For the record, I don't recall starting any thread in the "Environment" subforum before, but I figure this is the correct place for a discussion of hydropower and dams. Consider these IEA hydropower statistics (created June 25, 2016) for a moment:
Percent of world’s electricity produced by Hydropower: 21 %
Total number of people that hydropower supplies with energy: 1,250,000,000
Percent of U.S. energy supplied by Hydropower: 9.25 %
Percent of renewable consumption provided by Hydropower in the U.S.: 49 %
Total number of dams in the U.S.: 80,000
Total number of dams in the U.S. that are utilized for Hydropower: 2,400
Percent of efficiency hydropower turbines can achieve: 95 %
Total number of countries that utilize hydropower: 30 countries
Percent of electricity hydropower provides for the northwestern United States: 70 %
Percent of Norway’s electricity provided by hydropower: 99 %
Percent of New Zealand’s electricity provided by hydropower: 75 %
Cut and pasted today from this page:
http://www.statisticbrain.com/hydropower-statistics/I have also just watched and will separately post my review of the 2014 documentary "DamNation" in the Book/Media section later today.
Speaking as an Electrical Engineer who worked in computers but who has been obsessively studying energy sources for 3+ years, I would like to state a couple of things before the main discussion begins.
Firstly, the drought that afflicted the Western US in recent years appears to be over. Last June when the above statistics were generated, hydropower was 49% of the total "green" energy in the US. Here in Silly Valley, we have 280% of the average rainfall for the 12 months just passed, multiple mudslides, and localized flooding. Although it would take at least two more such wet years before we could declare that "the drought has ended", we at least are no longer facing a dire water shortage, and many of our hydropower facilities that were idled by lower water levels are again online, and the 49% statistic above is likely to go to 50-60% of the "green" energy this year in spite of the increases in wind and solar and other sources.
Secondly is something the documentary above does not state. Hydropower is much beloved by EE's because it is not an intermittent energy source as are wind and solar. A volume of water impounded behind a dam represents an energy store with a known value, that can be utilized at any time needed. It is also uniquely able (for a "green" power source) to be throttled up and down in a short period of time, simply via the mechanical actions in opening and closing sluices and gate valves upstream of the water turbines. In fact, the hydropower dams are a unique variable energy source that enable the much more variable solar and wind sources, by compensating for the intermittent nature of those two green energy sources in particular. It also is an enabler of nuclear power plants, which by their nature are slow to start, stop, and control.
In fact, one of the very few alternatives to hydropower in regard to controllable energy generation is large gas turbine "peaking power plants", which are not particularly efficient forms of fossil fuel energy generation, but are extremely controllable and can be throttled up and down as quickly as can hydropower. Gas supplies are at the moment more than adequate due to "fracking" and similar techniques, not to mention LPG imports from the Middle East, but "Peak Gas" looms in our future.
So the conundrum with hydropower would be:
- It is "green energy", in the sense that it does not emit carbon or waste heat in operation, since nothing is being burned. During construction of course, a lot of petroleum-fuelled machinery is used to move earth and rock, and to manufacture/mix/pour concrete, and coal is used to make the steel reinforcements for the concrete dam and a lot of both steel and copper are used in the huge generators.
- It is intensely destructive of the environment, for the most part in the construction phase, but also on an ongoing basis to a certain degree, as it suppresses the ebb and flow of rivers and removes the periodic floods that naturally renew riparian areas.
- It is the biggest single source of green power, and because it can be throttled, it also enables the more intermittent green energy sources such as wind and solar. The gas turbine alternative consumes FF and emits carbon dioxide.
- The reservoirs created are enjoyable recreation areas with multiple uses - but (being an avid trout fisherman) not as personally enjoyable to me as the natural fisheries the dams destroyed, and the annoyance of the millions of almost identical "clone" fish produced by the government fish hatcheries.
- The flood control and water supplies created are separate benefits, tempered by the fact that they enable us to grow grain in what were once arid desert areas, and enable human habitation in riparian river zones no longer subject to flooding.