Uncertain Water Balance-Based Sustainability Index of Supply and Demand

In order to plan for future water resource development, estimating sustainable levels of water supply and demand is essential to ensure that available water can be used in a way that satisfies all sectors. Different indices have been used to assess the sustainability of water supply-demand within a catchment. The most important elements of water sustainability in a region are its water supply-demand, environmental, and socio-economic attributes. In this paper, an index called PI-Plus (P for Paydari as it is an indigenous term for sustainability) is extended, and its interdependencies with another index called sustainability group index are taken into account. A water balance platform is used that utilizes hydrologic cycle attributes and could be considered as a systems approach to sustainability evaluation. A hypothetical case study is selected that has the components of a real-world problem. A time series of water balance data is synthesized by utilizing basic climatic and hydrologic data from a real watershed. This could be considered as a contribution and a practical engineering solution to generate water balance data in the developing regions. PI-Plus consists of five indicators representing the estimations of gross annual available water (using the physical input-output table approach), economic efficiency of delivered water, system's performance in the context of reliability of supply, and maintaining aquifer storage and river instream flow requirements. Furthermore, a framework for considering a new 5th indicator for social aspects is developed by employing the Nash bargaining theory. Unlike many previous studies of water-related indices, a platform is developed that can fine-tune the assessment of water system performance of different elements and components in a watershed and water cycle scale. Then, by applying uncertainty analysis, the margins of errors in estimating the indicators are determined. The results also present the extent of indicators' improvement that could be achieved. This study could provide a basis for water balance studies and the implementation of different triggers that are socially sensitive and technically feasible to measure sustainability in the developing regions.