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T. A. Abiye and K. C. Leketa
1 Introduction
Groundwater, often considered a strategic resource in Africa, is not well understood, despite its role in addressing clean water shortage for the vast population.
Compounding this, groundwater is under pressure from uncontrolled waste disposal,
mining effluents, excessive pumping for irrigation and industrial activities (Abiye
et al. 2011; Abiye 2013a, b, 2015). Groundwater plays a vital role, predominantly in
arid and semi-arid regions, fulfilling an increasing water demand due to its resilience
to short-term climatic variation. In arid and semi-arid regions, aquifers receive limited
recharge from sporadic rainfall (Selaolo 1998; Abiye 2016). Therefore, it is necessary
to dedicate attention to sustainable development policy in the region. In the Limpopo
River Basin, groundwater exploitation is unregulated and in most cases storage and
recharge history are unknown. The basin hosts about 18 million inhabitants within
the 408,250 km
2 catchment, including portions of Botswana, South Africa, Mozambique and Zimbabwe, with a total average rainfall ranging from 300 to 1050 mm/yr
across the catchment (Owen 2011).
The potential impact of climate change on groundwater has been researched
in depth globally, with a dominant interest in arid and semi-arid regions due to
the scarcity of surface water. High evaporation due to an increase in temperature
(IPCC 2018) and low rainfall obviously have a tremendous impact on surface water
availability. Constant improvement in the modeling of global climatic variables also
contributes to understanding the extent of climate change at different levels, even
though the capacity to utilize data at the local level is very limited.
In order to investigate the isotopic characteristics of groundwater that is in great
demand by local communities and the industrial sector, different sites with a known
groundwater history in the Limpopo River Basin have been considered in this study
(Fig. 1).
Groundwater recharge originates from rainfall with a buffer zone that serves as
ambient impoundment, which either directly or indirectly replenishes aquifers that
later release water onto the surface through wells, springs and base flow. Therefore, it
is essential to understand the status of climate at the time of rainfall event and subsequent recharge into the aquifer. Naturally, groundwater recharge is a slow process
that can be subjected to extreme climatic variation. Particularly in semi-arid and arid
regions, rainfall occurs in an unpredictable manner, which restricts regular aquifer
recharge. Hence, people rely on the available groundwater without knowing the
recharge history that is necessary for knowledge-based groundwater management.
It is known that an increasing global ambient temperature leads to a change
in precipitation and atmospheric moisture, which ultimately affects the amount of
recharge to aquifers (Négrel and Petelet-Giraud 2011). Groundwater provides an
archive of past climate variations by recording changes in the recharge amount or
the chemical and isotopic evolutionary history of a groundwater system (Hughes
et al. 2011). Négrel and Petelet-Giraud (2011) investigated the recharge conditions
and groundwater characteristics of big aquifers in Europe at a large scale, involving
recent, Holocene and Pleistocene components and their eventual mixing. If isotopic
T. A. Abiye and K. C. Leketa
1 Introduction
Groundwater, often considered a strategic resource in Africa, is not well understood, despite its role in addressing clean water shortage for the vast population.
Compounding this, groundwater is under pressure from uncontrolled waste disposal,
mining effluents, excessive pumping for irrigation and industrial activities (Abiye
et al. 2011; Abiye 2013a, b, 2015). Groundwater plays a vital role, predominantly in
arid and semi-arid regions, fulfilling an increasing water demand due to its resilience
to short-term climatic variation. In arid and semi-arid regions, aquifers receive limited
recharge from sporadic rainfall (Selaolo 1998; Abiye 2016). Therefore, it is necessary
to dedicate attention to sustainable development policy in the region. In the Limpopo
River Basin, groundwater exploitation is unregulated and in most cases storage and
recharge history are unknown. The basin hosts about 18 million inhabitants within
the 408,250 km
2 catchment, including portions of Botswana, South Africa, Mozambique and Zimbabwe, with a total average rainfall ranging from 300 to 1050 mm/yr
across the catchment (Owen 2011).
The potential impact of climate change on groundwater has been researched
in depth globally, with a dominant interest in arid and semi-arid regions due to
the scarcity of surface water. High evaporation due to an increase in temperature
(IPCC 2018) and low rainfall obviously have a tremendous impact on surface water
availability. Constant improvement in the modeling of global climatic variables also
contributes to understanding the extent of climate change at different levels, even
though the capacity to utilize data at the local level is very limited.
In order to investigate the isotopic characteristics of groundwater that is in great
demand by local communities and the industrial sector, different sites with a known
groundwater history in the Limpopo River Basin have been considered in this study
(Fig. 1).
Groundwater recharge originates from rainfall with a buffer zone that serves as
ambient impoundment, which either directly or indirectly replenishes aquifers that
later release water onto the surface through wells, springs and base flow. Therefore, it
is essential to understand the status of climate at the time of rainfall event and subsequent recharge into the aquifer. Naturally, groundwater recharge is a slow process
that can be subjected to extreme climatic variation. Particularly in semi-arid and arid
regions, rainfall occurs in an unpredictable manner, which restricts regular aquifer
recharge. Hence, people rely on the available groundwater without knowing the
recharge history that is necessary for knowledge-based groundwater management.
It is known that an increasing global ambient temperature leads to a change
in precipitation and atmospheric moisture, which ultimately affects the amount of
recharge to aquifers (Négrel and Petelet-Giraud 2011). Groundwater provides an
archive of past climate variations by recording changes in the recharge amount or
the chemical and isotopic evolutionary history of a groundwater system (Hughes
et al. 2011). Négrel and Petelet-Giraud (2011) investigated the recharge conditions
and groundwater characteristics of big aquifers in Europe at a large scale, involving
recent, Holocene and Pleistocene components and their eventual mixing. If isotopic