Hydropower is frequently mentioned in conversations about renewable energy generation in the 21st century. Frequently on World Ocean Radio I have reported on various ocean technologies involving exploitation of water movement such as waves and tides to harness natural capacity not reliant on fossil fuels. Historically dams have also served such a function, from small stream diversion for irrigation to massive structures that have re-engineered a regional landscape to generate serious power capacity distributed nationwide. The United States Army Corps of Engineers lists over 79,000 dams in its national inventory. Some 2,540 dams are regulated as certified energy providers by the Federal Energy Regulatory Commission.

Over the past decade, however, environmentalists have targeted dams as outmoded, inefficient energy providers with serious impacts on water flow, surrounding and downstream environment, species migration and spawning, sediment collection, algae blooms, and other damage to the natural process. Dams have taken on the identity of plaque in arteries, unhealthy intrusions into the water circulatory system that can take on crisis proportion, even deadly consequences. American Rivers and other conservation organizations have taken up the strategy to remove these outdated impediments; some 925 dams have been removed from the inventory over the past 100 years, with recent successes increasing public pressure for more.

Those successes have had some very positive and immediate results. In some instances, the return of ocean fish to freshwater spawning ground, inhibited by the dam, has been observed in less than a month. Fish like alewives, historically essential to the ocean food chain and heretofore threatened, have shown almost instant response to the restoration of the natural passage where once a dam intervened, a natural renewal so essential to their health and proliferation.

But what about the dams remaining? American Rivers suggests six strategies to improve dam operations and to mitigate the economic and environmental impacts, to reconcile the needs of energy suppliers, rate-payers, natural species, and community interests: 1) increase efficiency by retrofitting and improving dams, many of which were constructed 50, even 100 years ago; 2) consider adding capacity to certain existing dams; 3) uphold environmental safeguards; 4) hold hydropower developers responsible for dam safety; 5) design new dams for defined lifetimes; and 6) evaluate dams for production outcome, not size. The Low Impact Hydropower Institute is a new organization dedicated to reducing impact of retrofits and new construction through market incentives and a certification process that evaluates river flows, water quality, fish passage and protection, watershed protection, threatened and endangered species protection, cultural resource protection, recreation, and facilities recommended for removal--standards for public validation of best hydro-practice.

The primary strategy seems mostly about dam removal or modification to acceptable performance of existing installations. New dam construction does not seem to have much of a constituency, projects being inhibited by permitting and regulatory applications and community activists. And frankly, dam removal has its own environmental downsides including removal of flat water reservoir, local wetlands drainage, resultant habitat modification, sediment release, increased stream turbidity, distribution of accumulated toxins downstream, temperature and water quality issues--negatives hopefully to be overcome by restoration of the long-term natural process.
Looking forward is exciting. There are some very interesting new technologies in development for hydro-power: enhanced turbines, for example, generating more energy from the same volume, and small generators built with stock parts and installed in descending sequence in unexpected places like irrigation canals, locks, outlet pipes, storm drains, and existing dams or sites with smaller falls, less than 30 feet from one pool to the next - all resulting in much reduced manufacturing cost, installation cost, operating cost, and environmental impact. The scale of this micro-hydro approach is well suited to developing nations and new installations. Another imaginative example is pumped storage, a system that cycles and recycles a fixed volume of water to gravity fall through a series of miniature blade assemblies to generate enough energy to drive a pumped return cycle and generate surplus electricity for cumulative contribution to the grid and can be built anywhere where there is an appropriate water source. One might even go so far as to imagine such a closed system for a positive re-use of fracked or black water left over from other environmentally degrading systems.

Now wouldn't that be something!