In this remarkable water year, which ended more than five years of severe drought in most areas of California, there are still plenty of noteworthy water questions to contemplate and act upon. Here’s the central one: Three years after California passed what’s often called a landmark groundwater regulation law, no one knows how much under-surface water remains accessible to wells and no one has a clue about how much replenishment the state’s supplies actually got from the winter’s massive storms.