关键词: 自然地理类型, 流域产沙量, 降雨

Abstract: Nineteen river basins in different geographical environments have been chosen to study the relations of sediment yield and rainfall in the Middle Yellow River Basin. Four major types of river basins were categorized, i.e., loess river basin with low vegetation coverage, mixed loess and rocky basin, rocky basin partly covered by loess and rocky basin. A composite index K was used as rainfall index for analysis of relations of sediment yield and rainfall. It was showed by data plotting that obvious positive relation exists between specific sediment yield and rainfall index K . The slope of line much varied from one type of river basins to another, indicating different rates at which specific sediment yield increases with the increase of rainfall index K . Moreover, obvious variation of specific sediment yield was observed for the same K value. Specific sediment yield tends to become increasingly greater from the south to the north within the studied area as index K increases. The environment features of river basins contribute a great deal to the control of the relations of specific sediment yield and rainfall index. An index VSD, integrated vegetation cover, surface material and morphological features, was used to indicate the resistance of river basin environment to erosion and relate to he specific sediment yield of river basin. It was revealed that specific sediment yield has obviously positive relations to the index VSD . It is of great interest that the places where different river basins were located on the plotting diagram are perfectly coincided with those on the diagram of the relation of specific sediment yield and rainfall K . Since rainfall index K relates to both rainstorms and the total rainfall different frequencies and intensities of rainstorms could occur for the same K value. By comparing the temporal variations of specific rainfalls with specific sediment yield, it was shown that the peaks of specific sediment yield could be produced either by one rainstorm event or by several rainstorm events, even the total volume of precipitation.

Key words: physio-geographical types, sediment yield, rainfa