These mountains run north-south for almost the entire length of Oahu Island
, creating a windward and a leeward side. Mount Kaala at 4,020 feet is the tallest point.
While not technically a river, the Kaukonahua is the state's longest stream. It runs 30 miles through the plateau. Wahiawa Resevoir is Oahu Island's main fresh water source with 302 acres.