贵州赤水河流域水土流失敏感性评价

Assessment of soil and water loss sensitivity in Chishui river basin, Guizhou

赤水河流域在人类活动影响下,属于典型的生态脆弱区和水土侵蚀敏感区,水土流失严重且已影响到水质及周边生态环境安全。研究筛选降水侵蚀力(R)、土壤质地(K)、坡度坡向(LS)和地表覆盖(C)为水土流失敏感性影响因子,同时参考研究区石漠化分布情况,运用GIS技术研究贵州赤水河流域8个市县水土流失敏感性空间分布情况,引入水土流失潜在危险指数(SEPDI)评价水土流失敏感危险性。经过研究得出以下结论:①研究区水土流失敏感性属于中等偏上,其中中度和重度敏感区之和占总面积的63%;②各市县水土流失敏感危险性差异较大,危险性最大的是桐梓县,SEPDI为5.36,最小的是赤水市,SEPDI为3.4;③研究区水土流失潜在敏感性随坡度增加先增加后减少,25°~35°SEPDI达到峰值,35°以上的SEPDI下降,这是由于研究区地貌主要为高原山地,人类在8°~35°活动频繁,35°以上人类活动减少、植被增加,水土流失敏感危险性下降;④耕地与未利用用地水土流失风险性更高,土壤表面的覆盖对水土保持至关重要。

Under the influence of human activities, the Chishui river basin is a typical ecologically fragile area and a soil and water loss sensitive area.The soil and water loss in Chishui river basin is serious and has affected the water quality and the safety of the surrounding environment.We selected the rainfall erosivity, soil texture, slope gradient and aspect, and vegetation coverage as the factors influencing the soil and water loss sensitivity, and used the GIS method to study the distribution of soil and water loss sensitivity in 8 cities along the Chishui river basin.Then, the SEPDI was used to describe the risk of soil and water loss.The results showed that:(1)the sensitivity of soil and water loss in the study area was above the average;the moderately and highly sensitive areas accounted for 63% of the study area;(2)there was big difference in the risk of soil and water loss among the cities;Tongzi had the highest SEPDI(5.36),while Chishui had the lowest SEPDI(3.4);(3)the SEPDI rose first and then fell with the increase of the slope gradient, with the peak appearing between 25° to 35°;it was because human activities mainly concentrated between 8° to 35°,while above 35°,human activities decreased and vegetation increased;(4)the cultivated land and unused land had a higher risk of soil and water loss, which indicated that soil surface coverage was critical to soil and water conservation.