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ISMC News 16 Nov.

TERENO + GEWEX-ISMC: SoilWat + Featured Soil Modeller + Vacancies


Terrestrial Environmental Observatories

The recent newsletter of the German TERENO observatories includes articles on

  • 10 years TERENO-SoilCan
  • Data on the flood catastrophe
  • Helmholtz research programme 2021-2027  "Changing Earth - Sustaining our Future"
  • OZCAR-TERENO Conference 2021
  • and many more...

Editorial: The consequences of global warming
Since 2018, Germany has experienced multiple periods of drought. In July of this year, we saw devastating flooding. The recently published first part of the Intergovernmental Panel on Climate Change’s (IPCC) new assessment report makes clear that more frequent weather extremes, such as heat waves, droughts or heavy rain, are the result of global warming. And there is more to come. The IPCC warns that without immediate countermeasures, our atmosphere could experience a temperature increase of 1.5 degrees Celsius already in the next 20 years.

Policymakers must decide on which concrete measures should be taken in response. The next UN climate conference in November 2021 in Glasgow will map out the path ahead. In the meantime, our job as scientists is to continue gathering data and facts, and developing forecasts. At TERENO we are currently engaged with colleagues across Europe to evaluate data on the droughts and flooding, since all of these extreme weather events happened in areas where we have measurement instruments installed. This highlights the importance of gathering long-term data for being able to classify such weather extremes. It also confirms that the sites were chosen well for recording the regional consequences of climate change.

Along with evaluating data, we also seek dialogue with fellow researchers, as well as opportunities to learn from each other and develop joint projects. Certainly a terrific opportunity for this is the first joint conference hosted by TERENO and OZCAR, the French Critical Zone research network. Despite the pandemic, we hope the hybrid format, with its mix of virtual and in-person attendance, will bring together as many researchers as possible and provide plenty of stimuli for scientific exchange and future cooperations.

Happy reading.
Harry Vereecken
TERENO Coordinator

Link TERENO Newsletter


Featured Soil Modeller

Sustainable groundwater management  through modeling groundwater-surface water dynamics

Salini Sasidharan is an emerging young scientist in the critical areas of Environmental Science and Engineering, including groundwater quantity and quality management, sustainable irrigated agriculture, and resilient urban and rural water resources infrastructures. She received a B.Sc. in Biotechnology degree (2008) from Mahatma Gandhi University, India, and an M.Sc. in Biotechnology degree (2010) from the University of East London (UEL), United Kingdom. Then, Salini worked as a Microbiology Research Assistant from June 2010 to June 2012 at UEL. In 2012, she received the International Ph.D. Scholarship from National Center for Groundwater Research and Training. She completed her Ph.D. in 2016 from Flinders University in collaboration with CSIRO, Australia. Her Ph.D. research focused on fate, transport, and retention of viruses, bacteria, and nanoparticles in saturated porous media. Since 2017 she has been working as a Postdoctoral Scientist at the University of California, Riverside, and USDA ARS Salinity Lab, USA. Her postdoctoral research focuses on investigating the performance of various engineering techniques such as drywells, infiltration basins, and Ag-MAR for enhanced managed aquifer recharge (MAR). Dr. Sasidharan established the use of fundamental soil physics and hydrology on water flow, contaminant fate and transport, subsurface soil hydraulic properties, stochastic heterogeneity, 1D, and (2D/3D) numerical modeling to solve large spatial and temporal scale problems such as groundwater quantity and quality. As evidence of her excellent research record and impact, she will be appointed as a Sustainable Groundwater Management Engineer (Assistant Professor from Jan 2022) at Oregon State University, USA, a legislatively funded position to develop an internationally recognized research program on groundwater-surface water dynamics, fate, and transport of materials in groundwater, socio-hydrology, incorporating variability and uncertainty in decision making around groundwater management, and the response to systems under changing environmental and regulatory conditions.



Please tell us briefly about yourself and your research interest.

