PORTLAND – Hydropower will most sustainably take us into our energy future.

In the 11th century, the power of rivers was harnessed to grind grains into flour.

By the mid-1800s, fossil fuels were discovered and began to be used prolifically.

By 1920, hydropower generated almost 40 percent of the United States’ electricity.

As fossil fuels became more prevalent, the use of hydropower dwindled. It was after the fossil fuel scare that hydropower came back. Its use has more than doubled since the 1970s, and today, hydropower accounts for about 30 percent of the world’s energy, the most of any renewable energy source.

And now our air is polluted with carbon dioxide, our fossil fuels are running out and we need a source of energy to take us into our future. Hydropower is the best energy source available for our future energy needs — it is commonly used already, has a low cost, and is highly efficient.

Hydropower is the most used renewable energy source. It makes up 10 percent of the U.S. energy consumption, and in some places, such as the Democratic Republic of Congo and the Republic of Georgia, it generates almost 100 percent of the energy consumed.

Hydropower is already very widely used by many countries in different economic standings. The Democratic Republic of Congo is one of the poorest countries in the world, and economically, it makes more sense for the country to use hydropower rather than fossil fuels.

This is true for many other countries around the world. Countries that are poor and are at a disadvantage have the resources to build a hydropower plant, but do not have the resources to drill or import fossil fuels.

Another reason hydropower is so widely used is its versatility. Many water sources can be used to produce power. Dams can be made to fit any gorge or river. They can be on a rushing river or a waterfall.

Engineers have even figured out how to harness the energy of the ocean tides and their large, crashing waves. It is true that hydropower is the most used renewable source of energy, but it also is inexpensive.

The high cost of renewable energy is usually the factor that reduces the public’s desire for clean energy. Hydropower addresses that worry.

Currently, hydropower costs about 2 cents per kilowatt-hour, which is about one-tenth of the cost of solar power. The TidGen turbine in Cobscook Bay, which generates energy from the ocean currents, cost roughly $21 million when created, while one nuclear plant costs about $14 billion.

The TidGen turbine produces 150 kilowatts of electricity, about enough for 25 to 30 homes, but it is constantly being improved and there are hopes for it to produce 5 megawatts, enough to power 2,000 homes.

The Hoover Dam on the Colorado River generates an average of 4.2 terawatts of electricity per year, and supplies electricity for large parts of California, Nevada and Arizona.

At the time it was built, the dam cost about $50 million, which is still significantly less than a nuclear power plant. If consumers are looking for a low-cost renewable energy source that is also efficient, hydropower is there for them.

Unlike fossil fuels, hydropower is highly efficient. Most fossil fuels range from a 30 percent to 40 percent efficiency rate. Hydropower, however, is around 90 percent efficient. Only 10 percent of the energy generated is lost on its way to the grid, so the cost of electricity is less than it would be if you were burning fossil fuels.

It also keeps us from wasting the money it takes to run a hydroelectric plant. This also contributes to the cost advantage of hydropower. Wastefulness is a large problem in our society, whether it be water, food or energy. Hydropower reinforces the movement to begin wasting less.

There is a constant search for an energy source that can viably take us into the future, and hydropower can do just that. With its popularity, low cost and high efficiency, hydropower can be the answer to all our energy needs.

All the resources needed to construct dams and turbines can be easily accessed. All that’s needed now is the investment, which will pay off in a decade or two by supplying energy for thousands of people, if not hundreds of thousands.

Rose Griffin is a resident of Portland.