Wetland system network analysis for environmental flow allocations in the Baiyangdian Basin, China

Many individual wetlands are hydraulically interconnected and present a specific network structure, which act as a large wetland system. Understanding the environmental flow allocations for a wetland system, instead of an individual wetland, is important for systems-level water resources management and ecological protection. In the present study, ecological network analysis was introduced as a powerful method for developing insights into the integral functional condition of the Baiyangdian wetland system in northern China. We investigated how 6 network functional indicators react to different environmental flow allocations in 16 sequential seasons of four-stage during the period of 1959–1978. Biological productivity in the Baiyangdian Lake was used to verify the validity of these functional indicators. A deviation index (D), which incorporates input ascendency (A0), output ascendency (Ae) and internal ascendency (Ai), was adopted to evaluate the reasonability of environmental flow allocations for the wetland system. Results show that the functional indicators of the wetland system declined continuously during the study period. The average deviation index increased from 0.69 to 1.089, indicating the environmental flow allocations for the wetland system were increasingly inadequate and unreasonable in the study period. On the basis of the above results, an adjustment coefficient was developed to direct the environmental flow allocations for the wetland system within the basin. The present study provides an example of how management actions arising out of network analysis might lead to a better understanding of a wetland system functioning and holistic environmental flow assessment.