河岸带耕地降雨径流产流特征分析

在孟津黄河漫滩的河岸带上开展了野外定位观测，研究了自然降雨情况下，河岸林地转变成农耕地前后降雨地表径流产流的污染特征。结果表明，河岸滩区具有较强的土壤人渗能力，径流产流的次降雨量临界值为20mm；滩区径流系数相对偏小：耕地平均3．5％，林地平均2．0％；在耕地开垦初期，由于雨滴的直接溅蚀，表土存在“板结”现象，径流系数增加较为明显。河岸滩区的降雨径流呈弱碱性（pH=8．0—9．5），且盐分含量偏高；耕地径流和林地径流水质的差异表现在耕地径流具有较低的高锰酸盐指数和总氮含量；由于耕地的径流产生量明显大于林地，耕地径流的污染物（土壤颗粒物、有机物、总氮和总磷）产生总量约是林地径流的1．5-3．0倍。土壤翻动后的首次降雨通常会引起耕地较平时5—10倍的土壤颗粒物和总磷流失。林改耕后，径流颗粒物和总磷含量较参照耕地平均增加3倍，成为滨河漫滩农田开垦初期的应首要控制的污染物。河岸滩区在河岸缓冲、屏障和面源污染物削减方面具有重要的水文生态功能，因此在河岸滩区的开发进程中，应注重加强对原生河岸带的生态保护与管理。

Research on the Characteristics of the Rainfall Runoff in Riparian Farmland

On the basic of field experiments in Mengjin floodplain of Yellow River, the characteristics of the pollution in runoff generating under the natural rainfall circumstances were researched in riparian farmland, which had been changed from woodland. The results showed that the riparian floodplain had strong soil infiltration capacity; The critical value of rainfalls that runoff occur observably was 20 ram; The runoff coefficient was small comparatively：an average of 3.5% in farulland and an average of 2.0% in woodland. The soil harden phenomenon occured on the surface soil because of the direct splash erosion of raindrop, so the runoff coefficient increased observably early in the cultivation of farmland.The runoff in riparian floodplain was weak alkaline （pH = 8.0-9.5 ） and high levels of salt. Runoff in farmland had lower levels of hypermanganate index and total nitrogen than that in woodland. Because runoff generating in farmland was more than that in woodland, the gross pollutants （ soil particles, organic matter, nitrogen and phosphorus ） in farmland runoff was about 1.5 -3.0 times more than that in woodland runoff. The first rainfall behind the surface soil being stirred for cultivation would result in 5-10 times of the soil particles and the total phosphorus loss via runoff than the usual. After the riparian woodland had been changed into farmland, the soil particles and the total phosphorus loss via runoff increased largely, which were averagely three times more than before, so the soil particles and the total phosphorus are the chief pollutants, which should be controlled strictly early in the riparian reclamation. Because of the important bio-hydrology functions in riparian such as riparian buffer, harrier and cutting the non-point source pollution, the ecological protection and management of the original riparian should be reinforced.