太平溪小流域水土保持蓄水减沙效益初步研究

Preliminary analysis on soil water conservation effects for a small river(Taipingxi) basin

太平溪小流域地处三峡库首宜昌县西部，距三峡坝址５ｋｍ的长江西陵峡北岸，治理前水土流失严重，大量坡面产沙以沟道推移方式直接进入三峡库区。１９８３年国家在葛洲坝库区、三峡库区先后开展了大规模的水土流失综合防治工程，成效卓越。经过连续１０年的水土保持综合治理，太平溪小流域水土保持蓄水减沙效益明显，主要表现在：在小流域内建立了水土流失综合防护体系，使河道径流量减少１８．９％～２５．７５％，入库泥沙减少４５．０％～７４．１２％，土壤田间持水量提高２５．７５％～３３．９％，洪峰峰值降低２２．６％，枯水补给河道能力年均提高７．０％；水土保持措施对流域的减沙贡献占８０．４％。

Taipingxi basin is located on the west of Yichang county and north bank of Xiling Gorge,5 km from the damsite of the TGP.Before harnessing,the soil and water loss in this basin was very serious and large amount of sands produced from slope erosion was transported into the Yangtze river directly along trenches.Since 1985,the government has carried out comprehensive soil water loss prevention and harnessing work in the reservoir areas of Gezhouba and Three Gorges successively and obtained good results.The main achievements of soil water conservation in Taipingxi basin include the following:river runoff reduced by 18.9%～25.75% and sand transported into the reservoir reduced by 45%～47.12%,field moisture holding capacity increased by 25.75%～33.9%,the flood peak cut down by 22.6%,and runoff compensation capacity in dry season increased by 7% annually.80.4% of the reduced sand in the basin is attributed to soil water conservation measures.