Using stable water isotopes to identify spatial-temporal controls on groundwater recharge in two contrasting East African aquifer systems

Samson Oiro (Corresponding Author), Jean-Christophe Comte, Chris Soulsby, Kristine Walraevens

Research output: Contribution to journalArticle

14 Citations (Scopus)
40 Downloads (Pure)

Abstract

Understanding the spatial-temporal variability in groundwater recharge is an essential prerequisite to sustainable management of aquifers. Spatial analysis of groundwater stable isotopes uncovered predominant controls on groundwater recharge in Nairobi Aquifer System (NAS) and South Coast aquifer (SC), two exemplar East-African aquifers relied upon by 7M people. 368 samples were analysed for stable isotopes and basic physico-chemical parameters. The NAS groundwater isotopes are controlled by precipitation orographic effects and enriched recharge from impounded lakes/wetlands. SC isotopes are correlated with water-table depth influencing evapotranspiration. Global Network of Isotopes in Precipitation-GNIP data revealed groundwater recharge during months of heavy rains in NAS, whilst SC experiences spatiotemporally diffuse recharge. Inferred ‘isoscapes’ show; in NAS, (1) direct, rapid recharge favoured by faults, well-drained soils and ample rainfall in uplands, (2) delayed recharge from impounded-lakes and wetlands in midlands, (3) focussed, event-based recharge in floodplains; in SC, diffuse recharge complicated by significant water-table evapotranspiration processes.
Original languageEnglish
Pages (from-to)862-877
Number of pages16
JournalHydrological Sciences Journal
Volume63
Issue number6
Early online date18 Apr 2018
DOIs
Publication statusPublished - 6 Jun 2018

Keywords

  • Groundwater recharge
  • Stable isotopes
  • Aquifer systems
  • Meteoric water line
  • Evaporation effect

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