THE EFFECT OF LAND USES AND RAINFALL REGIMES ON RUNOFF AND SOIL EROSION IN THE SEMI-ARID LOESS HILLY AREA, CHINA

Abstract

The main purpose of this article is to analyze runoff and soil loss in relation to land use and rainfall regimes in a loess hilly area of China. Based on 14 years of field measurements and K-means clustering, 131 rainfall events were classified into three rainfall regimes. Rainfall Regime II is an aggregation of rainfall events with such features as high intensity, short duration and high frequency. Regime I is the aggregation of rainfall events of medium intensity, medium duration and less frequent occurrence. Regime III is the aggregation of events of low intensity and long duration and infrequent occurrence. The following results were found. (1) Mean runoff coefficient and erosion modulus among the five land use types are: cropland > pastureland > woodland > grassland > shrubland. (2) The sensitivity of runoff and erosion to the rainfall regimes differ. Rainfall Regime II causes the greatest proportion of runoff and soil loss, followed by Regime I and Regime III. (3) The processes of runoff and soil loss, however, are complicated and uncertain with the interaction of rainfall and land use. This is mainly due to the different stages of vegetation succession. Based on these results, it was suggested that more attention should be paid to Rainfall Regime II since it had the most erosive effect. Shrubland is the first choice to control soil erosion when land use conversion is implemented, whereas pastureland (alfalfa) is not. Large-scale plantation of alfalfa therefore, should be avoided. Grassland and woodland can be used as important supplements to shrubland.