Dear colleagues,

Based on our successful experience in establishing the SWIG database on infiltration data, we decided to initiate another project to collect soil hydraulic properties and their metadata. Currently available databases that provide estimates of the soil water retention curve and the hydraulic conductivity curve use pedotransfer functions that do not include information about the structural properties. We are therefore seeking original soil hydraulic data (soil water retention curve, hydraulic conductivity curve, and air permeability) obtained on undisturbed soil samples and their corresponding soil properties (e.g. texture, carbon content, bulk density, taxonomic and land-use information) as well as quantitative and/or qualitative information on the soil structure. These structural data may include:

. Taxonomic information (Blocky, granular, or etc.)

. Ksat on undisturbed soils

. Pore size data (obtained e.g. from nuclear magnetic resonance (NMR) relaxometry)

. Aggregates stability

. Geometric mean or mean weight diameter (GMD or MWD) of aggregates

. Fractal dimension .

. Mechanical resistance or etc.

Any metadata describing the experimental data in more detail are welcomed. Data may stem from lab scale, plot, field and catchment scale experiments. We are planning to establish a database of these data that we will submit to a data journal (e.g. Earth System Data Science or any other suitable journal). In order to honor your support, we would like to include you as co-author on the manuscript. We hope that you will contribute to this initiative and welcome any questions you might have.

Please use the enclosed template file (excel file) to share data with us.

We would also appreciate if you could kindly distribute this request to colleagues that might be interested in contributing to this effort.

Our published article in SWIG database is provided in following link for those people who we have had no luck to have their supports for that project.

Article Development and Analysis of Soil Water Infiltration Global Database

Best regards,

Mehdi Rahmati ([email protected])

Rainer Horn ([email protected] )

Harry Vereecken ([email protected] )

Lutz Weihermüller ([email protected] )