Multicriteria value assessment of alternative water resources: a comparative study on desalinated seawater and potable reclaimed water in Qingdao City

The intensifying global freshwater crisis has amplified the strategic importance of non-conventional water resources (NCWRs), particularly desalinated seawater (DSW) and potable reclaimed water (PRW). Effectively allocating these diverse NCWRs requires balancing ecological protection with economic development. However, the lack of a systematic method for quantifying their multicriteria value across economic-ecological nexuses hinders sound decision-making. Based on emergy theory, this study improves the comprehensive value assessment framework by adding ecological cost value, which is used to assess the multicriteria value of DSW and PRW. The results show that the ecological costs of DSW and PRW were 5.86 × 10¹⁰ and 2.44 × 10¹¹ sej/m³, respectively, which indicates that the impact of emissions on the environment cannot be ignored. The environmental-economic values of DSW and PRW were 4.137 × 10¹² and 4.80 × 10¹³ sej/m³, with cost-effectiveness ratios of 1:0.001 and 1:4.92, respectively. The assessment framework proposed in this study offers a comprehensive approach to water resource valuation, demonstrating the pronounced advantages of PRW over DSW. Additionally, the active promotion of NCWRs utilization and the continued refinement of the management system are crucial for advancing their development. These findings provide policymakers with a scientifically grounded tool to optimize water allocation strategies that balance economic and environmental objectives.