Climate change projections with extreme heatwaves, severe droughts, and an increase in precipitation significantly impact sustainable agriculture and urban resilience. Groundwater is a critical water supply resource, and unstainable pumping has led to groundwater depletion, land subsidence, and compromised groundwater quality. My research focuses on various challenges of MAR, including water quantity, water quality, clogging, engineering designs of the infrastructure, numerical modeling, site selection, and regulatory standards for sustainable groundwater management. My research was the first to evaluate the performance of a vadose zone infiltration system called drywell and advocated its use as a potential MAR technique. My research demonstrated the role of site-specific subsurface heterogeneity on infiltration & recharge rate and arrival time & location of recharged water, and how numerical modeling tools can be applied to determine the ideal location for MAR and groundwater monitoring well 1 & 2. In another study, I compared drywell and infiltration basin (IB) and demonstrated that five drywells could infiltrate and recharge more water than 70 m diameter IB 3. My field-scale drywell work at an Army Basin in CA helped mitigate the local flooding issue, recharge the groundwater table, and support the Army's Net Zero Program, a comprehensive strategy for sustainable energy, water, and solid waste management 1 & 4. Regulatory and policy concerns over microbial pathogen migration from subsurface to groundwater challenge MAR. I have conducted extensive research to understand the virus transport process under stochastic subsurface heterogeneity to determine the best-case and worst-case scenarios for virus removal 5 & 6.


How did you first become interested in soil modelling and learn about ISMC?

As a biotechnology graduate, I was unfamiliar with soil science or soil modeling during my B.Sc. and M.Sc degrees. My Master's thesis was on microbial source tracking on Thursley Nature Reserve, in Surrey, UK. In this project, I have investigated the potential sources of contaminants such as nutrients and microbes causing an algal bloom in a lake in the nature reserve, which led to the habitat destruction and decline in the population of several dragonflies native to this reserve. I have only used microbiology, molecular biology, and bioinformatics tools to investigate the problem in my dissertation. However, during this research, I realized that to understand how the contaminants were transported from the source to the lake and come up with practical solutions, I needed to understand the transport process in soil. This motivated me to pursue a Ph.D. in Environmental Science and Engineering and conduct fundamental research to understand the factors controlling colloids' retention, release, and transport in saturated porous media. During my Ph.D. I understood that microbial transport is also a big concern during MAR.  Currently, the virus liquid phase inactivation is considered as the only removal process during transport in MAR. I have conducted extensive column experiments and inverse modeling to understand the influence of pore-scale variations in water velocity, solution and solid-phase chemistry, temperature, grain size, virus size, shape, and type, nano- and micro-scale roughness, and nanoscale chemical heterogeneity on continuum-scale virus retention and release parameters 7-15. My research was the first to determine blocking in virus transport and established a two-site kinetic model to optimize blocking, irreversible and reversible attachment, and solid-phase inactivation. I then used a combination of lab-scale column experiments using site-specific soil samples, inverse optimization of virus removal parameters, and HYDRUS (2D/3D) numerical modeling to predict virus transport from MAR. I learned about the ISMC, when I was invited to join the Early Career Researcher Hydrology Group 2019 workshop at AGU. I was involved in writing a review paper by engaging with young scientists in soil hydrology and modeling under the guidance of senior scientists from across the world. I was a runner-up candidate for the 2019 ISMC Executive Board elections and recently joined as an early career member of the Soil Model Intercomparison Science Executive Board. I have been actively involved with this community to establish a collaborative network with soil science and modeling scientists worldwide and exchange knowledge and exciting news from the soil modeling world.


Can you share with us your current research focus? And, please tell us briefly how your research could contribute to ISMC Science Panel's activities

Groundwater is a critical water supply resource, and unstainable pumping has led to groundwater depletion, land subsidence, and compromised groundwater quality. The Sustainable Groundwater Management Act (SGMA) was formed to protect groundwater resources.  Recently, I have proposed the use of drywell as a MAR technique in agricultural fields in Central Valley, California, in conjunction with Ag-MAR operations to enhance the recharge and minimize contaminant mobility from the Ag-MAR field. This research idea has been well received and was funded by USDA-NIFA (0.5M USD). This work attracted other Groundwater Sustainability Agencies and farmers across the Central Valley to achieve the goals outlined by SGMA. I will characterize the soil hydraulic property of the project site using a combination of lab- and field-scale analysis coupled with modeling tools. This study will validate the role of site-specific subsurface heterogeneity on infiltration & recharge rate and arrival time & location of recharged water, and how numerical modeling tools can be applied to determine the ideal location for MAR and groundwater monitoring well. In addition, surface clogging and in-situ clay mobilization reduce the lifespan of MAR. In this project, I will develop a pre-treatment unit to remove various contaminants from source water. These modeling activities can be relevant to the broad ISMC Science Panel's activities as they provide improved modeling tools to predict the water flow and contaminant transport across vast temporal and spatial scales in the context of managed aquifer recharge and groundwater management.


