Characteristics of the changing seasonal water regime in Lake Dongting and their response to the change of river-lake water exchange in recent 30 years

Abstract

The adjustment of river-lake water exchange will cause water regime of lake to change and threat the sustainable development of social economy and ecology. In this paper,based on daily observation data of water level and water discharge from 1981 to2012 at Chenglingji Station,Nanzui Station in Lake Dongting,Yichang Station and Luoshan Station in the main reaches of the Yangtze River,the characteristics of the changing water regime in Lake Dongting and their response to the changes of river-lake water exchange were analyzed by means of unit root test,analysis of variance and the comparison of stage-discharge curve. The results suggestted that the water regime in Lake Dongting showed periodic characteristics during 1981 to 2012. The period of 1981-2002 was viewed as relatively stable phase. Mean water level decreased 0. 43 m in 2003-2012. In the flood season,water level of Lake Dongting decreased 0. 60 m. In the retreating season,water level fell 1. 49 m. In the dry season,water level rose 0. 18 m. The change of water level was not significant in the rising season. The dry season may be early in consideration of 2. 03 m drop in October. The changes of hydrological regime were related to changes of river-lake water exchange: In the flood season,flow diversion at the three outlets reduced and the lake level dropped. In the retreating season,reduced flow diversion at the three outlets coupled with stepping up outflow intensified lake water withdrawal. In the dry season from January to March,outflow slowed down and the lake level rose.