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Estimating water fluxes in the critical zone using water stable isotope approaches in the Groundnut and Ferlo basins of Senegal
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  • Djim M.L. Diongue,
  • Christine Stumpp,
  • Olivier Roupsard,
  • Didier Orange,
  • Frederic C. Do,
  • Serigne Faye
Djim M.L. Diongue
Universite Cheikh Anta Diop de Dakar

Corresponding Author:[email protected]

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Christine Stumpp
Universitat fur Bodenkultur Wien Department Wasser-Atmosphare-Umwelt
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Olivier Roupsard
Institut de recherche pour le developpement Senegal
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Didier Orange
Institut de recherche pour le developpement Senegal
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Frederic C. Do
Institut de recherche pour le developpement Senegal
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Serigne Faye
Universite Cheikh Anta Diop de Dakar
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Sustainable water management in semi-arid agriculture practices requires quantitative knowledge of water fluxes within the soil-vegetation-atmosphere system. Therefore, we used stable-isotope approaches to evaluate evaporation (Ea), transpiration (Ta), and groundwater recharge (R) at sites in Senegal's Groundnut basin and Ferlo Valley pasture region during the pre-monsoon, monsoon, and post-monsoon seasons of 2021. The approaches were based upon (i) the isothermal evaporation model (for quantifying Ea); (ii) water and isotope mass balances (to partition Ea and Tfor groundnut and pasture); and (iii) the piston displacement method (for estimating R). Ea losses derived from the isothermal evaporation model corresponded primarily to Stage II evaporation, and ranged from 0.02–0.09 mm d-1 in the Groundnut basin, versus 0.02–0.11 mm d-1 in Ferlo. At the groundnut site, Ea rates ranged from 0.01 to 0.69 mm d-1; Ta was in the range 0.55–2.29 mm d-1; and the Ta/ETa ratio was 74–90%. At the pasture site, the ranges were 0.02–0.39 mm d-1 for Ea; 0.9–1.69 mm d-1 for Ta; and 62–90 % for Ta/ETa.  The ETa value derived for the groundnut site via the isotope approach was similar to those from eddy covariance measurements, and also to the results from a previous validated HYDRUS-1D model. However, the HYDRUS-1D model gave a lower Ta/ETa ratio (23.2%). The computed groundwater recharge for the groundnut site amounted to less than 2% of the local annual precipitation. Recommendations are made regarding protocols for preventing changes to isotopic compositions of water in samples that are collected in remote arid regions, but must be analysed days later. The article ends with suggestions for studies to follow up on evidence that local aquifers are being recharged via preferential pathways
21 Jul 2022Submitted to Hydrological Processes
22 Jul 2022Submission Checks Completed
22 Jul 2022Assigned to Editor
22 Jul 2022Reviewer(s) Assigned
27 Sep 2022Review(s) Completed, Editorial Evaluation Pending
29 Sep 2022Editorial Decision: Revise Major
08 Nov 20221st Revision Received
11 Nov 2022Submission Checks Completed
11 Nov 2022Assigned to Editor
11 Nov 2022Reviewer(s) Assigned
14 Nov 2022Reviewer(s) Assigned
09 Dec 2022Review(s) Completed, Editorial Evaluation Pending
13 Dec 2022Editorial Decision: Accept
Jan 2023Published in Hydrological Processes volume 37 issue 1. 10.1002/hyp.14787