Please tell us how can ISMC help you advance in your career?

ISMC's aims to bring together leading modeling experts within all major soil disciplines and address key scientific gaps by leading international conferences/workshops and connecting soil scientists through various working groups of critical soil problems. Attending the ISMC Soil Hydrology Workshop and being an Executive Board member opened an excellent opportunity to enhance my network with great soil modeling scientists worldwide. In addition, such an opportunity significantly boosted my visibility in the soil and hydrology research area. I believe that continuing this engagement in many ways and allowing me to contribute to the ISMC activities and mission will be an excellent arena to place a signature of my soil and hydrology research and grow as a successful woman scientist.  


What resources or skills would you recommend that early career members of ISMC should acquire? And how can ISMC help and support early career members in this regard?

Research and development activities for technological advancements are essential for sustainable economic growth and wellbeing in many societies. Therefore, early career researcher should not narrow their research interest. On the contrary, it is crucial to have a bigger vision and develop our research field to provide a positive economic and technological impact globally. Therefore, I think an early career researcher should not be afraid to leave the comfort zone, explore multidisciplinary approaches, and learn and use new tools, instruments, or techniques to utilize your full potential. At the same time, one needs to realize that we are not the expert of every scientific tool and technique and, therefore, should be open to collaboration and expanding network with other experts, scientists, and industry partners to achieve your overall mission. The early career scientist should also place a great effort on developing successful stakeholder relationships with various state, local, and federal agencies, industry partners, and the public who are the potential beneficiaries of your research. ISMC can be a great hub for offering collaborative and networking opportunities for young scientists by coordinating various workshops, conferences, and seminars. ISMC could also host Webinars with invited early career speakers and provide a spotlight for them to be exposed to an international soil research community. Many new modeling tools available in the markets are often costly for early career members to buy for their research. Similarly, many modeling courses are also costly to attend. Therefore, coordinating workshops to introduce various modeling products/software would help us get exposure to the newly available modern modeling tools and make a more informed decision on using such models in our research.


