With resent efforts to promote the tear-down of Hetch Hetchy dam and restore the flooded valley, one must ask why, and not only in the sense of resurrection of the lost valley.
With the approach of global warming, we can expect a continued decrease in snow pack levels. Future precipitation levels are as of yet unknown. If decreased, we need all available storage to last through dry seasons. If increased, we need storage to prevent catastrophic flooding. Above all, with global warming, the snow pack will be replaced by rain, effectively removing our snow pack water storage, and increasing our need for alternative storage.
From the electricity grid point of view, Hetch Hetchy, when water is available, provides a robust predictable and dispatchable power source with no greenhouse gas emission. In addition, the system can also be used to store electricity/energy on a short-term basis through “pump-up” technology. Pump-up is equivalent to having access to a gigantic battery, and is a key component in stabilizing the electric grid. This is especially needed as we introduce alternative and unpredictable power sources such as wind and to some extend solar power.
There’s no question that California hydro power dams have caused severe environmental harm. Almost 3000 miles worth of upset creek/river habitat. But if you compare that to the added safety of flood control, predictable water supply, and reliable and clean energy supply, the end result should favor our dams. We have seen experimentation with fish ladders, and forced water release to preserve smelt populations. Surely there must be more mitigating ideas we can study and introduce.
The bottom line must be this; we need dams and water storage systems. They are a cornerstone of our future survival. Removing dams to restore ecosystems amounts to nothing but a utopian notion.