基于SCS法模拟的上海郊区农田地表产流特征及原因

利用上海市近8 a的日降雨数据，采用修正的SCS模型模拟得出上海地区农田地表径流流量，分析出了上海地区农田地表产流的特征。主要结论：（1）旱地在土壤湿度为干燥、几乎饱和、饱和条件下产生地表径流临界降雨量分别为847、358、141 mm；水田的土壤湿度几乎一直为饱和状态，产生地表径流的降雨临界值为026 mm。（2）旱地和水田产流量分布形状都呈极度右偏状，旱地和水田产流最大值分别为13559和18570 mm，但是9811%的天数中旱地产流量小于10 mm，9540%的天数中水田产流量小于20 mm。年产流量在月份中分布比例大体上是以6月和8月为峰的双峰分布，这个峰有从8月向6月前移的趋势。旱地产流量相对于水田的更加集中在5～9月。（3）旱地年产流总天数在50 d左右波动，水田年产流天数在120 d上下波动。旱地连续产流的天数一般不会超过5 d，水田连续产流天数一般不会超过7 d

CHARACTERISTICS OF FARMLAND SURFACE RUNOFF IN THE SUBURB OF SHANGHAI BASED ON SCS METHOD

By using last 8 years daily rainfall data of Shanghai and an improved SCS model,the daily surface runoff of farmland was simulated,then the characteristics of runoff was analyzed.The main conclusions are as follows.The non-irrigated farmland in the antecedent moisture conditions of dry,almost saturated,saturated to produce surface runoff need rainfall 8.47,3.58,1.41 mm respectively.The soil moisture of paddy field are saturated,and the critical rainfall to resulting in runoff is 0.26 mm.The runoff distributions of non-irrigated farmland and paddy field are extremely right skewed.The maximum runoffs in non-irrigated farmland and paddy field are 135.59 and 185.7 mm respectively.But the 98.11% days of flow in non-irrigated farmland are less than 10 mm,the 95.40% days of flow in paddy field are less than 20 mm.Annual flow is a bimodal distribution with the peaks in June and August,and there is a trend that the peak moves from August to June.Compared with the paddy field,the flow of non-irrigated farmland are more concentrated in May~September.There are about 50 days producing flow in non-irrigated farmland every year and the number is about 120 in paddy field.In general,the number of days producing flow continuously is not more than 5 in non-irrigated farmland,and not more than 7 days in paddy field.