An improved eco-flow metrics and its interpretability for urban rivers: quantifying by the environmental flow components using SHAP

Diagram linking EFCs to IEFM (EUI, eco-surplus, eco-deficit) with SHAP importance and time-series summaries. Urbanization and interbasin water transfers are among the most profound human-induced drivers altering natural hydrological regimes. However, compared with urbanization, the ecological impacts of inter-basin water transfers remain insufficiently quantified. This study develops an improved eco-flow metrics (IEFM) by embedding a novel eco-uniformity indicator (EUI) into eco-flow metrics (EFM) based on the flow duration curve (FDC). Furthermore, a SHapley Additive exPlanations (SHAP)-based interpretability framework is employed to systematically quantify the contributions of environmental flow components (EFCs) to IEFM variations. This framework is applied to the Xiaoqing River, Jinan, China, with 60 years (1961–2020) of daily flow records. The results indicate that urbanization and water diversion have led to an increasingly concentrated distribution of the flow regime, reducing flow diversity. SHAP analysis emphasizes that the duration and frequency of low and high flow pulses, as well as the peak flow of small floods, are the main flow components shaping IEFM. Notably, although extremely low-flow events became less prevalent in the latter two periods, they remained an influential contributor to IEFM. By integrating IEFM with interpretable EFC analysis, this study offers a more robust basis for ecological scheduling and adaptive river management under ongoing anthropogenic pressures.