Water conflict between human and ecosystem is a key issue for sustainable water resources management. In the past decades, human-oriented regulation of water resources and construction of hydraulic projects for hydropower generation, agricultural irrigation, and flood control has significantly altered natural flows in many rivers, resulting in increasing variances in water availabilities and flow regimes. Particularly, a number of rivers are subjected to extremely high water-extraction rates and the water can hardly reach the sea. Incessant declination in water availabilities has caused a series of impacts on many valuable aquatic habitats, such as riparian floodplains, wetlands, and estuaries. Due to population growth and economic development, enhanced amount of freshwater are expected to be extracted for supporting human activities, further worsening such situations.

Considering complexities of these major river systems, as well as the interactions between human and ecosystems, no clear results could be obtained regarding what unrecoverable and/or recoverable effects would happen because of such profound alterations. Moreover, the alterations may be multiplied by climate change, further affecting water availabilities and thus intensifying water competition between human and ecosystems. In order to achieve sustainable water resources management, fostering a socio-economically and ecologically healthy consensus over water demands by human and ecosystems is of great importance. Environmental flow that can be used to quantify the amount of water needed by a given ecosystem has become a competitive component with human water demand in watershed management. It is thus desired to manage water conflicts between human and ecosystems in the context of river basins.

Thus, this special issue of HESS aims to gather any contributions on research and applications related to the management of water conflicts between human and ecosystems in different river basins.