Research Institute, Agriculture Canada, Ottawa, Ontario, K1A 0C6. Research supported by Agriculture Canada, Ontario Ministry of Agriculture and Food, and Ontario Ministry of the Environment as contribution to the International Joint Commission, Pollution from Land Use Activities Reference Group (PLUARG) program.

² Physical Scientist, Land Resource Research Inst.; Biologist, 299 Ferndale, Ave., Ottawa, Ontario, K1Z 6P9, formerly of the Soil Research Inst., Agriculture Canada; Professor, School of Engineering, Univ. of Guelph, Ontario, N1G 2W1; Head of Technical Support, Water Resources Branch, Ontario Ministry of the Environment, Toronto, Ontario, M4V 1P5; and Director, Pesticide Residue Testing Lab., Ontario Ministry of Agriculture and Food, Guelph, Ontario, N1G 2W1; respectively.

Received for publication December 4, 1980.