Feasibility of Clean Water Supply in a Tropical City: Case Study of Kediri

The availability of clean water is fundamental to sustainable urban development, particularly in tropical cities experiencing rapid population growth and increasing water demand. Although previous studies have examined water demand forecasting or raw water availability independently, integrated feasibility assessments remain limited for medium-sized tropical cities. This study evaluated the feasibility of long-term clean water supply in Kediri City, Indonesia, by integrating population projection, water demand forecasting, water balance analysis, and raw water source assessment through 2043. Population projections were developed using arithmetic, geometric, and least-squares methods, while water balance analysis was employed to compare projected demand with existing water availability. The results indicate that the maximum daily water demand will reach 618.52 L s⁻¹ by 2043, substantially exceeding the current production capacity of Tirta Dhaha Regional Drinking Water Company (228 L s⁻¹). Among the evaluated alternatives, the Brantas River demonstrated the greatest potential as a sustainable raw water source owing to its high discharge capacity. Comparative analysis with the Langat, Conchos, Mekong, and Mahaweli river basins further emphasizes the importance of integrated river basin management through institutional coordination, upstream conservation, and adaptive monitoring. These findings provide a scientific basis for diversifying raw water sources and strengthening long-term water supply planning in medium-sized tropical cities facing increasing urbanization and climate crisis, while future studies should incorporate climate and demographic uncertainties.