Analysis of the water level drop in the tail zone of the largest tributary of Poyang Lake, China

Abstract

In recent years, the tail zone of the largest tributary of the largest freshwater lake, Poyang Lake in China, has been challenged by serious water scarcity caused by the drop of the water level during dry season. It is difficult to establish effective remedial measures because of the lack of research regarding the causes of the water level drop. Therefore, this phenomenon and its causes were analyzed in this study. First, a series of daily discharge and water level data from six hydrological and water level stations that has been recorded since the 1950s was used to determine the historical trends in the dry water level using the Mann–Kendall test. Based on the combination of topographic data of typical cross section and classic water conservancy equations, the causes of the water level decrease were studied. The results show that the water level drop in this region was not notable until 2003. Subsequently, continuous deterioration became noticeable. Influenced by various factors, the cumulative water level drop in the dry season reached 4.06 m. This demonstrates the weak correlation between the water level drop and inflow. Instead, the water level decrease was mainly affected by the riverbed undercutting and slightly influenced by changes of the water level in the four lower branches. Effective alleviation strategies should include the strict limitation of the incision of the riverbed and increase in the downstream water level.