Catchment-scale Richards equation-based modeling of evapotranspiration via boundary condition switching and root water uptake schemes.

Camporese, Matteo; Daly, Edoardo et Paniconi, Claudio (2015). Catchment-scale Richards equation-based modeling of evapotranspiration via boundary condition switching and root water uptake schemes. Water Resources Research , vol. 51 , nº 7. pp. 5756-5771. DOI: 10.1002/2015WR017139.

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Résumé

In arid and semiarid climate catchments, where annual evapotranspiration (ET) and rainfall are typically comparable, modeling ET is important for proper assessment of water availability and sustainable land use management. The aim of the present study is to assess different parsimonious schemes for representing ET in a process-based model of coupled surface and subsurface flow. A simplified method for computing ET based on a switching procedure for the boundary conditions of the Richards equation at the soil surface is compared to a sink term approach that includes root water uptake, root distribution, root water compensation, and water and oxygen stress. The study site for the analysis is a small pasture catchment in southeastern Australia. A comprehensive sensitivity analysis carried out on the parameters of the sink term shows that the maximum root depth is the dominant control on catchment-scale ET and streamflow. Comparison with the boundary condition switching method demonstrates that this simpler scheme (only one parameter) can successfully reproduce ET when the vegetation root depth is shallow (not exceeding approximately 50 cm). For deeper rooting systems, the switching scheme fails to match the ET fluxes and is affected by numerical artifacts, generating physically unrealistic soil moisture dynamics. It is further shown that when transpiration is the dominant contribution to ET, the inclusion of oxygen stress and root water compensation in the model can have a considerable effect on the estimation of both ET and streamflow; this is mostly due to the water fluxes associated with the riparian zone. Key Points: Simple, parsimonious ET schemes for integrated hydrological models are assessed Boundary condition switching is suitable only for shallow root depths Oxygen stress and root water compensation influence riparian zone ET dynamics.

Type de document:	Article
Mots-clés libres:	catchment scale; evapotranspiration; modeling; Richards equation; root water uptake
Centre:	Centre Eau Terre Environnement
Date de dépôt:	19 avr. 2018 18:52
Dernière modification:	27 nov. 2019 15:15
URI:	https://espace.inrs.ca/id/eprint/3815

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