Q. I understand hydropower units are LCRA's least costly way to generate electricity. So how come LCRA doesn't run its hydropower units all the time?

A. A relatively inexpensive and clean source of energy, power from LCRA's six hydroelectric dams are its lowest cost way to generate electricity and LCRA's largest source of renewable energy. But because LCRA also is a supplier of another precious commodity — water — to communities throughout Central Texas, generating electricity from the hydrogeneration units takes a backseat to providing water, said Wes Birdwell, LCRA's manager of river operations.

"Hydro is LCRA's cheapest way to generate electricity," Birdwell said. "We don't do that all of the time because we are water limited. If we generated all of the time, we'd drain our water supply, and our hydro has been subordinated to our water demands for the sake of water."

This wasn't always the case. In fact, hydropower once was LCRA's sole source of electrical power. But increased demands for water as well as electricity have long required LCRA to rely on higher capacity power plants fueled by coal and natural gas to serve most customers.

Even so, LCRA continues to use its hydropower units to generate electricity. In fiscal 2001, 3 percent of LCRA's power generation came from hydroelectric dams.

Today, there are three reasons LCRA uses its hydropower units, Birdwell explained. These are:

• As a byproduct when releasing water for water customers.
• During floods when LCRA has surplus water to release.
• And, in emergency power situations.