  1. Sasidharan, S., Bradford, S.A., Šimůnek, J., DeJong, B., and Kraemer, S.R., 2018. Evaluating drywells for stormwater management and enhanced aquifer recharge. Advances in Water Resources, 116, pp.167-177. Impact Factor: 3.673 DOI
  2. Sasidharan, S., S. A. Bradford, J. Šimůnek, and S. R. Kraemer. 2019. Drywell infiltration and hydraulic properties in heterogeneous soil profiles. Journal of Hydrology, Impact Factor: 3.727 DOI
  3. Sasidharan, S., S. A. Bradford, J. Šimůnek, and S. R. Kraemer. 2020. Comparison of Simulated Recharge from Drywells and Infiltration Basins. Journal of Hydrology. Impact Factor: 3.727 DOI
  4. Sasidharan, S., S. A. Bradford, J. Šimůnek, and S. R. Kraemer. 2020. Groundwater Recharge from Drywells Under Constant Head Conditions. Journal of Hydrology. p.124569. Impact Factor: 3.727 DOI
  5. Sasidharan, S., S.A. Bradford, J. Šimůnek, S.R. Kraemer. Virus transport from drywells under constant head conditions: A modeling study, Water Research. Impact Factor: 9.130 DOI
  6. Torkzaban, S., Hocking, M., Bradford, S.A., Tazehkand, S.S., Sasidharan, S., and Šimůnek, J., 2019. Modeling Virus Transport and Removal during Storage and Recovery in Heterogeneous Aquifers, Journal of Hydrology. Impact Factor: 3.727 DOI
  7. S. A. Bradford, S. Sasidharan, H. Kim, A. Gomez-Flores, T. Li, C. Shen. Colloid Interaction Energies for Surfaces with Steric Effects and Incompressible and/or Compressible Roughness. Langmuir: the ACS Journal of Surfaces and Colloids. Impact Factor: 3.833
  8. Sasidharan, S., S.A. Bradford, J. Šimůnek, and S. Torkzaban. 2018. Minimizing virus transport in porous media by optimizing solid-phase inactivation, Journal of Environmental Quality. Impact Factor: 2.652 DOI
  9. Bradford, S. A., Sasidharan, S., Kim, H., and Hwang, G., 2018. Comparison of types and amounts of nanoscale heterogeneity on bacteria retention. Frontiers in Environmental Science. DOI
  10. Sasidharan, S., S.A. Bradford, J. Šimůnek, S. Torkzaban, and J. Vanderzalm. 2017. Transport and fate of viruses in sediment and stormwater from a Managed Aquifer Recharge site. Journal of Hydrology 555: 724-735, Impact Factor: 3.727 DOI
  11. Sasidharan, S., S.A. Bradford, S. Torkzaban, X. Ye, J. Vanderzalm, X. Du, and D. Page. 2017. Unraveling the complexities of the velocity dependency of E. coli retention and release parameters in saturated porous media. Science of The Total Environment 603–604: 406-415, Impact Factor: 4.900 DOI
  12. Bradford, S.A., H. Kim, C. Shen, S. Sasidharan and J. Shang. 2017. Contributions of Nanoscale Roughness to Anomalous Colloid Retention and Stability Behavior. Langmuir: the ACS Journal of Surfaces and Colloids 33: 10094-10105, Impact Factor: 3.833 DOI
  13. Sasidharan, S., S. Torkzaban, S.A. Bradford, P.G. Cook, and V.V. Gupta. 2017. Temperature dependency of virus and nanoparticle transport and retention in saturated porous media. Journal of Contaminant Hydrology 196: 10-20. Impact Factor: 2.547 DOI
  14. Sasidharan, S., S. Torkzaban, S.A. Bradford, R. Kookana, D. Page, and P.G. Cook. 2016. Transport and retention of bacteria and viruses in biochar-amended sand. Science of The Total Environment 548–549: 100-109, Impact Factor: 4.900 DOI
  15. Sasidharan, S., S. Torkzaban, S.A. Bradford, P.J. Dillon, and P.G. Cook. 2014. Coupled effects of hydrodynamic and solution chemistry on long-term nanoparticle transport and deposition in saturated porous media. Colloids and Surfaces a-Physicochemical and Engineering Aspects 457: 169-179, Impact Factor: 2.714 DOI


GEWEX-ISMC SoilWat Initiative

SoilWat seeks to enhance the representation of soil processes in climate models (Zeng et al. 2021), and currently focuses on: soil properties and parameters, soil physical processes (e.g., infiltration, surface evaporation, water and heat flow), soil-root hydraulics, soil-groundwater dynamics, and soil-water/energy/carbon cycles.

  • For soil properties and parameters, it is evident that using different Pedotransfer Functions (PTFs) will lead to a considerable range of uncertainties in land surface fluxes (Weihermüller et al. 2021). SoilWat is therefore calling for the harmonization of soil hydro-thermal properties and their PTFs as used in land surface models, which will facilitate understanding uncertainties originating from different model structures and physics. Within SoilWat, the Soil Parameter Model intercomparison Project (SP-MP) aims to assess the influence of soil parameters on the diverse behaviour of LSM (Gudmundsson and Cuntz 2016).
  • Soil physical processes are highly impacted by soil structural effects, which modify the long-term hydrologic partitioning between relatively slow deep percolation and fast surface runoff (Vereecken et al. 2019; Fatichi et al. 2020). Structure-corrected soil hydraulic properties can be developed via establishing a functional relationship between vegetation information (as surrogates of soil structure) and soil hydraulic properties (Bonetti, Wei, and Or 2021).
  • Soil-root hydraulics play an important role in controlling stomatal conductance and transpiration (Vanderborght et al. 2021). A working group is putting efforts in benchmarking functional-structural root architecture models to evaluate how certain representations of root architecture and model approximations influence simulated root water uptake (Schnepf et al. 2020).
  • Considering soil-groundwater dynamics in LSMs to enable investigations of the water cycle ‘from bedrock to atmosphere’ is still very challenging. It requires a multiscale hydrogeological model (providing hydrologic parameters for groundwater modelling), groundwater observation platform, and groundwater flow model to capture 3D flow in the subsurface at multiple scales and resolutions (Condon et al. 2021).
  • Via coupling a soil model with a vegetation model and a radiative transfer model, one will be able to link soil processes to remotely sensed canopy level photosynthesis and solar-induced fluorescence (SIF) (Wang et al. 2021), at the regional to global scale. With the rapid development of SIF remote sensing and datasets, it would be worthwhile to consider a Soil-SIF WG for studying the soil-water/energy/carbon cycles.

