日本一大きい湖は何？
Rivers are generally steep and swift, and few are suitable for navigation except in their lower reaches. Although most rivers are less than 300 kilometers in length, their rapid flow from the mountains provides a valuable, renewable resource: hydroelectric power generation. Japan's hydroelectric power potential has been exploited almost to capacity. Seasonal variations in flow have led to extensive development of flood control measures. Most of the rivers are relatively short. The longest, the Shinano River, which winds through Nagano Prefecture to Niigata Prefecture and flows into the Sea of Japan, is long. The largest freshwater lake is Lake Biwa , northeast of Kyoto.
Lake Biwa