Water Department Chief Steps Down in Los Angeles

H. David Nahai, who had been general manager and chief executive of the Water and Power Department since 2007 and a commissioner for two years before that, said in a letter announcing his move that his new job would allow him to focus on “the central challenge of our time, global warming.”

The Clinton Climate Initiative, where he will be a senior adviser, is an effort by former President Bill Clinton’s foundation to study and find solutions to climate change.

Los Angeles residents and the water department’s engineers have been baffled in the past month by a series of major water pipe failures across the city, buckling and flooding streets on several occasions and in one instance partly swallowing a fire truck. The department is investigating the cause.

Officials said privately that Mr. Nahai’s stepping down had nothing to do with the breaks.