Impact of land-use changes on the hydrological processes in the Elbow river watershed in southern Alberta

Due to the rapid population growth and urbanization in the City of Calgary, the Elbow River watershed in southern Alberta covering 1238 km has been subjected to considerable land-use changes over the last decade. The objective of this study is to assess the impact of land-use intensification simulated with a cellular automata (CA) model on the hydrological processes of the watershed using MIKE-SHE, a physically-based and distributed hydrological model. MIKE-SHE was calibrated for the period 1985-1990 and validated for the period 2000-2005. The calibration was achieved by comparing observed and simulated flow data. The CA model was calibrated using four land-use maps covering the period 1985-2001 and validated against the map of 2006. It was then used to forecast land-use changes over the period 2006-2031 at a five-year interval. Land-use based watershed characteristics were extracted from these simulated maps and transferred to MIKE-SHE to assess the impact on the hydrological processes in the watershed. Results of calibration and validation showed sufficient model performance. The total water balance error for all MIKE-SHE model runs was less than 1% of the total precipitation. Simulations carried out between 2001 and 2031 showed a 25% increase in urbanization (corresponding to 5% of the watershed area) in the watershed which resulted in a 2.6% increase in overland flow (OL), 2.3% reduction in evapotranspiration (ET), and a 11% increase of combined overland and base flow into the river flow.