Determining water level management strategies for lake protection at the ecosystem level

To prevent lake degradation, water level management has been a major focus of research in the past several decades. There are, however, some shortcomings in the traditional studies, and the protection of entire ecosystems is difficult to achieve in practice. In this paper, the framework of a new method for determining ecosystem-based water level regimes (WLRs) for lake protection is proposed. First, historical WLRs are divided into several sub-stages. Then, ecosystem statuses corresponding to different WLRs are quantified and compared. Finally, parameters of optimal and acceptable WLRs are used to determine water level management goals. The proposed method was applied to Baiyangdian Lake, the largest shallow lake in the North China Plain, to test its effectiveness. Results showed that to protect the ecosystem at the optimal status, 50% of the parameter values should fall within the range of the 25th and 75th percentiles of Stage I; and to protect the ecosystem from reverse succession, 50% of the water level parameter values should fall within the range of the 25th and 75th percentiles of Stage II. This method takes ecosystem status into account, and has high practicability in water resources management.