黄土高原不同植被覆盖对流域水文的影响

以山西省吉县蔡家川流域为对象,研究了植被覆盖类型对流域水文的影响.结果表明:不同植被覆盖的流域年径流系数分别为:林地流域1.6%～2.3%,以农、牧为主的流域3.1%～3.9%;各流域基流系数差异显著,人工林流域为零,次生林为主的流域1.0%～1.5%,以农、牧为主的流域2.5%～2.8%;在雨季人工林流域的径流总量是次生林流域的3.37倍、农地流域的1.9倍,而农地流域的基流量是次生林流域的2.2倍;短历时高强度降雨条件下,人工林流域、次生林流域地表径流量分别是农地流域的10.8倍和2.2倍;在历时较长的暴雨条件下,人工林流域单位面积上的洪峰流量是农地流域的3.4倍,次生林流域的6.9倍;在长历时、大雨量条件下,农地流域的径流量是次生林流域的1.8倍.水平梯田的水源涵养功能与次生林植被相当,次生林植被的水源涵养功能远好于人工植被,在水资源短缺的黄土高原应提倡植被的自然恢复.

Hydrological response to changes in vegetation covers of small watersheds on the Loess Plateau

The study was conducted in the Caijiachuan watershed in Ji County, Shanxi Province. The primary objective was to quantify streamflow differences among small watersheds with different vegetation covers. Annual runoff coefficient ranged 1.6%-2.3% and 3.1%-3.9 % in the forested and the non-forested watersheds, respectively. Baseflow was negligible in artificial forest watershed, and but baseflow ratio (baseflow/total flow) was higher (1.0%-1.5%) in other forest watersheds. In the non-forested watersheds, base runoff coefficient was highest (2.5%-2.8%). During the rainy season in June-September, total runoff from the artificial forest watershed was highest, about 3.4 times of the natural forest watershed, or 1.9 times of the agricultural watershed. The baseflow in the agricultural watershed was highest, about 2.2 times of the natural forest watershed. For storm events with short duration and high intensity, runoff from the artificial forest watershed was highest, about 10.8 times of agricultural watershed. For storm events with a long duration, peak discharge per unit area in the artificial forest watershed was highest, about as 6.9 times of the natural forest watershed. For large storm events with a long duration, runoff in the agricultural watershed was highest, about 1.8 times of the natural forest watershed. Compare with all landuses and vegetation covers, bench terraces and natural forests could greatly reduce overland flow and had large water storing capacity. We found the artificial forests did not have the hydrologic functions to reduce peakflows. We conclude that natural vegetation recovery had the best hydrologic benefits in soil conservation and thus should be promoted in the Loess Plateau area.