黄土高原小流域特性指标与产沙统计模式

CHARACTERISTIC INDEX AND STATISTICAL MODEL OF SEDIMENT YIELD IN SMALL DRAINAGE BASINS OF LOESS PLATEAU IN CHINA

本文从黄土高原实际情况出发,在广泛的野外考察基础上,收集了面积在0.193—329km^2的58个小流域(包括21个变量)的系列数据。通过分析筛选,建立了流域地表综合特性指标: I=(R_h^(0.6)·D_h^(0.2)·R_p^(-0.8)·R_s^(-3.5)及宏观的产沙数学模型: M_(sa)/M_(?)=31.829·I^(0.83)为黄土高原的侵蚀分区及流域的综合开发与冶理提供了背景信息。

On the basis of extensive field investigation, the paper incorporates and analyses over 4000 observation data including 21 variables in 1954- 1982, which come from 58 small watersheds with basin area from 0.193km2 to 329km2 located in three pro-vinces (Figure 1.). A few findings are obtained: 1. An effect of runoff and its rate on sediment yield is much more obvious than that of rainfall and its intensity. Analysis indicates that the relation between mo-ludus of total volume of runoff Mw (m3/km2) and that of sediment yield Ms(m3/ km2) during a single flood may be expressed as and that the relation between modulus of total volume of runoff during all of annual flood series producing sediment and that of annual sediment yield Msa(m3/km2) may also be expressed as Considering runoff rate, i. e. the modulus of peak discharge during a minute Mq (m3/km2) and the annual mean modulus of peak discharge during a minute for each of annual flood series Mq(m3/km2), the relations between modulus of sediment yield Ms, Msa and the composite factors (Mw + Mq), (Mwa + Mq) may respectively be expressed as And they all have better correlation coefficients. 2. Characteristic factors of watersheds surface influencing sediment yield are mainly relief ratio Rh, ruggedness number Dh, basin elongation Re, regulation range (including the amount of vegetative cover) Rp and resistance of ground layer to erosion and permeability Rs. With the observation data from 58 of small catchment basins of loess region in China (Table 4.), two regression equations can therefore be derived, in which 3. In view of the fact that basin elongation Re is directly related to relief ratio of catchment basin Rh, the variable Re may therefore be omitted. And the exponent values in regression equations can suitably be modified. Thus, a composite index of basin surface characteristics is given as follows: In order for both sides of equation to be nondimensional number, and from the data of 58 small catchment basins shown in table 4, an equation may be expressed as follows: It is, in effect, a model of sediment yield, which represents the general relationship among the regime of runoff, basin surface characteristics and sediment yield. It is possible that as quantitative basis classifying erosion regions and as a model predicting sediment yield in small watershed with macroscopic approach, it can be employed. 4. From Figure 4 it may roughly be seen that the composite index I values of surface characteristics for various basins with different erosion intensity can be given as follows: