Are the ecological benefits of hydrological connectivity projects continuously increasing? Insights from the perspective of landscape patterns - ecosystem processes - ecosystem services

The construction of hydrological connectivity projects alters the natural morphology and hydrological rhythms of the basin, which can subsequently impact ecological processes and ecosystem services. Quantifying the impacts of hydrological connectivity projects on ecosystems is fundamental for providing theoretical support to researchers and policy makers. Ecological water conveyance projects (EWCP) aimed at ecological restoration are one type of hydrological connectivity projects. In this study, a multi-dimensional hydrological connectivity assessment framework is established to quantify the impacts of the EWCP on landscape patterns. Analytic Hierarchy Process - Entropy Method (AHP-EM) is used to calculate the integrated hydrological connectivity index (IHCI). Ecosystem processes are characterized by vegetation indexes and ecological indexes. The ecosystem services are quantified by ecosystem service value (ESV). An improved ESV calculation method is proposed to assess the ecological benefits of EWCP. This method not only captures the spatial heterogeneity information of land use, vegetation and ecological conditions but also integrates socioeconomic factors. The relationships between trade-offs and synergies among provisioning, regulating, supporting and cultural ecosystem services are clarified to optimize the overall benefits. The results show that hydrological connectivity increases consistently with ecological water conveyance volume (EWCV). ESV is increased positively with IHCI and it shows a correlation with the distance to the riverbank. A new finding is that the ecological benefit shows an inflection point in 2010, which conforms to the "marginal benefit decreasing law". These results provide a new insight on hydrological connectivity dynamics under the influence of EWCP, and the finding has guiding significance for efficient utilization of water resources in EWCP. The methodologies used in this research can be widely applied to other EWCPs.