Assessment of the sustainability of a water resources system expansion

A sustainability assessment method involving risk criteria related to reliability, resilience and vulnerability, has been applied to quantify the relative sustainability of possible expansions of a water resources system in the KwaZulu-Natal province South Africa. A river basin model has been setup for the water resources system, comprising all important water users within the catchment. Measures to meet the growing water demand in the catchment are discussed. Six scenarios including both supply and demand oriented solutions are identified, modelled and compared in tenus of the sustainability criteria. Based on initial experience the method was modified leading to more credible results. A problem with assessing sustainability using risk criteria is a favouring of supply-oriented solutions, in particular when aspects not directly related to demand and availability of water are excluded.