Central Valley farmers and their elected leaders converged on Sacramento on Tuesday to accuse the state of engineering a water grab that puts the fate of fish above their fields and jeopardizes a thriving agricultural economy. The allegations came at a meeting of the powerful State Water Resources Control Board, which recently unveiled a far-reaching plan to shore up the health of the Sacramento-San Joaquin River Delta, the West Coast’s largest estuary and a source of water for much of California.