马占相思人工林和果园地表径流规律的对比研究

SURFACE FLOW IN AN ACACIA MANGIUM PLANTATION AND AN ORCHARD IN HESHAN,GUANGDONG PROVINCE,CHINA

基于连续 5年的观测 ,对比研究了马占相思人工林和果园两种地表类型上地表径流的各自特点 ;讨论了季节性地表径流的差异与系统水分结构问题 ;探讨了根据实际资料求取发生地表产流的降雨量临界值的方法 ,此方法以综合考虑未发生产流的最大降雨量和已发生产流的最小降雨量为基础 ;并得到了如下的一些结果 :1)本区域不同强度的大气降水频度分布比较均匀 ,但降水量主要由少数几场特大降水带来 ,并且降水量的季节分配极不平均 ,湿季 (4～ 9月 )降水量占全年的 85 .5 %。 2 )地表径流的季节差异更大 ,果园在湿季的地表径流量占全年的93.8% ,马占相思林占 95 .1% ,作者认为在降水量存在较大干湿季差别的地区 ,对于越难于发生地表径流的下垫面 ,这个值会越高。3)马占相思地表径流系数在逐年减小 ,果园的变化较大。4)一次性降雨量对地表径流量的影响在这两种地表类型上都很明显 (r>0 .85 ) ;一次性降雨强度对地表径流的影响只有在中等降雨量 (6～ 16 mm)下才表现明显 (r>0 .87) ,对于较小和较大降水量 ,径流量与降雨强度关系都不大 ;径流系数受一次性降雨强度的影响很明显 (林地 r>0 .92 ,果园 r>0 .77)。 5 )马占相思和果园一次性“最大可能”地表径流产流的雨量临界值 ,分别为5 .1m m和 2 .8mm。

The hydrologic characteristics of an Acacia mangium plantation and an orchard w ere studied in order to address the theoretical problem of the relationship betw ween seasonal variation in surface flow and the “water structure” of an ecosys tem. A method for calculating the critical rainfall of overland flow initiation was developed using integrated consideration of both the maximum rainfall possi ble without surface flow and the minimum rainfall leading to surface flow. The f ollowing are the main results: 1) the precipitation frequency for various rainfa ll intensities was evenly distributed; annual rainfall was mainly the result of just a few storms; wet season (Apr.-Sept.) rainfall amounts to 85.5% of yearly gross; 2) the seasonal difference for overland flow was larger than that of rain fall; in the wet season,surface flow of orchard and forested lands accounted for 93.8% and 95.1% of total precipitation respectively; this result is typical of overland flow where large seasonal variation in rainfall occurs; 3) the surface flow coefficient for forested land decreased yearly,while no tendency was appare nt for variation in surface flow with time in orchard land; 4) the relationship b etween overland flow and precipitation in a single event was strong (r>0.85) . rainfall intensity could affect overland flow(with r>0.87) only in medium rainfall event(6-16 mm); however,the surface flow coefficient was apparently af fected by rainfall intensities(r>0.92 for forested land,r>0.77 for orcha rd land); 5) the “most probable” critical rainfall resulting in overland flow was 5.1 mm and 2.8 mm for forested land and orchard,respectively.