Southern Californians could lose billions of gallons of water a year to Central Valley farmers under a deal Gov. Jerry Brown’s administration has struck with water officials working for President Donald Trump. There’s no guarantee the agreement with Trump will accomplish what Brown’s team is seeking: a lasting compromise on environmental regulations that could stave off significant water shortfalls for farms and cities across California. A powerful state agency, the State Water Resources Control Board, hasn’t yet signed off on Brown’s compromise environmental proposal. Environmental groups have called the governor’s idea woefully insufficient to save ailing fish populations.