A proposal to make California’s drought-era water restrictions permanent could allow the state to chip away at long-held water rights in an unprecedented power grab, representatives from water districts and other users told regulators Tuesday. Members of the state Water Resources Control Board delayed a decision about whether to bring back what had been temporary water bans from California’s drought, spanning 2013 to 2017. The plan is part of an effort to make water conservation a way of life, with climate change expected to lead to longer, more severe droughts.