The California water bill now ready for the president’s signature dramatically shifts 25 years of federal policy and culminates a long and fractious campaign born in the drought-stricken San Joaquin Valley. A rough five years in the making, the $558 million bill approved by the Senate early Saturday morning steers more water to farmers, eases dam construction, and funds desalination and recycling projects. Its rocky road to the White House also proved a costly master class in political persistence and adroit maneuvering.