As countries develop, the demand for water increases while water supply becomes less certain. In general, pressures from both the environment and human activities can increase the likelihood of water scarcity. Climate change is likely to exacerbate the existing demand and supply stresses, particularly when more frequent and extreme droughts and floods, as well as rising sea level are becoming more evident. These various pressures will test the effectiveness of water resource management systems in providing a consistent and secure water supply for all users, with minimum externalities. This study assesses advances in management practices, and institutional and technological innovations for managing water scarcity sustainably under a changing climate. It is a sub-study of the 'Towards green water defence in east Asia' study and it is complemented by another sub-study titled 'Green water defense for flood risk management in East Asia' which focuses on flood management in delta regions.