Water flow is a major determinant of physical habitat in streams and rivers.  This in turn is a major determinant of the type and abundance of aquatic plants and animals.  Water flow regime influences the stability and composition of bottom substrates.  In the Middle Snake River, the water flow regime (water quantity, velocity, and variability) is managed for a variety of beneficial uses. In above normal water supply years when all existing water rights are being met for irrigation, hydropower, recharge, and endangered species, there are sometimes opportunities to shape any additional water for the benefit of the Middle Snake River ecosystem.  A good example of this occurred during the summer of 2019 when the Bureau of Reclamation and Idaho Power Company were able to maintain higher than normal river flows well into August by careful management of their contracted water supplies.  This cooperative management of flow provided the river with higher water velocity, greater water depth, and cooler water temperature during the critical summer months.