Validation of a spatial-temporal soil water movement and plant water uptake model

Research Team: James Heppell
Investigators: Tiina Roose, Sevil Payvandi

Water movement through the soil and up through the plant.

We present a generalization of the model by Roose and Fowler (2004a) for water uptake by a plant root system from soil. The model provides an estimate of the water saturation level within the soil at different depths, and the uptake of water by the root system. We use the data in Smethurst et al (2012) to validate our model and obtain a fully calibrated system for plant water uptake. We use linear and non-linear fitting techniques to fit the model to the soil water profile data by searching for the optimal combination of plant and soil parameters.

The stochastic nature of the algorithms used, enforces repeats in the optimisation process, which can be run in parallel. Due to the size of the problem and the rich data available (hourly data for 10 years) the use of the supercomputer at Southampton University (Iridis 3) is necessary for the convergence of the Kriging algorithm.

When compared quantitatively to other models such as CROPWAT, our model achieves a better fit to the experimental data because of the simpler, first, second and third order terms present in the boundary condition, as opposed to complicated non-linear functions. In addition, our model estimates the water saturation level at different depths in the soil rather than an average over the entire depth and therefore has the potential to more accurately model the plant water uptake and enables us to link this model to a plant nutrient uptake one, at a later stage.

Roose, T. and Fowler, A. (2004a) A model for water uptake by plant roots. Journal of theoretical biology, 288, 155-171.

Smethurst, J., Clarke, D. and Powrie, W. (2012) Factors controlling the seasonal variation in soil water content and pore water pressures within a lightly vegetated clay slope. Geotechnique, 62, (5), 429-446.

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Computational Modelling Group

Validation of a spatial-temporal soil water movement and plant water uptake model

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