Assessment of Sustainable Water Management Strategies in Porsuk Watershed Using Hydrological WEAP Model

Natural resources are under significant pressures, such as increasing population, consumption patterns, land use changes and global warming. Neglecting the pressures and the interactions of resources increases the competition between urban, agricultural and industrial sectors. In addition, water stress affects ecosystem functionality, economic development and social equity. Thus, it is essential to develop integrated water management alternatives considering various objectives. Sustainable approaches should support the success of long-term policies while reducing environmental risks. One of them, the Circular Economy (CE) aims to minimize the gap between supply and demand across the sectors and can be effective in sustainable future development. The Porsuk Watershed in Türkiye is a semi-arid region covering an area of 10,825 km². The watershed hosts a rich biodiversity while anthropogenic activities pose a threat to ecosystem services. The Porsuk Stream, a tributary of the Sakarya River, has a length of 448 km and is the main source of urban water supply, irrigation water and industrial production. In addition, there is a significant dependence on groundwater across the sectors. The aim of this study is to assess strategies of sustainable water resources management to enhance security and reliability by comparing the performances of Circular Economy models such as Reduce, Reuse, Recycle and Replenish. Thus, understanding the complex synergistic and trade-off relationships in resource management within the watershed will contribute to stakeholders in the decision-making process. A hydrological model of the Porsuk stream is created using Water Evaluation and Planning System (WEAP) software between 2004-2022. The most preferred water allocation alternatives are selected according to environmental and economic indicators using Multi-Criteria Decision Making (MCDM) methods. Scenarios are performed at multiple demand sites in the hydrological model. Accordingly, Reduce alternatives helps to reduce water deficit levels and affect water allocation in the watershed. With the Reuse, Recycle and Replenish scenarios, pressures of agriculture and industry sectors on the groundwater aquifer are mitigated. In addition, the change in environmental flows is compared according to business-as-usual (BAU) and different scenario combinations.