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GEWEX-SoilWat Initiative

SoilWat is a joint project between the Global Energy and Water cycle Exchanges (GEWEX), a World Climate Research Programme (WCRP) Core Project and the International Soil Modeling Consortium (ISMC).



  1. SoilWat
  2. Participants
  3. GEWEX
  4. Activities
  5. Goals
  6. Publications


The Soil and Water (SoilWat) Initiative brings together two research communities to improve the representation of soil and subsurface processes in climate models. The soil and groundwater community and the climate modeling community (the latter represented by GEWEX) are working together to identify the most pressing challenges and topics related to this effort.

Figure above: Participants of the GEWEX GLASS 2019 meeting on evapotranspiration

Figure above: Participants of the 1st GEWEX SoilWat Planning Workshop 2016

GEWEX is dedicated to understanding Earth’s water cycle and energy fluxes at the surface and in the atmosphere. GEWEX comprises a global network of scientists gathering information on and researching the global water and energy cycles, which will help to predict changes in the world’s climate. The International GEWEX Project Office, or IGPO, supports these activities by planning meetings, implementing research goals, and producing a quarterly newsletter to keep the GEWEX community informed.

SoilWat partners identified three main initiatives at the 1st GEWEX SoilWat Initiative Planning Workshop held during June 2016, in Leipzig, Germany. A report on the workshop detailing discussions and outcomes is available here.

The first initiative is a joint GEWEX and International Soil Modeling Consortium (ISMC) activity to conduct an in-depth survey on how key soil physical processes (water and heat flow) are represented in climate and hydrological models. The second inititative is a systematic assessment of the quality of resolved soil maps used in climate modelling, and the effect of different soil maps on the prediction of land surface fluxes and state variables. This activity also aims to improve the quality and resolution of soil maps. The third activity involves conducting a survey of whether and how groundwater is implemented in climate models and the development of strategies for better incorporation of groundwater in climate models.  The ultimate aim is for the various research communities to jointly develop a global groundwater monitoring system, which will involve a combination of observations (in-situ and remote sensing), modelling and data-assimilation.

Planned activities related to the three initiatives include:

  • •    Establishing a survey of existing soil models in land surface models
    •    Surveying the pedotransfer functions that are used in global climate models
    •    Carrying out model sensitivity analyses
    •    Conducting a soil parameter Model Intercomparison Project (MIP)
    •    Seeking or developing a modeling case study in which several soil models are run to model fluxes (of mass and energy) that are relevant for climate models
    •    Establishing a global database for historical and current groundwater levels.

The GEWEX SoilWat Initiative welcomes collaboration, so if you are interested in any of these efforts, please contact the International GEWEX Project Office at or one of the organizers (Dani OrAnne Verhoef, and Matthias Cuntz) directly.


List of Working Group Goals:

  • Surveying and comparing the hydraulic pedotransfer functions that are used in global climate models
  • Carrying out a sensitivity analysis of the effect of these different functions on the water balance  
  • Conducting a soil parameter MIP, globally with a number of key land surface models
  • Surveying and comparing the thermal pedotransfer functions and key equations that are used in global climate models, and their effect on the water and energy balance.
  • Developing a new generation of pedotransfer functions that integrate vegetation as surrogate soil structure; revisiting old parameter estimation from PTFs by adding new physical constraints
  • Expanding estimates of global surface evaporation considering soil properties and associated surface resistance


List of publications during the last Working Group Period:

  • Van Looy, K., Bouma, J., Herbst, M., Koestel, J., Minasny, B., Mishra, U., Montzka, C., Nemes, A., Pachepsky, Y., Padarian, J., Schaap, M., Tóth, B., Verhoef, A., Vanderborght, J., van der Ploeg, M., Weihermüller, L., Zacharias, S., Zhang, Y. and Vereecken, H. (2017) Pedotransfer functions in Earth system science: challenges and perspectives. Reviews of Geophysics, 55 (4). pp. 1199-1256. ISSN 1944-9208 doi:
  • Montzka, C., Herbst, M., Weihermüller, L., Verhoef, A. and Vereecken, H.  (2017) A global data set of soil hydraulic properties and sub-grid variability of soil water retention and hydraulic conductivity curves.  Earth System Science Data, 9 (2).   pp. 529-543. doi: 10.5194/essd-9-529-2017.
  • Or, D., and Lehmann, P. (2019). Surface evaporative capacitance: How soil type and rainfall characteristics affect global‐scale surface evaporation. Water Resources Research, 55.
  • Lehmann, P., Merlin, O., Gentine, P., & Or, D. (2018). Soil texture effects on surface resistance to bare‐soil evaporation. Geophysical Research Letters, 45, 10,398–10,405.
  • Rahmati et al. (2018). Development and analysis of the Soil Water Infiltration Global database, Earth Syst. Sci. Data, 10, 1237–1263,
  • Vereecken, H., Weihermüller, L., Assouline, S., Šimůnek, J., Verhoef, A., Herbst, M., et al. (2019). Infiltration from the pedon to global grid scales: An overview and outlook for land surface modeling. Vadose Zone Journal, 18, 180191.

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