A model to evaluate spatiotemporal variations of hydrological connectivity on a basin-scale complex river network with intensive human activity.

In recent decades, rivers have been among the most gravely disturbed ecosystems due to intense anthropogenic impacts. Accurate spatial evaluation of river network connectivity is necessary for providing an improved empirical basis for management, conservation, and restoration initiatives. In this study, we focused on the stream continuity-oriented hydrological connectivity of the river network ecosystem. An evaluation model was established using spatiotemporal hydrological data, temporal data on dam development, and a new stream continuity-oriented connectivity index (SCI). The Pearl River basin was selected as the study area to demonstrate the model application using data since 1960. The model showed that the SCI values had significantly and steadily decreasing characteristics in the entire basin from 1960 to 2018, with a total decrease during this period of 26% throughout the river network. The connectivity of the river network declined as the number of dams increased, and dams built on main trunks had a larger impact on the connectivity than those on tributaries. These model results can help government regulators identify the worst connected areas of the river network and take effective measures to reduce the impact of human interferences. Thus, the model can provide practical guidance and support to the conservation, management, and restoration of the river ecosystem.