A plan to build the largest reservoir in California in decades, Sites Reservoir about 70 miles north of Sacramento, is being challenged as ecologically destructive and not worth the cost in a lawsuit filed by environmental groups Wednesday. The $4.5 billion project, which seeks to boost water supplies for drought-plagued cities and farms, was recently put on the fast track by Gov. Gavin Newsom. The suit, though, alleges the reservoir’s environmental impact report was insufficient, failing to address harm to fish and greenhouse gas emissions — problems opponents say make the additional water hard to justify. “It’s not a negligible...