To determine the hydrological impact of a large-scale mountain pine beetle (abbreviated as MPB) infestation on the Upper Elbow River watershed, a hydrological model was created and calibrated using a dataset from Alberta Environment over the years 2003 - 2005. The root mean squared error of the flow was approximately 10.6 m3/s. The greatest error occurred in Jun 2005 where a much higher amount of precipitation than the previous two years was recorded. An MPB model was used to simulate an epidemic infestation. Various different scenarios were attempted, but the increase in the water yield of the Elbow River watershed could not be confirmed.