Some dams, such as Lake Oroville in California, do use an afterbay to allow for off-peak water pumping back into the lake (https://norcalwater.org/efficient-wat

Some dams, such as Lake Oroville in California, do use an afterbay to allow for off-peak water pumping back into the lake (https://norcalwater.org/efficient-water-management/efficient-water-management-regional-sustainability/water-maps/oroville/ https://norcalwater.org/efficient-water-management/efficient...). Sadly, dams tend to destroy healthy fishery ecosystems —- a side effect of not “wasting” the water.