Investigating the intercorrelations of ecosystem services related to water resources at the catchment scale

Ecosystems provide various direct and indirect benefits for human society, which are closely intertwined with human life, health, and economic well-being. However, pressures such as climate change, changes in land use/land cover, and human activities may pose threats or undermine the stability of ecosystems, consequently impacting the provision of ecosystem services. In recent years, climate change has altered precipitation patterns and increased the occurrence of extreme weather events, resulting in variations in watershed dynamics and affecting the stability of water resources. The impact on water resources has intensified, leading to changes in watershed ecosystem services and influencing the quality of human life and property security. This study is based on simulations using the Soil and Water Assessment Tool (SWAT) model in the Jhuoshuei River basin. Simulations cover historical periods (2002-2020) and near-future (2021-2040) and far-future (2081-2100) scenarios under RCP2.6 and RCP8.5 of CMIP5 models. Five indicators, which include freshwater provision index (FPI), green water scarcity (GWS), green water vulnerability (GWV), flood regulation index (FRI), and erosion regulation index (ERI), were selected for quantitative assessment and analysis of dry and wet season water provisioning and regulating services in the Jhuoshuei River basin. Spatial autocorrelation analysis was employed to identify high and low zones of ecosystem services, and Spearman correlation analysis was used to determine the trade-offs and synergies among the five ecosystem services indicators. The results indicate significant differences in the five indicators between dry and wet seasons. The FPI performs better in the wet season, while the other four indicators exhibit better performance in the dry season. Across historical and climate change scenarios, the relationships among the five indicators remain consistent. The FPI demonstrates a trade-off relationship with the other four ecosystem services, while the FRI, ERI, GWS, and GWV exhibit mutual synergies. This study shows the intercorrelations among the ecosystem services related to water resources, and the results serve as the references for water resources regulations and watershed management.

Keywords: SWAT model, Provisioning services, Regulating services, Green water security, Jhuoshuei River basin