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.