A Sustainability Assessment Framework for Decentralized Water Systems in the GCC Region: A Systematic Review and Delphi Study

Abstract

Water management in Arid and Semi-Arid Regions (ASARs), specifically in the Gulf Cooperation Council (GCC) countries, has historically relied on large-scale, centralized systems that have successfully expanded potable water access. However, their high energy intensity, escalating operating costs, and limited flexibility amid increasing climate variability have raised concerns about their long-term sustainability. In this context, decentralized water systems (DWSs), including rainwater harvesting (RWH), greywater reuse (GWR), and hybrid rainwater–greywater systems (HRGSs), offer promising solutions to reduce pressure on centralized infrastructure, enhance dry-season water availability, and mitigate urban flooding risks. Despite their strategic relevance, a comprehensive sustainability assessment framework tailored to GCC conditions remains insufficiently developed. To address this gap, a systematic review of literature indexed in Scopus, Engineering Village, and Google Scholar was conducted. Thirty studies met the inclusion criteria and were critically analyzed to identify prevailing assessment approaches and recurring sustainability dimensions. Building on these findings, this study proposes a regionally tailored, multi-criteria sustainability framework designed specifically for GCC contexts. The proposed framework integrates five core dimensions, including technical, environmental, economic, social, and political–institutional, comprising 14 indicators and four sub-indicators. To refine and validate the framework, a two-round Delphi technique was conducted. A total of 102 experts from GCC member states were invited, of whom 43 participated in the first round, and 25 completed the second round. The results demonstrated strong consensus regarding the relevance and applicability of the selected indicators, with particular emphasis on technical and environmental dimensions. Notably, the lack of agreement on equal weighting in the first round justified the adoption of a ranking-based weighting approach in the second round, enabling a more realistic representation of expert consensus. The final DWS index, developed using a hierarchical multi-criteria decision analysis (MCDA) approach, integrates criterion weights, indicator weights, and performance scores into a single composite metric. The results indicate that HRGSs achieved the highest overall performance (55.00), followed closely by GWR (54.76) and RWH (54.20). Overall, the proposed framework provides a robust and context-specific tool to support sustainability assessment and inform policy development for DWSs in the GCC region.