LOS ANGELES (AP) — The FBI’s investigation of a state lawmaker has brought attention to an arm of government that is at once indispensable and nearly invisible — public agencies that pipe water to millions of people and vast swaths of farmland yet operate with scant oversight or public scrutiny.

In a state where water, the economy and politics are intertwined, California has hundreds of local agencies that oversee the pumps and pipes that bring water to fields, homes, schools and industry. Yet the agencies’ board elections are often ignored by voters, and little attention is paid to the six-figure salaries, generous pensions and hundreds of millions of dollars in contracts they hand out.

Dozens of water agencies throughout California even ignore the annual requests by the state controller’s office to provide salary and staffing information so it can be available publicly. Such agencies typically break into the headlines only when something goes wrong.

“They are completely under the radar,” said Robert Stern, former president of the Center for Governmental Studies in Los Angeles. “Who are these people? Yet, they have lots of power.”

FBI agents searched Sen. Ron Calderon’s two Sacramento offices last month. They also have sought to question his brother, former Assemblyman Tom Calderon, while at least one other state senator has been subpoenaed to appear before a federal grand jury in Los Angeles.

Three people who have spoken multiple times with the FBI have told The Associated Press that agents initially were interested in virtually anything involving the brothers but more recently narrowed their questions to issues surrounding the Central Basin Municipal Water District, which serves more than 2 million people in working-class and industrial neighborhoods on the fringe of Los Angeles.

Attorneys for the Calderon brothers have said their clients did nothing wrong. Ron Calderon said he couldn’t comment on the ongoing investigation, and he intends to keep his Senate seat. Tom Calderon told The Sacramento Bee that “enemies of Central Basin” are making false allegations.

Neither the FBI nor the U.S. Attorney’s Office in Los Angeles has commented, citing the secrecy of grand jury proceedings.

The district had been paying Tom Calderon $11,000 per month as a consultant. And agents wanted to know about Ron Calderon’s involvement in legislation favoring the small agency, which employees about 20 people.

The three people spoke on condition of anonymity because of concerns the FBI would be upset by public comments about an ongoing investigation.

District officials confirm the agency has received a subpoena but would not comment on details. The agency will “fully cooperate with the investigation,” board member Leticia Vasquez said.

The potential link to the Central Basin district in the federal investigation is only the most recent example of a local water district becoming the subject of public scrutiny because of potential misdeeds. Previous scandals involving water agencies have uncovered fraud, bribes and lavish expenses and travel.

The number of local water agencies in California is staggering and each has its own bureaucracy. The Association of California Water Agencies represents nearly 440 public agencies accounting for about 90 percent of the state’s water use, with the remainder generally provided by private and investor-owned utilities.

Former federal prosecutor Joseph Akrotirianakis says the little-noticed agencies remain ripe targets for abuse, despite increased public awareness after a widely publicized pay scandal involving public officials in the Los Angeles suburb of Bell.

“These are literally open meetings, but are they?” said Akrotirianakis, who handled corruption cases in Los Angeles. “There’s a lot of abuse that goes on without a lot of scrutiny.”

Mike Machado, a former Democratic state senator from Linden, in the Central Valley, recalled working with other lawmakers a decade ago to change the makeup of two district boards, the Central and West basins in the Los Angeles area, to counter concerns about cronyism and high water fees.

Machado, now executive director of the Delta Protection Commission, said water districts provide plum jobs that often are passed around between family and friends. They also become politically powerful fiefdoms that are resistant to change.

“Most of these have pretty good salaries, medical benefits and retirement (pensions). The seats are basically passed down, not necessarily opened up unless someone wants to be aggressive. If you become aggressive, it pits neighbor against neighbor,” he said.

Investigations over the past decade, including ones by the Los Angeles Times and The Sacramento Bee, found that ratepayers’ money has gone to flying lessons and foreign trips for directors, prime rib and shrimp at swearing-in ceremonies, thousands of dollars for meals, tickets to Los Angeles Dodgers baseball games. As in many other public agencies, employee pensions also have been padded.

In 2005, two members of the West Basin’s board were sentenced to federal prison for taking bribes and kickbacks in the awarding of local government contracts.

More recently, the state attorney general weighed in on conflict-of-interest concerns involving Willard Murray, who served simultaneously on West Basin and another water board. The attorney general forced him to leave one position, but it’s still a family affair: the board’s current vice chairman, John W. Murray Jr., is Willard Murray’s second cousin, said Metropolitan Water District spokesman Bob Muir.

When he was a member of the state Assembly, Willard Murray carried legislation in 1995 that allowed members of a public agency to appoint themselves to the board of a metropolitan water district and to vote for their own appointment to the district board. The bill eventually became law.

He drew media attention in 2008 after one district paid him nearly $90,000 over two years to attend meetings and for travel that included a trip to Mexico City.

In the Legislature, efforts to bring greater scrutiny to local water districts have flopped, at least in part because of insider influence.

“They have a lot of money so they’re able to hire good lobbyists or spread money around,” said Joe Canciamilla, a former Democratic assemblyman from the eastern San Francisco Bay Area city of Pittsburg who now is Contra Costa County’s clerk and recorder.

State Controller John Chiang is pushing two bills to bring greater accountability to local water districts, including one that would stiffen penalties if they fail to provide required information on salaries and other financial records.

State records filed with the controller show that six-figure paychecks are common in many local districts — even among smaller ones.

Seventy-one people worked at the Mesa Consolidated Water District in Orange County in 2011, records show, and about a third of them made more than $100,000 a year. The general manager was paid $254,000.

In the Santa Clara Valley Water District, which had 773 workers in 2011, average wages were nearly $110,000. The chief operating officer reported total wages of more than $330,000.

Little has changed since a state audit released in 2004 sampled the practices of eight of the state’s nearly 450 water districts. Auditors found five of the eight had financial reserves so large that they raised questions about whether money should be returned to ratepayers, while three paid their directors to attend questionable events including retirement, anniversary and holiday celebrations.

Part of the problem is no one bothers to look.

“As long as people can turn on their water or turn on their irrigation tap, they’re happy,” said state Sen. Lois Wolk, D-Davis.