| Abstract |
Study area: Upper Zambezi Catchment, Southern Africa
Study focus: Climate change influence on groundwater is still poorly understood especially in
developing countries with a limited monitoring network. In this study, groundwater-climate interactions
are investigated for the Kalahari Aquifer, an alluvial aquifer system. Three datasets
were used that include Standard Precipitation Evapotranspiration Index (SPEI) data from 1920 to
2022, GRACE groundwater storage anomaly (GWA) data from 2009 to 2022 and climate mode
(ENSO, Atlantic Multi-decadal Oscillation (AMO) and Pacific decadal oscillation (PDO) from 1950
to 2022.
New hydrological insights for the region: Using SPEI, it was found that severe droughts (SPEI < 2)
occurred in 1991/92, 1994/95, 1997/98, 2001/02, 2004/05, 2011/12, 2015/16, 2018/19 likely
impacting groundwater storage. SPEI aggregated to 3 months (SPEI-3) correlated with GRACE
groundwater storage annomaly (GWA) data with an R2 of ~0.5. This was indicative of short-term
response to effects of droughts. Nino 3.4 (ENSO) and AMO affect groundwater in time scales of
inter-annual (4–8 years) and inter-decadal (32–64 years) repeat cycles. Spatially, based on geographysical
weighted regression (GWR), SPEI-3 showed strong correlation (R2 = 0.6–0.9) predominately
on the western regions of the Kalahari Aquifer, whereas, the southern portions has a
low R2 (< 0.4) likely controlled by aquifer structure and water table dynamics hence spatial
heterogenity. Adaptation to climate influence on groundwater will require intervention that
balance management and technical interventions. |
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