[Originally posted at Revmodo (a new site I am doing some writing for). This is a longer article than a lot of my other articles, so I’m not going to recopy the whole thing here, and I’m even putting this portion of it behind a cut. If you want to read it all, read it at Revmodo.]

Flowing water carries more than 800 times as much energy as a comparable volume of air, which makes water power an appealing method for producing electricity. Even before the advent of electricity, water mills were some of the earliest systems that went beyond human- or animal-power to do work. In the electrical age, hydropower has typically been associated with big dams and correspondingly large infrastructures. Capturing the power of enormous volumes of water behind a dam allows hydropower stations to produce billions of killowatt-hours of electricity annually, comparable to other base load power plants. But like other base load plants, there is also a strong downside to big dams that makes them less than environmentally preferable. However, new hydrodynamic systems are coming along that draw power from moving water and are able to produce energy with far less environmental impact.

While pent up artificial lakes are easy to turn into massive power plants, the environmental devastation that comes from the flooding of millions of acres of land, and the disruption of the ecosystem of the river make large-scale hydropower a second-class form of green power, at best. From a carbon perspective, hydropower is certainly preferable to burning fossil fuels. But the associated damages caused by building large-scale hydropower plants — including turning flowing water into lakes and blocking the migration of fish — is such that new dams for generating electrical power are mostly off the table.There are alternatives to creating an enormous lake in order to constantly feed the turbines.

Small-scale turbines that can sit in flowing bodies of water and generate electricity could now be poised to bring a new face to hydropower. These turbines are greener since they don’t require the blockage of waterways and the destruction and flooding of land in order to be able to produce power. Hydrodynamic power works with the energy in moving water, rather than closing off waterways to build up huge reserves of potential energy stored in the water held behind giant dams. Developmental systems from several companies are now exploring the production of more modest amounts of power, but with far lower cost and with much less environmental destruction than that from the creation of dammed hydropower. Companies such as Hydrovolts Inc., Free Flow Power and Verdant Power have different systems to make use of this power, which they are testing in different parts of the country. There are also researchers who are working on other systems that can potentially take advantage of more energy available in slower moving water.

The federal government in the United States has identified this as an as-yet untapped source of power. The existing water infrastructure of the American West offers a great deal of hydropower potential, with the greatest amount found in the states of Colorado, Oregon and Wyoming. A study by the U.S. Department of the Interior’s Bureau of Reclamation found that 1.5 million megawatt-hours of renewable energy could be generated through hydropower without needing to construct new — and environmentally questionable — large-scale dams. Instead, existing waterways and reservoirs can be used to provide electricity in addition to serving water needs of the region. (For comparison, the Hoover Dam power station produces about 4 million megawatt-hours of electricity annually. Think of this as another one-third of a Hoover Dam spread out through the existing water infrastructure.)

Aqueducts and canals represent an available source of power for additional electrical generation. Particularly in the western U.S., where water management is carried out through an extensive infrastructure of constructed canals and waterways, it may be possible to provide power for tens of thousands of additional homes. Existing dams that were built for water management rather than for power generation may be able to be tapped for power production as well, through the installation of smaller scale equipment that can efficiently and cost-effectively produce power from dams that may have previously been thought too small to be useful for power generation.

To make use of this hydrodynamic power, small, in-line turbines can be installed that generate electricity from the flow of water through aqueducts and canals. The turbine sits directly in the waterway, without a dam, which means that the negative impacts to the environment, as well as the infrastructure costs to install this equipment, are greatly reduced.

Because these waterways already constrict the flow of water moving through them, a greater proportion of the energy from the water flow can be captured with this equipment. In a canal, where most of the water flow must go through the turbine, the efficiency can be as high as 60 percent. Depending on the size of the waterway and the flow rate of the water moving through it, turbines can provide electrical output ranging from 1.5 kW to 30 kW. Because many of these waterways have continuous flows of water moving through them, they are well suited to provide additional, continuous power generation for the grid.

The Bureau of Reclamation has over 47,000 miles of canals, laterals, drains, pipelines and tunnels. To find places with hydropower potential, the government study identified those locations where there was at least a 5-foot drop and where the waterway was in operation for at least four months out of the year and where the power generation potential was at least 50 kW (based upon flow rate of canal and the drop height).