The Athabasca River Basin, home to Canada's growing oil sands mining industry, faces challenging trade-offs between energy production and water security. Water demand from the oil sands mining industry is projected to increase as climate change is projected to alter the seasonal freshwater supply. In this study, a range of water management options are developed to investigate the potential trade-offs between the scale of bitumen production and industry growth, water storage requirements, and environmental protection for the aquatic ecosystems, under projections of mid-century climate change. It is projected that water storage will be required to supplement river withdrawals to maintain continuous bitumen production under the impacts of future climate warming. If high growth in future bitumen production and water demand is the priority, then building sufficient water storage capacity to meet industry demand will be comparable to a week of lost revenue because of interrupted production. If environmental protection is prioritized instead, it will require over nine times the water storage costs to maintain water demand under a high industry growth trajectory. Future water use decisions will need to first, determine the scale of industry and environmental protection, and second, balance the costs of water storage against lost revenue because of water shortages that limit bitumen production. This physically based assessment of future water trade-offs can inform water policy, water management decisions, and climate change adaptation plans, with applicability to other regions facing trade-offs between industrial development and ecosystem water needs.