Landscape and local factors influence water purification in the Monteregian agroecosystem in Québec, Canada

The management of riparian areas in agricultural regions is important for the protection of water quality. In Quebec, a buffer strip of at least three meters width is required for riparian buffers adjacent to agricultural areas. However, other qualities of the riparian area and the surrounding landscape may affect the ability of a system to deliver a water purification ecosystem service. This study, located in a tile-drained agroecosystem in the Monteregie (Quebec, Canada), aims to unravel the importance of local factors (the environment adjacent to the stream) and landscape factors (the environment in the whole drainage basin) in water purification through sediment and nutrient retention. We assessed riparian and water quality in twenty-one sites distributed among four headwater streams. A regression analysis indicates that both landscape and local variables influence the provision of water purification. We therefore suggest that the effect of riparian buffers might be mediated by other factors such as subsurface drainage or local land management. Landscape configuration (the geometry and location of various land uses) was identified as playing a key role in the level of ecosystem services provided. We suggest that management of water quality in agroecosystems should focus both on buffer strips and on management of larger source areas in the basin. Interventions should not be only limited to recommendations for buffer width, but should also consider interactions between other local and landscape factors.