For the purpose of more detailed description and analysis we have divided China into ten main regions, together with two quite small areas, Hong Kong and Macau. The two latter are not politically part of China and are therefore treated separately from the Si Kiang Basin, of which they form a part. The basis of the regional division is broadly physiographical, i.e. great river basins, plateau and inland drainage basins. Each region (except Hong Kong and Macau) is large; some are immense and are capable of almost infinite sub-division. 1