南渡江流域枯水流量概率特征及成因与影响研究

Study on Probability Characteristics, Causes and Influences of Low Water Flow in Nandu River Basin

选用6种概率分布函数对南渡江流域龙塘和三滩水文站最小连续7日平均流量(极值流量)进行分析。结果表明,皮尔逊Ⅲ概率分布函数在南渡江流域拟合效果最优;龙塘站极值流量在1985年发生变异,三滩站在1997年发生变异,变异后的流量总体均比变异前大,流域2003年后极值流量存在下降趋势,枯水发生频率有所增加;1985年后,降水量增多、水利工程和植被覆盖率增加使得龙塘站枯水流量迅速上升,2003年后枯水径流的下降主要与降水相关;三滩站在1997年变异前枯水流量的变化主要和降雨有关,流域内森林覆盖率的增加和降水量的上升是造成三滩枯水流量1997年上升的重要原因。

Six kinds of probability distribution functions are used to analyze the minimum continuous seven-day flow( extreme flow) of Longtang and Santan hydrological stations in Nandu River Basin. The results show that:( a) the Pearson III probability distribution function has best fitting effect in the basin;( b) the extreme flows in Longtang and Santan stations mutate in 1985 and 1997 respectively, the flows after mutation are generally larger than that before the mutation, and after 2003, the extreme flow of the river basin shows a downward trend and the frequency of dry water is increased;( c) the increases of precipitation,water conservancy projects and vegetation coverage after 1985 has led to the rapid increase of dry water flow at Longtang Station, and the decrease of dry water runoff after 2003 is mainly related to precipitation;and( d) the change of dry water flow before the flow mutation of Santan Station in 1997 is mainly related to precipitation, and the main causes for the increase of dry water flow in Santan Station in 1997 are the increases of forest coverage and precipitation in the basin.