Water plays a lead role in the state’s political theater, with Democrats and Republicans polarized, farmers often fighting environmentalists and cities pitted against rural communities. Rivers are overallocated through sloppy water accounting. Groundwater has dwindled as farmers overdraw aquifers. Many communities lack safe drinking water. Native Americans want almost-extinct salmon runs revived. There is talk, too, of new water projects, including a massive new tunnel costing billions of dollars.