An integrated connectivity diagnostics and dependency analysis framework for supporting water replenishment management

Abstract

An in-depth investigation on hydrological connectivity and its relationships with water level are fundamental for regional water replenishment management. In this research, an integrated connectivity diagnostics and dependency analysis framework (ICDDAF) was developed for determining the optimal ecological water level in Baiyangdian Wetland, North China. It consisted of two core modules: hydrological connectivity diagnostics (HCD) and hydrological connectivity–water level coexistence analysis (HC–WLCA). The results were as follows. 1) In the HCD module, remote sensing coupling geostatistical connectivity function methods can accurately evaluate the hydrological connectivity considering the directional difference and the validity of distance range. For intra–annual variations, the hydrological connectivity was relatively good in March at the monthly scale, spring at the seasonal scale and the west–east direction, while relatively weak in September and summer, which were related to the periodic characteristics of vegetation growth, overall terrain and flow direction. For inter–annual variations, it was generally weak and showed a downwards, then upwards and finally downwards trend. 2) In the HC–WLCA module, Multivariate Copula Analysis Toolbox was innovatively adopted to describe the coexistence relationships of hydrological connectivity and water level. Beta and generalized Pareto distributions were selected as the optimal marginal distributions for hydrological connectivity and water level indicators respectively, and Frank copula was determined as the optimal joint distribution function; the modelling uncertainty in the coexistence relationships was focused. 3) The water level of 7 m was determined as the optimal ecological water level for maintaining good hydrological connectivity and restoring ecological environment. Considering the coexistence relationships of hydrological connectivity and water level, such an ICDDAF can provide a new perspective for efficient adjustments of water levels based on hydrological connectivity pattern variations under different water replenishment schemes, aiming to achieve ecological restoration of wetlands.