1956~2011年鄱阳湖水沙特征及其变化规律分析

近年来,鄱阳湖水沙研究集中在鄱阳湖"五河"各水文站的单站分析上,且水沙数据采用大多仅至21世纪初期,对缺测资料未进行有效插补。将鄱阳湖作为一个研究整体,分析了鄱阳湖水沙特征及其变化规律,以便为鄱阳湖泊形态变化研究以及水、沙资源的合理开发利用提供有利的参考依据。运用水沙相关、上下游泥沙相关法对部分缺测泥沙进行插补,获得1956~2011年的鄱阳湖入、出湖水沙系列数据。利用数理统计法、水沙双累积曲线法、Mann-Kendall法分析鄱阳湖入、出湖径流量与输沙量变化特征,并且探讨了水沙变化的原因。结果表明:(1)入湖径流量和输沙量的年内分配相一致,而长江水沙的倒灌影响了出湖径流量和输沙量的年内分配;(2)鄱阳湖入湖悬移质泥沙从90年代开始下降趋势加剧,而出湖悬移质泥沙1956~2000年整体呈下降趋势,2001~2011年呈现上升趋势;(3)鄱阳湖入、出湖年输沙量出现明显的突变点分别在1998年左右、2003年左右;(4)径流量总体处于相对稳定状态,但近10a来径流量略下降,主要受到降水量变少的影响,入湖输沙量变化受"五河"流域的水库蓄水拦沙、流域水土保持工作加强、人类河床采砂等因素影响;而出湖河段河床深度下切、江湖水面比降加大、人类在鄱阳湖采砂扰动河(湖)床均加大了近10a来出湖悬移质泥沙的输出。

CHARACTERISTICS OF RUNOFF-SEDIMENT INTO AND OUT OF THE POYANG LAKE FROM 1956 TO 2011

In recent years, there are more and more researchers who conducted studies on the Poyang Lake about the water and sediment transport. However, they mainly focused on statistical analysis of water and sediment data at five hydrologic stations on the Ganjiang River, Fuhe River, Xinjiang River, Raohe River, Xiushui River. The data were obtained from 1956 to 2005 and the missing data were not interpolated in those researches.In this study we took the variation characteristics of runoff and sediment transport of the Poyang Lake as a whole. Studies of water and sediment transport characteristics provide evidence for researching the change in the morphology, and could give reasonable guidance in exploitation and utilization of soil and water resources in the Poyang Lake. Firstly, we used two methods to interpolate the lack of measurement data in the Poyang Lake from 1956 to 2011. Secondly, the variation characteristics of runoff and sediment transport at important hydrometric stations of the Poyang Lake were analyzed by using mathematical statistics, the double accumulative curve of annual runoff and sediment and the Mann-Kendall method, based on the data from 1956 to 2011. Then we studied the causes of the variation characteristics of runoff and sediment transport in recent decades. The results showed that: 1) The annual distribution of runoff into the lake was consistent with sediment load, however, the phenomenon of the Yangtze River water and sediment flow backward influenced the annual distribution of runoff and sediment transport out of the lake; 2) The trend of the annual variation of the suspension sediment load into the Poyang lake began to intensively decline from the 1990s, but the suspension sediment load out of the Poyang lake presented a whole descending trend from 1956 to 2000, the data also demonstrated that the suspension sediment load out the Poyang lake is on the increase from 2001 to 2011; 3) Sediment load into the Poyang lake appeared to be a mutation point around 1998, sediment load out of the Poyang lake occurred around 2003. 4) Change of runoff transport tended to be a relatively stable state in the 56 years, but in recent decades, it has close relationship with the influence of the precipitation in the Poyang Lake basin. Then change of sediment transport of Poyang Lake is relatively complicated. Sediment load into the lake was significantly reduced, but sediment load out of the lake increased obviously. The reasons caused reduced sediment load into the lake include: ① There were many reservoirs in five rivers of Poyang Lake, which had function of water storage and sediment retaining, such as Wanan reservoir. ② The government strengthened soil and water conservation in the Poyang lake basin so that this measure can obviously decrease sediment load. ③ The downstream of the five rivers were infected by the sand-excavation on the river channel, which led to reduced sediment load into the lake. However, there were many reasons which induced increasing sediment load out of the lake: ① The depth of river bed was decreased in Hukou. ② Influenced by the Three-Gorges Project, gradient ration about the Poyang Lake and Yangtze River was increased. ③ Sand mining could cause the disturbance of the river bed so that the river flowing velocity became faster.