README for dataset: 4DHydro Benchmark Dataset wflow_sbm

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# Contact information
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Authors: Imhoff, R.O. & A.H. Weerts
Affiliation: Operational Water Management & Early Warning, Department of Inland Water Systems, Deltares, Delft, The Netherlands

Corresponding author: Imhoff, R. (Ruben)
Ruben.Imhoff@deltares.nl

Corresponding author: Weerts, A. (Albrecht)
Albrecht.Weerts@deltares.nl

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# General dataset information
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This readme.txt file describes the contents of the data package associated with the ESA 4DHydro project (https://www.ufz.de/index.php?en=50452) working package 5. 4DHydro working package 5 is dedicated to provide a set of land-surface and hydrological model community experiment outputs. The experiments contain a set of hydrological simulation outputs from various land-surface and hydrological models that are forced with the same meteorological forcing. Experiment 1.0 is the benchmark of the models without any further calibration. Experiments 2.x - 4.x contain the results of the calibrated/optimized models, where (earth) observation products are used as information for the calibration/optimization process. 

This datapackage contains the outputs from WP5 experiment 1.0 for the wflow_sbm hydrological model (van Verseveld et al., 2022; https://www.deltares.nl/en/software-and-data/products/wflow), which was developed at Deltares, for the test period 1990 - 2021 for the 4DHydro benchmark regions Europe, Rhine, Po and Tugela. The model is forced with the EMO-1 meteorological forcing (https://data.jrc.ec.europa.eu/dataset/0bd84be4-cec8-4180-97a6-8b3adaac4d26), using the Hargreaves method to determine the potential evaporation (a required variable for wflow_sbm). The output consists of the model variables discharge, soil moisture, evapotranspiration and total water storage for these regions at three different model resolutions: 30 arcsecond (approximately 1 km), 2 arcminutes (approximately 4 km) and 4 arcminutes (approximately 8 km). See https://opensciencedata.4dhydro.eu/ for a STAC catalog with links to outputs from other models. Outputs are formatted according to the 4dHydro working package 2 storage protocol (Droppers & Rakovec et al., 2024).

For more information about the model derivation and setup, we refer the reader to the references below. 


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# File type
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netCDF-4 (.nc), and stored as a zipped file per region (Europe, Rhine, Po and Tugela), spatial resolution (30 arcsec, 2 arcmin and 4 arcmin), variable (soil moisture, discharge, evapotranspiration and total water storage) and month.
Note that the NetCDF-4 files also contain their own meta-information, which can be accessed using, for example, ncdump (www.bic.mni.mcgill.ca/users/sean/Docs/netcdf/guide.txn_79.html).


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# Data specific information
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Data type: Float
Dimensions: time, latitude, longitude
Spatial resolution: 30 arcsecond (approximately 1 km), 2 arcminutes (approximately 4 km) and 4 arcminutes (approximately 8 km)
Temporal resolution: daily
Temporal coverage: 1990 - 2022
Projection: WGS84

Folder Structure
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Each subfolder contains the data for a different region extent (Rhine, Po and Tugela). 

wflowsbm_era5_rhine_30sec
- Number of rows: 840 (30 arcsec), 210 (2 arcmin), 105 (4 arcmin)
- Number of columns: 1200 (30 arcsec), 300 (2 arcmin), 150 (4 arcmin)
- Extent in lat-lon: 53, 3 [ULC]; 53, 13 [URC]; 46, 3 [LLC]; 46, 13 [LRC]
wflowsbm_era5_po_30sec
- Number of rows: 480 (30 arcsec), 120 (2 arcmin), 60 (4 arcmin)
- Number of columns: 840 (30 arcsec), 210 (2 arcmin), 105 (4 arcmin)
- Extent in lat-lon: 47, 6 [ULC]; 47, 13 [URC]; 13, 6 [LLC]; 43, 13 [LRC]
wflowsbm_era5_tugela_30sec
- Number of rows: 360 (30 arcsec), 90 (2 arcmin), 45 (4 arcmin)
- Number of columns: 480 (30 arcsec), 120 (2 arcmin), 60 (4 arcmin)
- Extent in lat-lon: -27, 28 [ULC]; -27, 32 [URC]; -30, 28 [LLC]; -30, 32 [LRC]

Folder contents
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The folders contain the wflow_sbm model outputs (discharge, evapotranspiration, soil moisture and total water storage). Furhtermore, all folders contain the simulation mask for the river catchment and the catchment upstream area for each cell.

Variables and units: 
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Output variables were abbreviated in the outputs.

name	description					units
q		discharge					m3 s-1
et		evapotranspiration			kg m-2 s-1
sm		soil moisture				volumetric %
tws     total water storage         kg m-2
mask	catchment mask				0 or 1
uparea	catchment upstream area		m2


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# Obtain download URLs
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The following script can be used to obtain a list of download URLs, that can be used with e.g. wget, from the 4DHydro results per model, catchment and experiment: https://codebase.helmholtz.cloud/4dhydro/wp2/benchmark/-/tree/main/scripts/download?ref_type=heads.

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# License
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CC BY-NC 4.0


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# References
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- van Verseveld, W. J., Weerts, A. H., Visser, M., Buitink, J., Imhoff, R. O., Boisgontier, H., Bouaziz, L., Eilander, D., Hegnauer, M., ten Velden, C., and Russell, B. (2022). Wflow_sbm v0.6.1, a spatially distributed hydrologic model: from global data to local applications. Geoscientific Model Development Discussions. https://doi.org/10.5194/gmd-2022-182, accepted for publication.  
- Imhoff, R. O., van Verseveld, W. J., van Osnabrugge, B., and Weerts, A. H. (2020). Scaling point-scale (pedo) transfer functions to seamless large-domain parameter estimates for high-resolution distributed hydrologic modeling: An example for the Rhine River. Water Resources Research, 56, e2019WR026807. https://doi.org/10.1029/2019WR026807  
- Eilander, D., van Verseveld, W., Yamazaki, D., Weerts, A., Winsemius, H. C., and Ward, P. J. (2021). A hydrography upscaling method for scale-invariant parametrization of distributed hydrological models. Hydrology and Earth System Sciences, 25, 5287–5313, https://doi.org/10.5194/hess-25-5287-2021 
- Eilander, D., Boisgontier, H., Bouaziz, L. J. E., Buitink, J., Couasnon A., Dalmijn, B., Hegnauer, M., de Jong, T., Loos, S., Marth, I., and van Verseveld, W. (2023). HydroMT: Automated and reproducible model building and analysis. Journal of Open Source Software, 8(83), 4897. https://doi.org/10.21105/joss.04897  
- Droppers, B., Rakovec, O., Avila, L., Azimi, S., Cortes-Torres, N., De León Péréz, D., Imhoff, R., Frances, F., Kollet, S., Rigon, R., Weerts, A., and Samaniego, L. (2024). Hydrological Reference Dataset (Tier 1) for the ESA 4dHydro Open Science Catalogue. Nature Scientific Data, in review.