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 Chaudière River watershed (Québec) to historical land cover changes. The objectives of this study are: (1) to determine acceptable and plausible land cover scenarios for the past 30years 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 correlated to agricultural and forested land cover changes. Globally, results corroborate that land cover constitutes a governing factor of watershed hydrology in the Chaudière River watershed.