This data set provides data of water quality, discharge, driving forces (meteorology and nutrients), and catchment attributes for a set of 1386 German catchments covering a wide range of natural and anthropogenic conditions. The data set is decribed in detail in the data paper "QUADICA v2.0: Extending the large-sample data set for water QUAlity, DIscharge and Catchment Attributes in Germany" accepted in ESSD (Ebeling et al. 2025), and partly by the previous version 1 (Ebeling, et al. 2022). The metadata of the underlying water quality and quantity data base is available at "WQQDB - water quality and quantity data base Germany" (https://doi.org/10.4211/hs.a42addcbd59a466a9aa56472dfef8721)

Data acknowledgement/citation: We urge the users to also cite relevant data sources of individual components included in QUADICA, when using them. For example, Batool et al. 2022 for the N surplus time series.

This repository includes:

Data files:
1.) Water quality time series as annual medians (c_annual.csv)
2.) Water quantity time series as annual medians of observed discharge time series (q_annual.csv)
3.) Monthly medians and percentiles over the whole time series of water quality variables and discharge (c_q_avg_months.csv)
4.) Monthly and annual time series of median concentrations, flow-normalized concentrations, discharge-weighted concentrations, and mean fluxes estimated using Weighted Regressions on Time, Discharge, and Season (WRTDS) for stations with high data availability (for details see the corresponding paper Ebeling et al.; wrtds_monthly.csv, wrtds_annual.csv), as well as summary statistics with availability and performance of WRTDS models (wrtds_summary.csv).
5.) Meteorological time series as monthly median average temperatures and sums of precipitation and potential evapotranspiration (climate_monthly.csv)
6.) Diffuse nutrient surplus and point source input times series for Nitrogen and Phosphorus (input_N_P.csv)
7.) Summary statistics for the stations including number of samples, covered time periods, degree of censoring (concentrations below the detection limit), outliers (metadata_c.csv).
8.) Metadata with River name, availability of discharge data and information on matching of QUADICA water quality stations with CAMELS-DE and Caravan-DE water quantity stations (metadata_q.csv).
9.) Catchment attributes describing land use, topography, hydroclimate, etc. (attributes.csv).
10.) GIS: delineated catchments (catchments.shp), stationsmoved to the flow accumulation grid (stations_mod.shp), stations with original locations (stations.shp), and files used for topographic catchment delineation. For details refer to the data paper of QUADICA version 1.
11.) Lookup table for merged time series from neighbouring stations (metadata_merge_stations.csv).

Documentation files:
10.) Documentation with description of all data tables (Metadata_QUADICA_v2.pdf).

App for visualization:
11.) Shiny app for visual exploration of QUADICA, follow the readme.txt to run it.

Licenses: The data use licenses of the original data sets apply.

Note that the provided data were created with greatest care, but we cannot guarantee correctness of the data.

Reference to the data description papers:
Ebeling, P., Kumar, R., Lutz, S. R., Nguyen, T., Sarrazin, F., Weber, M., Büttner, O., Attinger, S., and Musolff, A.: QUADICA: water QUAlity, DIscharge and Catchment Attributes for large-sample studies in Germany, Earth Syst. Sci. Data, 14, 3715–3741, https://doi.org/10.5194/essd-14-3715-2022, 2022.
Ebeling, P., Hubig, A., Wachholz, A., Scharfenberger, U., Haug, S., Nguyen, T., Sarrazin, F., Batool, M., Musolff, A. & Kumar, R.: QUADICA v2: extending the large-sample data set for water QUAlity, DIscharge and Catchment Attributes in Germany. Earth System Science Data, 18(1), 691-712, https://doi.org/10.5194/essd-18-691-2026, 2026

CHANGELOG:
11/2026:
- Data quality control from raw data to preprocessed data on the sample level was revised due to recognized inconsistencies in data readings in some federal states.
- Water quality samples from various variables and stations were affected, resulting in changes to the following files: metadata_c, c_annual.csv, c_q_avg_months.csv, wrtds_annual.csv, wrtds_monthly.csv, and wrtds_summary.csv.
- Metadata about merged stations was added. The stations were co-located and time series checked. "Station1" etc. provides the original station name, "Station_merge" is the newly created station name and OBJECTID_merge the OBJECTID as used in other metadata and data table files (the same station merges were already used in QUADICA version 1, now the merging was redone for version 2)