6. Concluding Remarks
The world's fresh water resources are unevenly distributed in time and space. Until recently water resource management focused mainly on reallocating water when and where it was required, a supply-side or fragmented approach. Nowadays, it is apparent that water availability is dwindling due to both population growth and increased per capita water use causing often irrepairable damage to the environment. To face this challenge a new holistic, systemic approach, relying on conjunctive use of surface and ground water resources is needed to overcome the current fragmented management of water. This implies long-term planning and management strategies with respect to both water quantity and quality.
To ensure sustainability, water resource systems need to be planned, designed and managed is such a way as to fully meet the social objectives of both present and future generations, while maintaining their ecological, environmental, and hydrological integrity. This imposes constraints on every stage of development from project planning to final operation and management.
This new holistic approach entails system analysis and modeling, which requires the identification, analysis and evaluation of the interactions between all the components of water resource systems over space and time. These components should be integrated into a network or system involving relationships between humans and their institutions, nature and technology. For such systems to be sustainable, they must interact smoothly with other social subsystems and adapt to changes and uncertainties in supply and demands. Multiple alternatives should be defined and evaluated with respect to overall system performance objectives. Managers and decision-makers have to consider a large