d. Irrigation, drainage t and erosion 



(1) Irrigation is practiced on most of the soil areas used 

 for the production of rice and many of the areas where 

 vegetables are grown. Irrigation makes possible the 

 utilization of drouthy soil areas. Even steep hillsides 

 are used for the production of paddy rice. Stream di- 

 versions furnish about 65 percent of the water for irri- 

 gation. Reservoirs, lakes, and ponds supply most of the 

 remainder, bat wells are also used. 



(2) Drainage has been important in reclaiming agricultural 

 soil areas from shallow lakes, bays, and swampy areas. 

 It has also increased the productivity of some poorly 

 drained areas, formerly adapted only to the growth of 

 rice, by increasing the yield of rice and making possible 

 the growth of a winter crop such as wheat or barley. 



In naturally better drained sites, where the climate is 

 suitable, it is the practice to drain the rice paddies 

 in the fall eind grow winter crops on these areas. 



(3) Water erosion is active on many of the non-arable, hillyj 

 and mountainous areas of southern Honshu, Shikoku, and 

 Kyushu. Some areas are nearly barren and badly gullied, 

 while many others have lost considerable surface soil by 

 less obvious sheet and rill erosion. Wind erosion is 

 reTiorted to be active in some dark colored, volcanic 

 ash-derived soil areas during certain seasons unless 

 adequate precautions are taken following cultivation. 



9. POLITICAL DIVISIONS (See Plate 8) . 



a. Administrative regions (chiho) 



(1) Established in July 1943 



(2) llames of regions 



(a 

 (b 

 (c 



(d 

 (e 



(f 



is 



(h 

 (i 



Hokkai (all of Hokkaido) 

 Tohoku (northern Honshu) 

 Hokuriku (west central Honshu) 

 Kanto (Tokyo plain region) 

 Tokai (central Honshu) 

 Kinki (Kyoto, Osaka, etc) 

 Chugoku (western Honshu) 

 Shikoku^ 

 Kyushu 



(3) Map of these regions in ASi' Manual M 354-2B and JAKIS 

 85, Chapter X 



18 



