Introduction

Some of the most important global concerns at present are climate variability and change, as well as their implications for water resources management. Extreme climatic events have become development challenges of increasing significance from the economic, social and environmental viewpoints, for countries in the global North and South. Uncertainties related to climate change and variability and the associated complexities have made non-climatic factors more relevant, primarily those related to policy-making and implementation, governance, management, development and technological innovation, to mention only some of them. Water scarcity and pollution have been very serious concerns, not only in drought- or flood-prone areas but also in those where rainfall is relatively abundant but subject to poor management, creating potential conflicts between uses and users upstream and downstream. Since planning for greater resilience is becoming a more common feature of metropolitan and regional plans in some developed countries, water security measures have also acquired more importance.