Preprints
https://doi.org/10.5194/egusphere-2022-22
https://doi.org/10.5194/egusphere-2022-22
 
28 Mar 2022
28 Mar 2022
Status: this preprint is open for discussion.

Influence of intensive agriculture and geological heterogeneity on the recharge of an arid aquifer system (Saq-Ram, Arabian Peninsula)

Pierre Seraphin, Julio Gonçalvès, Bruno Hamelin, Thomas Stieglitz, and Pierre Deschamps Pierre Seraphin et al.
  • Aix Marseille Université, CNRS, IRD, Coll France, INRAE, CEREGE UM 34, 13545 Aix en Provence, France

Abstract. This study assesses the detailed water budget of the Saq-Ram Aquifer System (520 000 km2) over the 2002–2019 period using satellite-gravity data from the Gravity Recovery And Climate Experiment (GRACE). The three existing GRACE solutions (JPL, CSR, GSFC) were tested for their local compatibility to compute groundwater storage variations in combination with soil moisture datasets (VIC, CLSM, NOAH) available from the Global Land Data Assimilation System (GLDAS) land surface models. Accounting for groundwater pumping (15.7 ± 1.1 mm yr-1), artificial recharge (2.2 ± 0.8 mm yr-1) and natural discharge (0.3 ± 0.06 mm yr-1) uniformly distributed over the Saq-Ram domain, the GRACE-derived water mass balance calculation yields a long-term estimate of the domain-averaged natural recharge of 2.4 ± 1.4 mm yr-1, corresponding to 4.4 ± 2.6 % of the annual average rainfall.

Beyond the global approach proposed here, spatial heterogeneities regarding the groundwater recharge were identified. The first source of heterogeneity is of anthropogenic origin. Within agricultural plots, irrigation excess is great enough to artificially recharge the aquifer (i.e. 167 ± 83 mm yr-1 distributed over irrigated areas). However, on the outskirts of these crop areas subjected only to the natural recharge but still influenced by pumping drawdown, there is a risk of relative disconnection from the infiltration front with the declining water table (i.e. the unsaturated zone thickens faster than percolation flows through it), making effective recharge locally zero. The second source of recharge heterogeneity identified here is natural: Volcanic lava deposits (called Harrats on the Arabian Peninsula) which cover 8 % of the Saq-Ram Aquifer domain but contribute to more than 50 % of the total natural recharge. Hence, in addition to this application on the Arabian Peninsula, this study strongly indicates a major control of geological context on arid aquifer recharge which has been poorly discussed hitherto.

Pierre Seraphin et al.

Status: open (until 24 May 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-22', Anonymous Referee #1, 08 May 2022 reply
  • RC2: 'review for egusphere-2022-22 by Seraphin et al.', Anonymous Referee #2, 10 May 2022 reply

Pierre Seraphin et al.

Pierre Seraphin et al.

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Short summary
This study assesses the detailed water budget of the Saq-Ram Aquifer System using satellite-gravity data. Spatial heterogeneities regarding the groundwater recharge were identified: i) Irrigation excess is great enough to artificially recharge the aquifer; ii) Volcanic lava deposits, which cover 8 % of the domain, contribute to more than 50 % of the total natural recharge. This indicates a major control of geological context on arid aquifer recharge which has been poorly discussed hitherto.