High frequency dataset for event-scale concentration-discharge analysis in a forested headwater 01/2018-08/2023

This composite repository contains high-frequency data of discharge, electrical conductivity, nitrate-N, DOC and water temperature obtained the Rappbode headwater catchment in the Harz mountains, Germany. This catchment was affected by a bark-beetle infestion and forest dieback from 2018 onwards.The data extents previous observations from the same catchment (RB) published as part of Musolff (2020).
Details on the catchment can be found here: Werner et al. (2019, 2021), Musolff et al. (2021).
The file RB_HF_data_2018_2023.txt states measurements for each timestep using the following columns: \"index\" (number of observation),\"Date.Time\" (timestamp in YYYY-MM-DD HH:MM:SS), \"WT\" (water temperature in degree celsius), \"Q.smooth\" ( discharge in mm/d smoothed using moving average), \"NO3.smooth\" (nitrate concentrations in mg N/L smoothed using moving average), \"DOC.smooth\" (Dissolved organic carbon concentrations in mg/L, smoothed using moving average), \"EC.smooth\" (electrical conductivity in µS/cm smoothed using moving average); NA - no data.

Water quality data and discharge was measured at a high-frequency interval of 15 min in the time period between January 2018 and August 2023. Both, NO3-N and DOC were measured using an in-situ UV-VIS probe (s::can spectrolyser, scan Austria). EC was measured using an in-situ probe (CTD Diver, Van Essen Canada). Discharge measurements relied on an established stage-discharge relationship based on water level observations (CTD Diver, Van Essen Canada, see Werner et al. [2019]). Data loggers were maintained every two weeks, including manual cleaning of the UV-VIS probes and grab sampling for subsequent lab analysis, calibration and validation.

Data preparation included five steps: drift corrections, outlier detection, gap filling, calibration and moving averaging:
- Drift was corrected by distributing the offset between mean values one hour before and after cleaning equally among the two weeks maintenance interval as an exponential growth.
- Outliers were detected with a two-step procedure. First, values outside a physically unlikely range were removed. Second, the Grubbs test, to detect and remove outliers, was applied to a moving window of 100 values.
- Data gaps smaller than two hours were filled using cubic spline interpolation.
- The resulting time series were globally calibrated against the lab measured concentration of NO3-N and DOC. EC was calibrated against field values obtained with a handheld WTW probe (WTW Multi 430, Xylem Analytics Germany).
- Noise in the signal of both discharge and water quality was reduced by a moving average with a window lenght of 2.5 hours.

References:
Musolff, A. (2020). High frequency dataset for event-scale concentration-discharge analysis. https://doi.org/http://www.hydroshare.org/resource/27c93a3f4ee2467691a1671442e047b8
Musolff, A., Zhan, Q., Dupas, R., Minaudo, C., Fleckenstein, J. H., Rode, M., Dehaspe, J., & Rinke, K. (2021). Spatial and Temporal Variability in Concentration-Discharge Relationships at the Event Scale. Water Resources Research, 57(10).
Werner, B. J., A. Musolff, O. J. Lechtenfeld, G. H. de Rooij, M. R. Oosterwoud, and J. H. Fleckenstein (2019), High-frequency measurements explain quantity and quality of dissolved organic carbon mobilization in a headwater catchment, Biogeosciences, 16(22), 4497-4516.
Werner, B. J., Lechtenfeld, O. J., Musolff, A., de Rooij, G. H., Yang, J., Grundling, R., Werban, U., & Fleckenstein, J. H. (2021). Small-scale topography explains patterns and dynamics of dissolved organic carbon exports from the riparian zone of a temperate, forested catchment. Hydrology and Earth System Sciences, 25(12), 6067-6086.