A Ph.D. position ! Advanced Soil Biota-Hydraulics Interface for the WHETGEO-GEOSPACE system

Project Overview

This subproject, funded under the ICOSHELL project, aims to develop an integrated modeling
system that explicitly accounts for the dynamic interactions between soil biota activity and soil
hydraulic properties. Building upon the WHETGEO-1D and 2D frameworks, we will implement a
novel coupling between soil fauna population dynamics and plants root growth, evolving soil
hydraulic characteristics. The modelling system implemented will be eventually used for studying
the feedback between soil-vegetation hydrology.

Key Objectives

• Extend the WHETGEO model architecture to incorporate time-varying soil hydraulic properties influenced by soil biota 
• Implement the Kosugi soil water retention curve model with parameters that dynamically evolve based on biological activity
• Develop and integrate a population dynamics module for key soil engineers (earthworms, ants, termites)
• Create a comprehensive validation framework using laboratory and field experimental
• data

Figure from Enrico Chiesa Master Thesis

Methodological Approach

The core innovation of this subproject is the implementation of a feedback loop between
 biological activity and soil physics. Following Meurer et al. (2020), we will start to model how earthworm populations modify soil structure, but significantly expand this approach by:

• Replacing the van Genuchten model with the Kosugi water retention curve formulation, which provides a more direct physical interpretation of pore size distribution
• Developing a differential equation system where the Kosugi parameters (median pore size and standard deviation) are directly modified by biological activity
• Implementing these dynamics within the robust NCZ algorithm of WHETGEO, ensuring numerical stability across diverse conditions
• The population dynamics will be modeled as a set of ordinary differential equations representing different functional groups of soil engineers, their reproduction, mortality, and activity rates as functions of environmental conditions (temperature, moisture, organic matter)

Expected Outcomes

This integration will allow to better capture:

• The temporal evolution of soil infiltration capacity following land-use changes

• The self-reinforcing positive feedback loops of ecosystem restoration, where initial

vegetation changes trigger soil biological activity that further enhances water retention

• The resilience of soil hydrological function under climate change scenarios

Implementation Timeline

Months 1-6: Preliminary studies, doctoral school activities

Months: 6-18 Implement Kosugi model in WHETGEO framework, develop and integrate

population dynamics module Months 18-24: Validate against experimental data Months 32-36:

Upscale to field applications and integration to estimate catchment scale effects. Study effects of

soil management

Possible collaborations

EPFL Lausannne, Prof. Sara Bonetti and Dr. Concetta D'Amato

Info: abouthydrology <at>  gmail.com