Sebbar B. E., Simonneaux Vincent, Khabba S., Chehbouni Abdelghani, Merlin O. (2026). Assessing the groundwater recharge of a steep-sided catchment from thermal-derived evapotranspiration estimates : usefulness of methods for correcting topographical effects. Journal of Hydrology, 664 (B), 134457 [17 p.]. ISSN 0022-1694.
Titre du document
Assessing the groundwater recharge of a steep-sided catchment from thermal-derived evapotranspiration estimates : usefulness of methods for correcting topographical effects
Evapotranspiration (ET), a key component of the hydrological cycle, is commonly derived on a global scale from thermal-infrared remote sensing data. Thermal-derived ET estimates can hence be used to assess the water budget of land surfaces. However, significant uncertainties in such ET data can lead to non-closure of the water balance. This is particularly the case in rugged catchments where topography introduces substantial variability in the meteorological forcing of ET models, whose systematic errors propagate through the water balance calculation. This study addresses the limited attention given to topographical effects on thermal-based ET by developing a daily framework for ET mapping that accounts for topography (ET-TOPO+). Its usefulness is evaluated by comparison to two widely used ET products, WaPOR and SSEBop, in estimating groundwater recharge (GWR) in a steep-sided catchment in the High Atlas, Morocco, from 2017 to 2022, using in-situ measurements of streamflow and precipitation. WaPOR and SSEBop do notaccount for topography while ET_TOPO+ corrects for the topography-induced variability in meteorological conditions. Assessment against in-situ measurements at two contrasted sites shows that ET_TOPO+ provides the most accurate monthly ET estimates with higher correlation (an average of 0.81) and minimal bias (a maximum of -5 mm/month). At the annual scale (2017-2022), GWR ranged from -110 to + 42 mm/year (SSEBop), -104 to +27 mm/year (WaPOR), and -86 to +71 mm/year (ET_TOPO+). The inter-annual water balance assessment shows that ET_TOPO+ provides the most realistic GWR considering the morphological and geological context, averaging 1 mm/year over five hydrological years. SSEBop and WaPOR produced values of -58 and -33 mm/year, respectively, showing an overall overestimation of both ET products at watershed scale since negative values are unrealistic in this context. These findings highlight the importance of considering the topographical influence on thermal-derived ET estimates in assessing terrestrial water-cycle dynamics and water resources.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
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Sciences du milieu [021]
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Hydrologie [062]
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Télédétection [126]
