Ron Gastelum, the leader of the powerful agency that supplies nearly all of Southern California with water, announced Tuesday he is quitting after 5 1/2 years. Gastelum, 58, said he planned to remain as the massive agency's president and chief executive officer through Dec. 31, or until his replacement can be found.

Water officials in San Diego and Los Angeles counties praised Gastelum on Tuesday, saying he had done a remarkable job of improving the reliability of Southern California's water supply even as drought and political pressures have tested historic water sources such as the Colorado River.

Gastelum, who earned a salary of $297,000 a year, was the 11th chief executive officer in the Metropolitan Water District's 76-year history.

In a letter to board members, Gastelum said he felt five years was "about the right length of time to set the district on good footing for the future … and that I have other professional dreams I intend to pursue."

Metropolitan, one of the largest public agencies in the country, was created by the California Legislature in 1928 to build and operate the Colorado River Aqueduct in order to bring water to population-rich and water-starved Southern California. The agency supplies drinking water to more than 18 million Southern California residents in six counties -- including San Diego County -- by selling it to 23 member cities and agencies.

A lawyer who once served on Metropolitan's board of directors, Gastelum was the first former board member, and first Latino, to be named as the agency's chief executive officer.

Officials from the San Diego County Water Authority -- which has often clashed with Metropolitan over the past decade over water policy issues -- did not return calls Tuesday.

Longtime local water officials praised Gastelum for moving Metropolitan into finding more water through nontraditional supplies, including buying water from Northern California farmers in water "transfers" and storing water underground that could be used in droughts.

In 2003, Metropolitan was forced to cut drastically its reliance upon the Colorado River because of drought and political pressure from other Western states. Despite that, Metropolitan reports it has enough stored water to keep Southern California wet for 20 years.

Gary Arant, general manager of the Valley Center Municipal Water District, said he has known Gastelum since the 1970s, when Arant was a young water district general manager in Los Angeles and Gastelum a young lawyer.

"Ron's been a great leader … we're going to miss him," Arant said.

He said before Gastelum, Metropolitan was "engineering heavy," meaning the agency created new water supplies by building dams and aqueducts, concrete and steel projects that carry heavy environmental impacts.

"(Ron) is an attorney," Arant said. He de-emphasized engineering and kind of said, 'from my perspective we're no longer going to focus on aqueducts. We need to diversify.' "

Other officials said Gastelum made water conservation a policy to create supply rather than just to respond to emergencies such as droughts.

Contact staff writer Gig Conaughton at (760) 739-6696 or gconaughton@nctimes.com.