Role of flood storage ability of lakes in the Changjiang River catchment

Almost every year, China is affected by severe flooding, which causes considerable economic loss and serious damage to towns and farms, in particular, at the middle and lower regions of Changjiang (Yangtze) River. In addition to abnormal weather, previous research has concluded that artificial effects have also been significant causes of major flood disasters along this catchment. These have included (i) extreme deforestation and soil erosion in the upper reaches, (ii) shrinking of lake water volumes and their reduced connection with the Changjiang River due to reclamation of lakes that retarded water in the middle reaches, and (iii) restriction of channel capacity following levee construction. The present research focused on the flood storage ability of Dongting and Poyang Lake in the middle region and simulated the water/heat dynamics for the 1998 large-scale flood, which was one of the largest floods in the 20th century, in the entire Changjiang River catchment. The authors expanded the process-based model for application to broader catchments in order to evaluate large-scale flooding in the Changjiang River (NICE-FLD), and compared the severe flood-period of 1998 with the usual flood-period of 1987-1988. The model reproduced excellently the river discharge, soil moisture, evapotranspiration, groundwater level, and other factors. Furthermore, the authors conducted the back-casting simulation by recreating the areas of both lakes in the 1950s and by inputting the meteorological data in the 1998 severe flood in order to evaluate the role of flood storage ability of lakes. The simulation shows that the peak flow and groundwater level around the junction and downstream from it decrease as qualitatively described by the previous researches. This indicates that the increase of lake storage capacity moderates the peak value of lake water level during the flood periods and decreases the groundwater level surrounding the lakes. This result is very important for minimizing flood damage as far as possible and making the better decision on sustainable development in the catchment. (C) 2008 Elsevier B.V. All rights reserved.