Quantifying Temporal Shifts in Catchment Water Storage Using a Time-Varying Budyko Framework in Taiwan

   As the impacts of climate change intensify and water demand continues to increase, assessing future water resources has become an important issue. In Taiwan, the precipitation–runoff relationship exhibits a decoupled behavior. Although annual precipitation has increased in most catchments, the corresponding increase in runoff has been smaller than expected or has even declined.

  A parametric Budyko framework was employed to quantify the temporal evolution of 54 catchments across Taiwan in Budyko space from 1970 to the present. The results indicate that Budyko curves constructed using 11-year moving windows provide a robust representation of long-term catchment water balance behavior. Moreover, the catchment landscape parameter (m value) shows an increasing trend over time in most Taiwan’s catchments, implying a gradual enhancement of catchment water storage capacity. This finding suggests that assuming a fixed m value for future runoff may lead to overestimation.

  To better understand the drivers of changes in m, this study explores the relationships between variations in m and changes in soil moisture, land use, groundwater levels, and streamflow. By capturing the temporal dynamics of the catchment landscape, this approach aims to improve the robustness of future water resource assessments based on the Budyko framework.