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以大通水文站为代表站,选取1950~2012年共63年的逐日流量资料,分析了最近60多年来长江中下游地区枯水流量的特征。用P-Ⅲ型曲线、广义极值分布模型(GEV)和广义帕累托分布模型(GPD)分别拟合汛期和非汛期的日流量极小值,通过柯尔莫哥洛夫检验(K-S检验)、概率点据相关系数检验(PPCC检验)及均方误差三种方法,检验分布模型的拟合精度。结果表明,长江中下游汛期低流量事件增多、强度增大,非汛期低流量事件减少、强度减弱。三种模型对大通站汛期和非汛期的枯水流量都有较好的拟合精度,但以P-Ⅲ分布模型模拟更优。用P-Ⅲ分布模型模拟的历史低流量事件显示,汛期最强的枯水流量强度达到68年一遇,非汛期最强的低流量事件强度达到38年一遇。在汛期,长江中下游防汛的同时,也要注意防旱。
Taking Datong Hydrographic Station as the representative station, we select the daily flow data of 63 years from 1950 to 2012, and analyze the characteristics of the low flow in the middle and lower reaches of the Yangtze River in the past 60 years. The daily minimums of flood season and non-flood season were fitted by P-Ⅲ curve, GEV and GPD respectively. The Kolmogorov test (KS test ), Probability points according to the correlation coefficient test (PPCC test) and mean square error three methods to test the distribution model fitting accuracy. The results show that the low-flow events in the middle and lower reaches of the Yangtze River flood season increased, the intensity increased, low-flow events in non-flood season decreased, the intensity weakened. The three models have good fitting accuracy for dry flow in flood season and non-flood season of Datong station, but they are better simulated by P-Ⅲ distribution model. The historical low-flow events simulated by the P-Ⅲ distribution model show that the strongest dry flow intensity in flood season reaches 68 years, and the strongest low-flow event intensity in non-flood season reaches 38 years. Flood season, flood control in the middle and lower reaches of the Yangtze River, we must also pay attention to drought.