Derived datasets for the Han River four-layer diagnostic framework

De-identified derived datasets supporting all main-text and supplementary figures and tables for the Water Resources Research manuscript on engineering superposition and water-quality diagnostics in the middle–lower Han River. Contents: • Supplementary Tables S1–S3 and ED Tables 1–3 • Spatial DiD full-model summary • Flow-quartile correlation matrices (Fig. 6a) • Q1 low-flow scatter plot subsets (Figs. 5, S5) • Dry-season pre/post discharge summaries (Fig. 6b) • Layer 1 anomaly scores and pre/post period means • Layer 2 spatial DiD results • Impoundment level-differential and hydro period means (Figs. 7a–7b) • Station metadata (locations, coverage summary, engineering exposure groups) NOT included (restricted by data-provider agreements): • Complete 10-station monthly water-quality time series (DO, CODMn, COD, NH3-N, TP) • Complete main-station monthly discharge archive (Huangzhuang) These derived files are sufficient to reproduce aggregated statistics and figure layouts. Full reproduction of raw-data-dependent panels requires restricted data obtained from: • Hubei Provincial Ecological and Environmental Monitoring Centre (water quality) • Changjiang Water Resources Commission (discharge and stage) Companion analysis code is archived separately on Zenodo (see Related identifiers).