In a major victory for Sierra river advocates, the East Bay's largest water district said Monday it will drop its plan to enlarge a reservoir in the Sierra foothills, which would have inundated stretch of the Mokelumne River prized by kayakers.

The East Bay Municipal Utility District had argued it needed to either raise its dam to enlarge the reservoir or invest heavily in desalination to meet its needs over the next 30 years.

Conservationists and others sued, saying the district had not considered other alternatives, including investing in the far less controversial Los Vaqueros Reservoir near Brentwood.

The possibility of investing in an expansion of the Contra Costa Water District's reservoir was among the factors that led EBMUD to conclude it did not need to raise the dam at Pardee Reservoir.

The district said its other options for meeting its long term water supply needs included water purchases, groundwater storage and desalination.