History of Japan Ancient Japan to 1185

Drainage and soils

Drainage

waterfall in Yamanashi prefecture
The increasing demand for freshwater for use in paddy (wet-rice) cultivation and industry and for domestic consumption is a serious problem. Difficulties of supply lie in the paucity of natural water reservoirs, the swift runoff of the rivers, and the engineering difficulties of constructing large-scale dams in the rugged mountains.

Ishikari River
Japan’s rivers are generally short and swift-running and are supplied by small drainage basins. The most significant rivers are the Teshio and Ishikari rivers of Hokkaido; the Kitakami, Tone, Shinano, Kiso, and Tenryū rivers of Honshu; and the Chikugo River of Kyushu. Some of the rivers from the volcanic areas of northeastern Honshu are acidic and are useless for irrigation and other purposes.

Ukimi Temple
Lake Biwa, the largest in Japan, covers 259 square miles (670 square km) of central Honshu. All other major lakes are in the northeast. Most of the coastal lakes, such as Lakes Kasumi and Hamana of Honshu, are drowned former valleys, the bay mouths of which have been dammed by sandbars. Inland lakes such as Biwa, Suwa, and Inawashiro of Honshu occupy tectonic depressions of geologically recent fault origin. Lakes of volcanic origin (e.g., Kutcharo of Hokkaido and Towada and Ashi of Honshu) outnumber all other types.

The environment

The tremendous growth in population from the late 19th to the mid-20th century and the rapid industrialization after 1945 put increased pressure on Japan’s natural plant and animal communities, primarily through loss of habitat and environmental pollution. Once-abundant creatures, such as the eastern white stork (kōnotori) and the Japanese crested ibis (toki), have become extinct. Awareness of pollution grew from the 1960s, and after 1970 a number of strict measures were taken. Although domestic air and water quality improved, air pollution from the East Asian mainland increased the incidence of acid rain in Japan.
Akira WatanabeYasuo MasaiGil Latz