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Modelling groundwater evapotranspiration in a shallow aquifer in a semi-arid environment

The use of diurnal or seasonal water table flctuation (WTF) to estimate groundwater evapotranspiration (ETG) at diffrent land uses and climate conditions is increasing applied in ecohydrological studies. In this study, we applied the WTF method for a shallow aquifer in an urbanized area in Senegal over the dry season 2000–2013.To analyze the applicability and validity of the WTF method for this site, and to understand the impact of the parameters used in this method, the unsaturated /saturated system was fist simulated using the HYDRUS 1D model. The drawdown of the water table ranges from 18.1 to 113.2 cm and 10.4 to 101.9 cm for a bare soil and a perennial grass scenario and is highly related to the annual rainfall of the previous rainy season. The results indicate that the mean daily FAO-PM reference evapotranspiration rates for this area ranged from 2 to 4 mmd?1 and that the estimated actual evapotranspiration (ETa) from the HYDRUS 1D model ranged between 0.22 to 1.11 and 0.23 to 1.27 mmd?1 in bare soil and vegetative condition, respectively. ETa and ETG were well correlated for the vegetated scenario. However, the WTF method slightly overestimates ETa flxes in the bare soil scenario. The study shows that the decline of ETa with water table depth can be simulated by an exponential function. The overall results indicate that higher ETa values were observed when the water table is shallow, suggesting that ETa is mainly driven by the water table depth at this site.


Auteur(s) : Ousmane Coly Diouf, Lutz Weihermuller, Mathias Diédhiou, Harry Vereecken, Seynabou Cissé Faye, Serigne Faye Samba Ndao Sylla
Année de publication : 2020
Revue : Journal of Hydrology
Type : Article
Mise en ligne par : DIEDHIOU Mathias