Data and code for: Concentration distributions and delivery timing constrain first-flush capture in agricultural runoff

This record contains the data and Python code supporting the article “Concentration distributions and delivery timing constrain first-flush capture in agricultural runoff” (submitted to Water Research). The study derives two bounds on the share of an event load that a given capture volume can intercept, one set by the event minimum concentration and one by ideal selection of the most concentrated runoff, and uses them to separate weak first flushes limited by the concentration distribution from those limited by delivery timing. Contents: North Wyke Farm Platform (UK), derived event records. Event definitions, screening outcomes, MFF30, the two bounds and diagnostic classes for the sediment and nitrate records of catchments 2, 3, 5 and 8, October 2016 to March 2020 (Supplementary Data S1 of the article). The records were derived from the processed 15-min data of Zhang, Collins and Darch (2024), https://doi.org/10.23637/rothamsted.99117 (CC BY 4.0). Jinxiang (Shandong, China), plot data. Within-event concentrations of suspended solids, TN, TP, NH4+-N and NO3−-N from 12 cropland plots sampled from runoff onset on 12 July 2023, with topsoil properties. Known data-quality issues (apparent suspended solids in direct rain, implausibly low NH4+-N and NO3−-N, COD) are documented in README.md. Rainfall. GPM IMERG V07 extracts for the 12 July 2023 storm and the 2023 wet season. Literature series. 384 within-event concentration series digitised from 15 cropland studies, of which the 231 series from 10 studies that reported runoff rates or volumes were analysed in the article. Code. Python scripts for the North Wyke analysis (event extraction, screening, bounds and classes, robustness, truncation and capture analyses, concentration–discharge estimation), the Bayesian wash-off model for Jinxiang, the literature synthesis and all figures. [Keep only if the zip still contains them:] The archive also contains materials from an earlier version of the analysis (a re-analysis of street wash-off tests, simulated wash-off combinations and microplastic identifications) that are not used in the article.