Stéphane Savary

Assessing the Effects of Historical Land Cover Changes on Runoff and Low Flows Using Remote Sensing and Hydrological Modeling

In some parts of the world, watersheds are experiencing changes in land cover that affect their hydrological regime. This paper presents a methodology to assess the potential hydrological response of the Chaudiere River watershed (Quebec) to historical land cover changes. The objectives of this study are: (1) to determine acceptable and plausible land cover scenarios for the past 30 years based on spatial scenario intercomparison and land cover evolution analyses; and (2) to assess the influence of land cover changes on the hydrological regime of the watershed. Historical land cover changes were assessed from seven optical satellite images using an object-oriented approach. Each scenario was entered into GIBSI, an integrated modeling system. Hydrological simulations showed strong correlations between land cover changes and water discharge at the outlet of the watershed. Results demonstrated a homogeneous effect of land cover on annual runoff. Simulated annual and seasonal low flows were also strongly corr...

Modeling the effects of agricultural BMPs on sediments, nutrients, and water quality of the Beaurivage River watershed (Quebec, Canada)

Agriculture has evolved into the largest non-point source of surface water pollution in Canada as a result of intensification over the past forty years. The Canadian WEBs project (Watershed Evaluation of Beneficial Management Practices, BMPs) was launched to evaluate the environmental and economic performance of BMPs as a means to mitigate agricultural sediment and nutrient issues. In this paper, the Gestion Intégrée des Bassins versant à l’aide d’un Système Informatisé (GIBSI) (or Integrated Watershed Management using a Computer System) integrated modeling framework was used to evaluate the effects of different BMPs on sediment and nutrient yields, as well as water quality in the Beaurivage River watershed in the province of Quebec. A reference scenario was developed that describes the current situation (i.e., base case scenario) of the watershed by calibrating the models used within GIBSI, namely HYDROTEL for hydrology, the Revised Universal Soil Loss Equation (RUSLE) for soil erosion, the Erosion-the Productivity Impact Calculator (EPIC) of the Soil and Water Assessment Tool (SWAT) for contaminant transport and fate, and QUAL2E for stream water quality. The effects of four BMPs were studied: (1) vegetated riparian buffer strips, (2) precision slurry application, (3) grassland conversion of cereal and corn fields, and (4) no-till (on corn fields). Simulation results indicate that BMPs can be effective in reducing nutrient and suspended sediment loads in both surface runoff and stream flow. More specifically, buffer strip and crop rotation showed better efficiency than hog-slurry management and no-till on corn BMPs. Moreover, results highlight the need for further investigation of sediment dynamics in the stream network as well as in the riparian buffer strips.