Root Water Uptake Models
A text below was copied from Simunek et al. (2024).
The spatiotemporal pattern of root water uptake (RWU) depends on multiple factors, including soil moisture availability and plant root biomass distribution. The non-uniformity of soil moisture and its impact on RWU is often mitigated by various coexisting processes, such as compensated root water uptake (CRWU) and hydraulic redistribution (HR). Compensated root water uptake represents the ability of plants to preferentially extract water from the wet zone to offset a reduction in RWU from the water-stressed zone (e.g., Jarvis, 1989; Šimůnek and Hopmans, 2009). On the other hand, hydraulic redistribution refers to the passive transfer of soil moisture through the root system from a relatively wet soil zone to drier soil layers under reduced transpiration demand.
Root water uptake in most or all previous HYDRUS versions is described using the macroscopic approach of Feddes et al. (1978). The approach is now generalized in HYDRUS such that the model can simulate root water and solute uptake, account for the effects of both water and salinity stress on root water uptake, and additionally consider possible active and passive root contaminant or nutrient uptake (Šimůnek and Hopmans, 2009). Root water and solute uptake processes can be treated as being non-compensated or compensated (Jarvis, 1989), while users can select the degree of compensation (Šimůnek and Hopmans, 2009). Environmental stresses and compensation in this approach are considered purely empirical, with the model unable to simulate additional processes such as hydraulic lift.
To overcome the limitation of HYDRUS not being able to consider these processes and to demonstrate the importance of simultaneously considering CRWU and HR in estimating daily transpiration and RWU distributions under nonuniform soil moisture conditions, Thomas et al. (2023) implemented multiple mechanistic root water uptake models, including those of de Jong van Lier et al. (2006, 2008, 2009, 2013), Couvreur et al. (2012, 2014ab), and Nimah and Hanks (1973ab), in addition to the existing models of Jarvis (1989) and Feddes et al. (1978). The applications demonstrated much flexibility to account for the various processes involved. Implementing the models into the HYDRUS platform to simultaneously consider CRWU and HR and making them available to HYDRUS users should improve the accuracy of RWU predictions, and it will undoubtedly facilitate and encourage future research in this area.
- Project Group: Root Water Uptake Model
- Description: Examples demonstrating the use of various (both empirical and physically-based) root water uptake models.
- Availability: Download HYDRUS projects now (3.2 MB)
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Project
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Dim
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Description
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1D-Test1-C
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1D
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1D Test: Couvreur model.
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1D-Test1-F1
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1D
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1D Test: Feddes model, uncompensated.
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1D-Test1-F2
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1D
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1D Test: Feddes model, compensated.
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1D-Test1-H1
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1D
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1D Test: Nimah and Hanks model with hydraulic lift.
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1D-Test1-H2
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1D
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1D Test: Nimah and Hanks model without hydraulic lift.
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1D-Test1-L
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1D
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1D Test: de Jong van Lier model.
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1D-Test2-C
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1D
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Water flow in a field soil profile under grass, Couvreur model.
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1D-Test2-F
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1D
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Water flow in a field soil profile under grass, Feddes model.
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1D-Test2-H1
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1D
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Water flow in a field soil profile under grass, Nimah and Hanks model without hydraulic lift.
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1D-Test2-H2
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1D
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Water flow in a field soil profile under grass, Nimah and Hanks model with hydraulic lift.
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1D-Test2-L
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1D
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Water flow in a field soil profile under grass, de Jong van Lier model.
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2D-Test1-C
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2D
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2D Test: Couvreur model.
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2D-Test1-F1
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2D
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2D Test: Feddes model, uncompensated.
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2D-Test1-F2
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2D
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2D Test: Feddes model, compensated.
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2D-Test2-C
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2D
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Two-Dimensional RWU Problem: Couvreur model.
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2D-Test1-F
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2D
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Two-Dimensional RWU Problem: Feddes model.
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3D-Test2-C
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3D
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Three-Dimensional RWU Problem: Couvreur model.
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3D-Test1-F
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3D
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Three-Dimensional RWU Problem: Feddes model.
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References
- Šimůnek, J., G. Brunetti, D. Jacques, M. Th. van Genuchten, and M. Šejna, Recent developments and applications of the HYDRUS computer software packages since 2016, Vadose Zone Journal, 23(1), e20310, 29 p., doi: 10.1002/vzj2.20310, 2024. (Supplementary Material)
- Thomas, A., B. K. Yadav, J. Šimůnek, Water uptake by plants under heterogeneous soil moisture conditions: A comprehensive numerical and experimental analysis, Agricultural Water Management, 292, 108668, 13 p., doi: 10.1016/j.agwat.2024.108668, 2024. (Supplementary Material)