EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Groundwater storage in the Horn of Africa drylands dominated by seasonal rainfall extremes

Markus Adloff1,2, Michael Bliss Singer3,4,5, David McLeod1, Katerina Michaelides1,5,6, Nooshin Mehrnegar3, Eleanor Hansford1,7, Chris Funk8, and Dann Mitchell1,6
Markus Adloff et al.
  • 1School of Geographical Sciences, University of Bristol, Bristol, United Kingdom (
  • 2now: School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
  • 3School of Earth and Ocean Sciences, Cardiff University, Cardiff, United Kingdom
  • 4Water Research Institute, Cardiff University, Cardiff, United Kingdom
  • 5Earth Research Institute, University of California Santa Barbara, Santa Barbara, USA
  • 6Cabot Institute for the Environment, University of Bristol, Bristol, United Kingdom
  • 7now: European Centre for Medium-Range Weather Forecasts (ECMWF), Reading, United Kingdom
  • 8UC Santa Barbara Climate Hazards Center, Santa Barbara, USA

Rural communities in the Horn of Africa Drylands (HAD) rely on the availability of soil moisture for crop growth and groundwater for drinking water supply for people and livestock. Recent negative trends in March-May rainfall (‘long rains’) have decreased soil moisture with negative consequences for the livelihoods in HAD communities, who have become increasingly vulnerable to multi-season droughts affecting crops and livestock. These increasingly common failed ‘long rains’, propagate into agricultural drought, causing famines, and lead to major humanitarian intervention across HAD. However, the links between seasonal rainfall (‘long rains’ and ‘short rains’ in October-December) and regional groundwater storage in HAD have not been explored. We examined trends in seasonal rainfall from various gridded datasets alongside an analysis of total water storage (TWS) from GRACE satellite data. Multiple rainfall datasets corroborate declining ‘long rains’ and increasing ‘short rains’, and a 3-hr (MSWEP) dataset reveals the disproportionate contribution of extreme rainfall to totals within both seasons. We also found that TWS generally increased across the HAD region between 2002 and 2017, and that the GRACE TWS signal is primarily composed of groundwater storage changes for this region, rather than trends in soil moisture. We then found that groundwater storage variability correlates strongly with seasonal rainfall on interannual and decadal scales, and it is particularly correlated with extreme rainfall in both rainy seasons. We highlight the importance of increasingly large Indian Ocean Dipole events in dominating extreme rainfall and correspondingly high TWS and groundwater recharge within the October-December rainy season. While groundwater recharge in HAD by high-intensity rainfall is generally high for the March-May rainy season, it is increasing for the ‘short rains’ season. These findings raise the possibility that increasing groundwater availability across HAD could be exploited to offset the ‘long rains’ decline, potentially mitigating their climate change impacts on soil moisture, crops, and drinking water supplies.

How to cite: Adloff, M., Singer, M. B., McLeod, D., Michaelides, K., Mehrnegar, N., Hansford, E., Funk, C., and Mitchell, D.: Groundwater storage in the Horn of Africa drylands dominated by seasonal rainfall extremes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15470,, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.