Water allocation under changing natural and anthropogenic conditions: A case study of Oldman River Basin, Canada

Abstract:

Reservoirs are commonly constructed to serve a variety of purposes including flood control and boost of socio-economic activities across various spatiotemporal scales. These infrastructures are often managed using operational rule curves, which are developed considering the long-term understanding of the system’s properties, water availability, and water demand conditions. However, recent changes in natural and anthropogenic conditions have altered the historical characteristics of water availability and demand conditions. This implies that historical rule curves might not necessarily present reliable water allocation plans and there is a need to update these curves considering the changes in water systems in the future. In this study, we focus on the water allocation of the Oldman Reservoir, Canada, which plays a key role in the provision of provincial water demands. We develop a conceptual hydrological model and couple it with a water allocation model to simulate the natural streamflow, reservoir storage, as well as allocated flow to water users in this area. We generate scenarios of change in streamflow and agricultural water demand considering the outputs of climate models. Using the developed coupled model we assess the system vulnerability based on the historical operational rule curves of the Oldman reservoir under noted changing conditions. Accordingly, we produce a large ensemble of rule curves to find the sets that lead to robust water allocation plans. The results show that using the proposed sets of operational rule curves the reliability of water supply system can be increased under changing conditions.