Nahai's resignation certainly stunned many at the DWP and at City Hall.
After several water main breaks, Nahai was under a lot of criticism but few expected this sudden resignation.
Nahai has been the head of the DWP since December of 2007. In a four-page letter dated Thursday, he touts the department's achievements.
He closes by saying, "I leave with nothing but fond memories of my time at DWP and immense pride at what we have accomplished. However it is time for me to explore other opportunities."
"All I know is that he is moving on to the Clinton initiatives, which will also be great for the whole nation, but he was a terrific general manager here at the city, and so I'm puzzled frankly as to why he's leaving, or what the back story is," says Bill Rosendahl of the L.A. City Council.
The mayor, who is out of town, issued a short statement saying in part, "I would like to thank David Nahai for his four years of service at the Los Angeles Department of Water and Power? I wish him great success in his new endeavor as Senior Advisor to the Clinton Climate Initiative."
Nahai has been under a lot of criticism lately after a huge water main break on Coldwater Canyon in Studio City, a sinkhole in Valley Village that caused a fire truck to sink and a number of other leaks that leads some to wonder if there something wrong with the system.
"I was certainly critical of the department in general when we've been seeing these pipes burst," says Eric Garcetti of the L.A. City Council.
"I was actually pleased with the answers we got in counsel, and it made me feel like he understood the problem as much as anyone does and was moving to correct it. So it's too bad that we will have a leadership change in the midst of that," Garcetti adds.
"Not that he's personally responsible for it, but sometimes the person that's the general manager ends up taking the heat and when these pipes kept on breaking, not that he can control it, these are situations that take place," says Dennis Zine, another council member.
And now, Deputy Mayor David Freeman, who was the head of the DWP from 1997 until 2001, he's going to be running the department on a temporary basis until someone else can be found.