本文基于淮河流域吴家渡水文监测站1950-2007年月径流量资料,通过定义长、短周期径流旱涝急转指数,分析了淮河流域汛期径流旱涝急转现象(分旱转涝和涝转旱两种类型),研究结果表明:1)长周期径流旱涝急转在1986年以前发生次数较多,而1986年以后发生次数相对较少;2)各相邻月间的短周期旱涝急转的年际振荡以6-7月最多,且其长期变化规律与长周期旱涝急转年际振荡变化相似;3)长、短周期旱涝急转频次呈现不断减少的趋势,但全旱和全涝频次则有增加的趋势;4)2000s汛期长周期旱转涝、短周期6-7月旱转涝有逐渐增加的趋势,分析认为这种旱涝急转变化是导致淮河流域汛期径流量增加的主要原因之一.;Based on the monthly runoff data during 1950-2007 at Wujiadu Hydrologic Station in the Huaihe River Basin, the drought-flood abrupt alternation phenomena(including drought to flood and flood to drought) based on runoff was analyzed during the main rainy season(MJJA) by using long-and short-cycle runoff drought-flood abrupt alternation index(RDFAI). The results are as follows:1) the frequency of long-cycle runoff drought-flood abrupt alternations was higher in the period before 1986, and then decreased after the late 1980s; 2) Inter-annual changes of the short-cycle runoff drought-flood abrupt alternation phenomena between the adjacent months varied from each other, with the change between June and July being the most obvious one, and the long-term changes are similar to that of the long-cycle runoff drought-flood abrupt alternation phenomena; 3) Both the occurrence of long-and short-cycle runoff drought-flood abrupt alternation phenomena showed decreasing trends during the past 57 years, however, the total drought and total flood phenomena were on the rise; 4) During the 2000s, both the long-cycle and short-cycle runoff drought to flood abrupt alternation in June and July increased, and this might be one of the major reasons for the runoff increase during the rainy season at the same period.
The watershed characteristics were analyzed based on DEM and HEC for the major processes of lowland water infilling,calculation of water flow direction,water flow accumulation,and water network layout,finally the digital basin was generated.The Chunhua watershed in Jiangning,southern Jiangsu,was taken as a case study using the new tool set.The results of the study show:the watershed boundary line is almost identical to the ridge line in the mountain areas that are less impacted by human,but the result is much different from the actual watershed in the flat areas or areas that are much impacted by human.The watershed boundary line needs to be revised artificially further.In view of efficiency and precision,it is viable to use this new tool to extract watershed characteristics.
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