“We have been getting no love from them, from that place at all,” Mr. Baraka said , adding that he was not criticizing the federal scientists on the ground in Newark.

Mr. Baraka defended his decision to appoint Kareem Adeem as acting director of the water department in November, overseeing a system that provides water to 400,000 people in the city and surrounding communities .

In 2011, Mr. Adeem was released from federal prison after serving four years for conspiring to sell five kilograms of cocaine, according to court records.

Mr. Adeem, who worked lower-level jobs in the department before prison , received the $130,000-a-year position but does not have a college degree. He was deputy director of the department before becoming acting director.

“His knowledge of this stuff is unparalleled,” Mr. Baraka said. “There’s no one else in the city who has the level of information, and I have full confidence that he knows what he’s doing.“

For his part, Mr. Adeem said he and his team were working hard to address the crisis.

“Early on in my life, I made some bad choices,” he said. “I got a second chance. And I’m going to take full advantage of my second chance, helping my city that I love.”

Judith Enck, a former E.P.A. regional administrator whose territory included New Jersey, said officials who run municipal water systems are typically engineers.