DOI: 10.5061/dryad.t1g1jwtgs
title: Event and base flow in subsurface drainage dataset

description: 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.
description: ## Event and Base Flow in Subsurface Drainage Dataset **Access this
 dataset on Dryad** This dataset contains simulated subsurface drainage
 discharge data used to characterize event flow and baseflow dynamics under
 long-term hydroclimatic conditions. The data were generated using
 continuous hydrologic simulation to evaluate drainage responses to
 precipitation events and groundwater contributions in a humid,
 subsurface-drained agricultural setting. --- ## Description of the Data
 and File Structure This dataset consists of three comma-separated value
 (CSV) files derived from a single long-term subsurface drainage
 simulation. Files are structured to support analysis of drainage discharge
 at hourly and daily temporal resolutions and to facilitate testing,
 validation, and reuse of event–baseflow separation approaches. --- ##
 Files Included in This Dataset ### **DRAINMOD_TEST_DATA.csv** Contains
 continuous simulated subsurface drainage output generated using the
 DRAINMOD model. This file represents the complete simulation record and
 serves as the primary dataset for event and baseflow classification
 analyses under fixed soil, crop, climate, and drainage conditions. ###
 **Random_Daily_Data_Sample.csv** A daily-resolution subset randomly
 sampled from the full simulation period. This file is intended for
 exploratory analysis, methodological testing, and demonstration of
 daily-scale event and baseflow separation without requiring the full
 dataset. ### **Random_Hourly_Data_Sample.csv** An hourly-resolution subset
 randomly sampled from the full simulation output. This file preserves
 short-term hydrologic variability and is suitable for examining event
 timing, peak drainage response, and fine-scale separation of event flow
 and baseflow. --- ## Relationships Between Files All three files originate
 from the same simulated hydrologic system and share identical variable
 definitions, units of measurement, and classification logic. The daily and
 hourly sample files are direct subsets of the full simulation output and
 are provided to support rapid testing, reproducibility, and educational
 reuse. --- ## Simulation Settings and Assumptions ### Weather and Climate
 Inputs * Daily historical precipitation and potential evapotranspiration
 data from Plymouth, North Carolina * Continuous simulation period from
 January 1, 1951 through December 31, 1990 ### Soil Parameters * Portsmouth
 E soil profile with layer-specific hydraulic properties * Saturated
 hydraulic conductivity: 2.5 cm day⁻¹ * Initial water table depth: 50 cm
 below the soil surface * No deep seepage or lateral groundwater inflow
 assumed ### Drainage System Configuration * Drain depth: 1.0 m below the
 soil surface * Drain spacing: 20 m * Conventional subsurface drainage
 layout ### Crop and Management Conditions * Continuous corn production
 throughout the 50-year simulation * No additional management practices
 beyond standard DRAINMOD defaults These assumptions were selected to
 represent a typical subsurface-drained agricultural field in a humid
 region and to enable consistent evaluation of long-term event flow and
 baseflow behavior. --- ## Variables and Definitions All variables are
 consistently defined across files. Units are provided to ensure direct
 interpretation and reuse. ### **(Essential model Data)** ### **Date** Date
 and time of each observation. * Format: MM/DD/YYYY (daily files) or
 MM/DD/YYYY HH:MM (hourly files) ### **Flow** Simulated subsurface drainage
 discharge rate. * Units: depth/day (cm/day) * Represents the volumetric
 flow of water exiting the subsurface drainage system ### **Concentration**
 This tells the concentration of the nutrient exiting the drainage pipe
 (eg. Nitrogen, Phosphorus e.t.c) * Units: milligram/L (mg/L) It is
 important to note that if you do not have concentration data, you can
 populate this cell by 1. 
 
 ## **Additional data set (not essential for performing event Analysis)**
 ## **Water table** Simulated depth to the water table measured below the
 soil surface. * Units: centimeters (cm or m) * Positive values indicate
 depth below the soil surface and negative values will be ponding *
 Represents water table position influencing event flow contributions
 (shallower water tables are observed during events) ### **temperature**
 Soil water temperature, this helps us get the average soil temperature
 during events. * Units: degrees Celsius (°C) ### ### **resolution** all
 data resolution should be consistent and either be in hourly or Daily
 resolution. * Values: `hourly` or `daily` ### **missing_data** Missing or
 invalid observations. * Represented as blank cells * No inputed values are
 included --- ## Definitions of Hydrologic Terms **Event Flow**\ Periods of
 elevated subsurface drainage discharge primarily driven by
 precipitation-related inputs such as rainfall or snowmelt. **Baseflow**\
 The sustained component of drainage discharge supplied mainly by
 groundwater contributions outside of storm-driven periods. **Event
 Period**\ A time interval classified as event flow, beginning when
 discharge exceeds a defined threshold and ending when discharge returns to
 baseline conditions. **Baseflow Period**\ A time interval during which
 discharge remains below the event threshold and reflects
 groundwater-dominated drainage conditions. **Event Threshold**\ A
 discharge magnitude or rate-of-change criterion used to distinguish event
 flow from baseflow. Thresholds were determined using consistent,
 site-specific hydrologic criteria applied uniformly across the dataset.
 --- ## Sharing and Access Information This dataset is publicly available
 through the Dryad Digital Repository. * Dataset DOI:
 [https://doi.org/10.5061/dryad.t1g1jwtgs](https://doi.org/10.5061/dryad.t1g1jwtgs) * Repository: Dryad No additional external data sources are required to use this dataset. --- ## Code and Software No executable scripts are included in this submission. All files are provided in CSV format. Compatible software includes: * Microsoft Excel or equivalent spreadsheet software * R, Python, MATLAB, or other statistical and scientific computing environments capable of reading CSV files --- ## Dataset Readiness Statement All variables are explicitly defined with units of measurement and consistent interpretation across files. The dataset is fully documented to support transparency, reproducibility, and reuse in hydrologic, agricultural drainage, and environmental modeling research.