Global SWOT River Water Surface Slope Observations (2023–2026), Reach-Level Temporal Variability Statistics, and Gauge-Pair Slope Code

This record contains the data and code for Chen et al. (2025). It provides quality-controlled SWOT reach observations of river water surface slope (WSS) worldwide (March 2023 – March 2026), reach-level statistics of WSS temporal variability, and a Python script that computes WSS from pairs of USGS stream gauges. **Files** - **README.md**: overview, processing summary, how to read the data, how to run the code, data sources, and license.- **GlobalWSS_SWOT_reach_observations_QC.parquet**: - quality-controlled per-pass SWOT reach observations (SWOT_L2_HR_RiverSP_D) joined with SWORD v17b reach attributes; - 6,039,429 observations of 155,319 reaches (98 columns).- **GlobalWSS_SWOT_reach_statistics.parquet**: - one row per reach (155,319 reaches, 47 columns): WSS statistics and temporal-variability metrics, including the relative WSS range (P95 − P05)/median; - also includes reach and catchment attributes: dams, climate, population and Köppen–Geiger class.- **GlobalWSS_SWOT_reach_statistics.csv**: CSV copy of the reach statistics table.- **GlobalWSS_data_dictionary.csv**: description, units and source of every column in both tables.- **gauge_pair_wss.py**: - computes WSS at 15-minute and hourly resolution from any upstream/downstream pair of USGS gauges; - converts gauge datums to NAVD88 (NOAA NCAT), takes the along-channel distance from SWORD, and estimates datum uncertainty; - usage and method are documented at the top of the file. **Reference** Chen, Y., Cohen, S., Dhital, S., Devi, D., & Baruah, A. (2025). Spatial and Temporal Variability in Global River Slopes from the Surface Water and Ocean Topography (SWOT) Satellite. **License:** CC BY 4.0. The columns COMID, unitarea and weighted_uparea_km2 are derived from MERIT-Hydro/MERIT-Basins and remain subject to the MERIT-Hydro license (CC BY-NC 4.0 or ODbL 1.0). **Acknowledgement:** This research was supported by the Cooperative Institute for Research to Operations in Hydrology (CIROH) with funding under award NA22NWS4320003 from the NOAA Cooperative Institute Program. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the opinions of NOAA.