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Event and base flow in subsurface drainage dataset

Aniekwensi, Emeka Franklin Felix1

Published Jan 09, 2026 on Dryad. https://doi.org/10.5061/dryad.t1g1jwtgs

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Jan 09, 2026 version files 310.83 KB

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Abstract

Accurate separation of Event Flow and Base Flow in subsurface drainage systems is essential for nutrient transport assessment, yet the task remains challenging because both components exit through the same tile network, producing a composite hydrologic signal. This work seeks to establish a standardized, objective, and reproducible method for delineating event and base flow across sites, seasons, and time resolutions. A percentile-based separation framework was developed that applies the 82.5th percentile threshold for wetter seasons such as winter and spring and the 95th percentile for drier seasons such as summer and fall. An event is defined when flow exceeds the seasonal threshold and increases by at least twenty percent from the previous value and ends when flow returns to the threshold for two consecutive time steps. Minimum data requirements of one year for daily datasets and three months for hourly datasets were set to ensure representative flow distributions. A web-based tool was created to implement the framework, calculate event-scale metrics, and generate reproducible event identifiers. The method produced consistent and repeatable separation of event and base flow and removed subjective judgments inherent in existing approaches. Overall, this structured and transparent procedure enhances subsurface drainage event-scale hydrologic assessment and supports improved evaluation of nutrient losses under variable climatic conditions.