PREDICTION OF SEDIMENT REDUCING BENEFIT UNDER DIFFERENT RAINFALL CONDITIONS AND CONTROL DEGREES ON THE LOESS PLATEAU

摘要

Based on the distribution of hydrological stations and zoning of types of soil erosion, the Loess Plateau (3 10 x 10~3km~2) is divided into 292 erosion units. And taking the erosion modulus > 5000t/km~2 as a criterion, the emphasis control area (149 x 10~3km~2) of the Loess Plateau is demarked, and is divided into 10 control regions. The controllable area and the location of control measures are conformed. Level terraces are mainly collocated on the 3° ―15° slopes, woodland and grassland are collocated on the > 15° slopes, and the proportion of woodland to grassland is 8: 2 in the forest belt, 5: 5 in the forest steppe belt, and 2: 8 in the steppe belt. The 9000 combinations of soil-water conservation measures in different rainfall conditions are obtained by the permutation and combination method, according to the 9 rainfall frequencies and the controllable areas of level terrace, woodland and grassland at 10% of control progress rate. The quality standards of level terrace, woodland and grassland are ascertained. The evaluation indexes of soil-water conservation benefits of level terrace, woodland and grassland are established respectively in the condition that rainfall index is higher than that of erosive index of sloping field. Based on the results above, the sediment reducing benefit and soil erosion modulus in the different rainfall conditions and control degrees are analyzed, which could provide a decision-making basis for soil-water loss control on the Loess Plateau.