A controversial plan to transform a tract of the Mojave Desert into a giant water-storage facility was killed yesterday by California’s Metropolitan Water District. First presented in 1997 by Keith Brackpool, an advisor and leading financial backer to Gov. Gray Davis (D), the $150 million project would have entailed the construction of a 35-mile pipeline between the MWD’s Colorado River aqueduct and the Mojave site and a storage facility for 1.5 million acre-feet of water. Brackpool’s Santa Monica-based company, Cadiz Inc., which owns the desert site, might have earned up to $1 billion over the 50-year term of the project. The move to cancel the project was approved by a hair’s breadth — 50.25 percent of the board’s weighted votes spelled the end of the project. Environmentalists, who argued that the project would result in permanent damage to the Mojave National Preserve’s fragile ecosystem, are celebrating the cancellation. Still, questions about Southern California’s future water supply remain unanswered.