Resumen
Despite being a limited resource, pollution, poor management, and other drivers like climate change make available water unsuitable and insufficient for human consumption and ecosystem maintenance. Therefore, a transdisciplinary approach is needed for managing this precious resource. The overall aim of this paper is to address water inequalities and improve human well-being using an integrated approach of key informant interviews, hydrological modeling, and the payment of ecosystem services (PES) scheme in Pinglin District, Taiwan. This site is an upstream area of Feicui Reservoir, which protects the downstream tap water supply. Key informant interviews were conducted to identify the gaps in and challenges to water resource management. This was followed by a scenario-based hydrological simulation using a Water Evaluation and Planning (WEAP) tool to project future water quality by the year 2050 (using biochemical oxygen demand and total coliform content as key indicator parameters) and to trace the factors responsible for water pollution. Survey analysis of key informant interviews depicts that this area is facing several challenges, such as lack of water infrastructure, agricultural subsidy, construction restrictions, etc., which cumulatively cause water scarcity in the upstream regions. On the other hand, hydrological simulation results show that population decline and climate change under an RCP 8.5 scenario will have an enormous negative impact on water quality. The concentrations of BOD and E. coli in river water will expand by 110.1% and 117.3%, respectively, by 2050 compared to 2018. Finally, the results of the study suggest that the PES scheme can play a positive role in enabling integrated water resource management. For example construction of a small-scale wastewater treatment plant in the upstream area will reduce the total E. coli concentration by up to 90%. While the initial cost of construction will be taken care of by the government, the operation and management cost of this infrastructure will be covered by people living downstream, who need to pay only $0.10 per year per person. The obtained results should be vital for both the stakeholders and decision-makers in this region.