UK-Flow15: Sub-hourly river flow data observations from 1369 river gauges in the UK, 1948-2023

High-resolution (15-min) river flow records date back almost a century in the UK. Nevertheless, these data have historically been used only in small-scale studies or operational contexts. A key reason for this limited applicability is that, unlike rainfall, which benefits from established national sub-daily products that are easily accessible (e.g. CEH-GEAR1hr and GRaD-GB), no equivalent unified sub-daily flow product has been available at the national scale. At the same time, the rapid growth of large-sample studies has transformed the field of hydrology, enabling insights into spatial patterns, flood-generating mechanisms and assessing model performance across regions. However, most large-sample hydrological datasets still rely on daily series, whose coarse temporal resolution is insufficient to represent flood-event dynamics, which often unfold on sub-daily timescales.

The creation of UK-Flow15 (available at https://doi.org/10.5285/211710ac-f01b-4b52-807f-373babb1c368) is motivated by these two limitations: the absence of a national high-resolution flow dataset for the UK and the clear scientific value enabled by large-sample analyses. The new national-scale 15-minute dataset comprises >1.8 billion observations from 1,369 gauging stations, spanning 1948–2023.

Producing UK-Flow15 required extensive harmonisation, metadata reconciliation and cross-checks to resolve structural inconsistencies. Historically, the 15-minute records received far less attention than the daily and AMAX datasets derived from them, leaving the high-resolution series inconsistently digitised, stored in multiple versions and rarely subjected to the same level of quality control or metadata curation.

Furthermore, to ensure the dataset is FAIR, we developed and applied a comprehensive quality-control procedure designed to inform users about data quality and limitations. Flagging involved manual visual inspection of all stations, consistency checks against other UK hydrological products, and automated detection of common anomalies such as spikes, truncations, discontinuities, fluctuations and other artefacts. Additional high-flow checks assess the plausibility of extreme events by comparing them with rainfall at the location and concurrent flows in nearby catchments, highlighting cases where they may be hydrologically inconsistent.

UK-Flow15 and its QC framework form a robust standalone product, providing trustworthy, well-documented sub-hourly flow data. Beyond this, the dataset supports the enhancement of other large-sample products, including CAMELS-GB v2. Additionally, the QC system is also adaptable, offering a methodology that can be extended to the creation of other sub-daily/hourly hydrological datasets.

In this work, we aim to demonstrate how UK-Flow15 was processed, what data it contains and how it can be used. We outline the harmonisation and QC workflow applied to produce consistent national 15-minute records. We present the complete flow series, QC flags and metadata now openly accessible. We highlight applications for large-sample studies, flood-wave characterisation and hydrological model evaluation. We hope the dataset contributes to better-informed decisions on sub-daily flood processes at large scale.