Hydrological responses of a watershed to historical land use evolution and future land use scenarios under climate change conditions

摘要

Watershed runoff is closely related to land use but this influence isdifficult to quantify. This study focused on the Chaudière Riverwatershed (Québec, Canada) and had two objectives: (i) to quantify theinfluence of historical agricultural land use evolution on watershed runoff;and (ii) to assess the effect of future land use evolution scenarios underclimate change conditions (CC). To achieve this, we used the integratedmodeling system GIBSI. Past land use evolution was constructed usingsatellite images that were integrated into GIBSI. The general trend was anincrease of agricultural land in the 80's, a slight decrease in thebeginning of the 90's and a steady state over the last ten years.Simulations showed strong correlations between land use evolution and waterdischarge at the watershed outlet. For the prospective approach, we firstassessed the effect of CC and then defined two opposite land use evolutionscenarios for the horizon 2025 based on two different trends: agricultureintensification and sustainable development. Simulations led to a wide rangeof results depending on the climatologic models and gas emission scenariosconsidered, varying from a decrease to an increase of annual and monthlywater discharge. In this context, the two land use scenarios inducedopposite effects on water discharge and low flow sequences, especiallyduring the growing season. However, due to the large uncertainty linked toCC simulations, it is difficult to conclude that one land use scenarioprovides a better adaptation to CC than another. Nevertheless, this studyshows that land use is a key factor that has to be taken into account whenpredicting potential future hydrological responses of a watershed.