Bonetti, Sara, Zhongwang Wei, and Dani Or. 2021. “A Framework for Quantifying Hydrologic Effects of Soil Structure across Scales.” Communications Earth & Environment 2021 2:1 2 (1): 1–10.

Condon, L.E., S. Kollet, M.F.P. Bierkens, G.E. Fogg, R.M. Maxwell, M.C. Hill, A. Verhoef, A.F. Van Loon, M. Sulis, and C. Hendricks Fransen, H.J. Abesser. 2021. “Global Groundwater Modeling and Monitoring: Opportunities and Challenges.” Water Resources Research, in press.

Fatichi, Simone, Dani Or, Robert Walko, Harry Vereecken, Michael H. Young, Teamrat A. Ghezzehei, Tomislav Hengl, Stefan Kollet, Nurit Agam, and Roni Avissar. 2020. “Soil Structure Is an Important Omission in Earth System Models.” Nature Communications 11 (1): 1–11.

Gudmundsson, Lukas and Matthias Cuntz. 2016. “Soil Parameter Model Intercomparison Project (SP-MIP): Assessing the Influence of Soil Parameters on the Variability of Land Surface Models.” GEWEX-ISMC SoilWat workshop, Leipzig.

Schnepf, Andrea, Christopher K. Black, Valentin Couvreur, Benjamin M. Delory, Claude Doussan, Axelle Koch, Timo Koch, et al. 2020. “Call for Participation: Collaborative Benchmarking of Functional-Structural Root Architecture Models. The Case of Root Water Uptake.” Frontiers in Plant Science 0 (March): 316.

Vanderborght, Jan, Valentin Couvreur, Felicien Meunier, Andrea Schnepf, Harry Vereecken, Martin Bouda, and Mathieu Javaux. 2021. “From Hydraulic Root Architecture Models to Macroscopic Representations of Root Hydraulics in Soil Water Flow and Land Surface Models.” Hydrology and Earth System Sciences Discussions, 1–37.

Vereecken, Harry, Lutz Weihermüller, Shmuel Assouline, Jirka Šimůnek, Anne Verhoef, Michael Herbst, Nicole Archer, et al. 2019. “Infiltration from the Pedon to Global Grid Scales: An Overview and Outlook for Land Surface Modeling.” Vadose Zone Journal 18 (1): 1–53.

Wang, Yunfei, Yijian Zeng, Lianyu Yu, Peiqi Yang, Christiaan Van Der Tol, Qiang Yu, Xiaoliang Lü, Huanjie Cai, and Zhongbo Su. 2021. “Integrated Modeling of Canopy Photosynthesis, Fluorescence, and the Transfer of Energy, Mass, and Momentum in the Soil-Plant-Atmosphere Continuum (STEMMUS-SCOPE v1.0.0).” Geoscientific Model Development 14 (3): 1379–1407.

Weihermüller, Lutz, Peter Lehmann, Michael Herbst, Mehdi Rahmati, Anne Verhoef, Dani Or, Diederick Jacques, and Harry Vereecken. 2021. “Choice of Pedotransfer Functions Matters When Simulating Soil Water Balance Fluxes.” Journal of Advances in Modeling Earth Systems 13 (3): e2020MS002404.

Zeng, Yijian, Anne Verhoef, Dani Or, Matthias Cuntz, Lukas Gudmundsson, Lutz Weihermueller, Stefan Kollet, Jan Vanderborght, and Harry Vereecken. 2021. “GEWEX-ISMC SoilWat Project: Taking Stock and Looking Ahead.” GEWEX Newsletter 2:



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