黄土丘陵沟壑区森林土壤水文行为及其对河川径流的影响

Hydrologic behavior and effect of forest on regulation of river runoff in loess hilly and gully region

通过比较瓦窖沟小流域林地、农田、撂荒地3种主要土地利用方式下的降雨入渗、产流特性及林区与非林区流域径流的季节变化,系统地分析了黄土高原林地水文行为及森林对河川径流的调节作用,主要表现为林地土壤高入渗率、低产流率和强烈的蒸腾耗水作用形成的土壤干层以及森林对河川径流季节分配的均化作用。土壤干层的出现使土壤水库对干旱调节功能丧失,影响林木的持续生长;还将削弱入渗降雨转化为地下水的比例,减少地下水资源的数量,使森林对流域枯季径流的补偿效应受到制约。森林均化径流分配的作用通过削减汛期径流和补充非汛期流水来实现。林区河川径流年内季节分配较非林区均匀,汛期削洪效能明显,并有效地补充了9～11月和3～5月的非汛期流水,补枯效果达4～10个百分点。

The hydrologic behavior of forest soil and effects of forest on the regulation of river runoff were analyzed systematically by comparing of three land use patterns (e. g. forestland, farmland and rang-land) and river runoff in forest area and non-forest area. The results showed that there was a high infiltration rate, low runoff and dry soil profile caused by strong transpiration in forestland. Seasonal distribution of river runoff in forest area become more even than that in non-forest area. The dry soil profile in forest-land, made the regulation capacity of soil reservoir on drought lost, would weaken the proportions of groundwater exchanged from rainfall, and influence the quantity of region water resource and the sustainable development of forest. On the other hand, it would restrict the compensating runoff in dry season. The function of forest averaging seasonal distribution of runoff was realized by reducing the runoff in flood season and compensationg runoff in non-flood season. The benefits of flood reduction by forest were very significant in flood season, and the forest had a better compensatory effect for runoff in dry season, especially from September to November and from March to May, the benefits of compensation reached 4%-10%.