3.3 Sustainability Criteria
Often conjunctive water use projects involve environmental, economic and social factors that have no numerical scale for assessing their relative importance. Thus scientists and planners have devised various approaches, including weighting, constraints and trade-offs, whereby the above factors may be given assumed values or weights, perhaps based on the findings of opinion polls (Simonovic, 1998). Commonly the issue is comprised under the terms “sustainability” and “sustainable development”. These terms are sometimes used interchangeably, but there is a subtle difference between the two. One useful approach is that sustainable development is the process by which we achieve sustainability. According to the Brundtland Commission’s Report (WCED, 1987), development is sustainable if it meets the needs of the present without jeopardizing the ability of future generations to meet their own needs. The concept is inherently holistic: it implies long-term perspective for planning and integrated policies for implementation and improvement. This improvement over time cannot be achieved without rational management of water resource systems: systems able to meet, now and in the future and to the fullest possible extent, society’s demands for water and the multiple purposes it serves. The demands will include not only the traditional uses of water flows and storage volumes, that depend on the hydrological pattern of the region, but also the preservation and enhancement of the social, cultural and ecological systems. Considering the above definitions and perspectives, sustainable water resources systems are those designed and managed to fully contribute to the objectives of society, now and in the future, while maintaining their ecological, environmental and hydrological integrity (Loucks and Gladwell, 1999).