the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Modelling of water and energy exchanges over a sparse olive orchard in semi-arid areas
Wafa Chebbi
Vincent Rivalland
Pascal Fanise
Aaron Boone
Lionel Jarlan
Hechmi Chehab
Zohra Lili Chabaane
Valérie Le Dantec
Gilles Boulet
Abstract. In the Mediterranean basin, olive orchards occupy a large fraction of agricultural lands due to its sustainability to harsh conditions, drought in particular. Since most modeling tools to simulate vegetation functioning are not meant to represent very sparse crops (i.e., rainfed olive trees have a vegetation fraction cover ranging from 2 to 15 %), computing the water needs and the vulnerability to drought of an olive orchard is a challenge. There is indeed a very high contribution of the bare soil signal to the total fluxes, and it is difficult to decipher the contribution of the tree from that of the entire surface. In this context, in an attempt to study the olive tree hydrological functioning at field scale (38 ha), an experimental site was setup and a Soil–Vegetation–Atmosphere (SVAT) model has been applied. To represent the orchard soil–plant–atmosphere interactions, a simulation with default settings was assessed using parameters derived from both the literature and ground measurements. In this default configuration, neither the predicted actual nor the potential transpiration could reach the observed transpiration acquired during the wet season (R2 = 0.67, the Root Mean Square Error (RMSE) = 5.63 mm week−1). We show that the model fails to reproduce the relevant leaf surface that transpires. To address this issue and to improve the estimate of the year-to-year variability of the olive tree transpiration, we propose guidance on how a SVAT model can be modified to more appropriately represent the hydrological functioning of a sparse orchard. Once the tree transpiration is accurately simulated (R2 = 0.93, RMSE = 1.62 mm week−1), we evaluated whether the fully coupled (single patch) or a fully uncoupled (two patch) system better reproduced the total fluxes and their components. Owing to the independent characteristics of the soil columns inherent in the assumption of the 2-patch version, the bare soil column shows a deficiency if the topsoil root extraction is not accounted for. We deduced that we cannot accurately reproduce the soil evaporation in this configuration. This study open perspectives for a better representation of water fluxes over sparse tree crops into both hydrological and SVAT models.
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Preprint
(2187 KB)
Wafa Chebbi et al.
Interactive discussion


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RC1: 'Review of the manuscript HESS-2020-104', Anonymous Referee #1, 04 May 2020
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AC1: 'reply to RC1: 'Review of the manuscript HESS-2020-104', Anonymous Referee #1, 04 May 202', wafa chebbi, 25 May 2020
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AC1: 'reply to RC1: 'Review of the manuscript HESS-2020-104', Anonymous Referee #1, 04 May 202', wafa chebbi, 25 May 2020
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RC2: 'Review', Anonymous Referee #2, 16 Jun 2020
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AC2: 'author response to the reviewer 2 comments', wafa chebbi, 14 Jul 2020
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AC2: 'author response to the reviewer 2 comments', wafa chebbi, 14 Jul 2020
Interactive discussion


-
RC1: 'Review of the manuscript HESS-2020-104', Anonymous Referee #1, 04 May 2020
-
AC1: 'reply to RC1: 'Review of the manuscript HESS-2020-104', Anonymous Referee #1, 04 May 202', wafa chebbi, 25 May 2020
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AC1: 'reply to RC1: 'Review of the manuscript HESS-2020-104', Anonymous Referee #1, 04 May 202', wafa chebbi, 25 May 2020
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RC2: 'Review', Anonymous Referee #2, 16 Jun 2020
-
AC2: 'author response to the reviewer 2 comments', wafa chebbi, 14 Jul 2020
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AC2: 'author response to the reviewer 2 comments', wafa chebbi, 14 Jul 2020
Wafa Chebbi et al.
Wafa Chebbi et al.
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