Origin and chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta, Botswana

Akondi, Rawlings N.; Atekwana, Eliot A.; Molwalefhe, Loago N.

doi:10.1080/02626667.2018.1560447

Cited by 10 publications

(6 citation statements)

References 60 publications

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“…The chemical enrichment in the second aquifer is explained either from leaching of dolomitic basement and/or from in situ biogeochemical processes. A similar disconnection between the river water-shallow groundwater of the Delta and the deep groundwater aquifers below and immediately around the Delta has also been demonstrated based on dissolved inorganic carbon (DIC analysis) (Akondi et al, 2019).…”

Section: Proposed Models For the Formation And Geochemical Evolution ...supporting

confidence: 55%

Highly Contrasted Geochemical Pattern in Sediments of the Okavango Delta, Botswana Driven by Dust Supply, Hydrological Heritage and Biogeochemical Reactions

Jolivet

Dauteuil

Dia

et al. 2023

Geochem Geophys Geosyst

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The Okavango Delta in North Botswana is one of the few active alluvial mega-fans developing in an endorheic setting (Assine & Soares, 2004;McCarthy, 2013) (Figure 1). This fan forms a vast swamp flooded annually by water from the highlands of Angola to the North and it supports an exceptional ecosystem in the middle of the semi-arid Kalahari Desert. Due to their isolation, endorheic ecosystems result from tight coupling between climatic, topographic and geologic settings. Changes in one or several of these controlling factors have dramatic effects on the fragile equilibrium of the ecosystems, especially in semi-arid or arid climate contexts (Yapiyev et al., 2017). In the context of rapid climate change and of a regionally increasing anthropogenic pressure, especially on water resources (Ministry of Mineral, Energy and Water Affairs, Republic of Botswana, 1997), improving our knowledge of the structure and functioning of the sensitive Okavango geo-ecosystem is a fundamental challenge. Among the major threats to the ecosystem of the Delta, a decrease in the amount and quality of the water is probably the most important. In order to evaluate the impact of global change on the ecosystem, it is thus necessary to fully understand the hydrology of the Delta. In that respect, describing the geometry, sedimentological structure and geochemical pattern of the various aquifers is essential to understand the geochemical exchanges between the surface and groundwater, the soil and the biosphere.Many studies have already addressed the sedimentation, the hydrology and the vegetation dynamics of the fan in terms of sediment input or water dynamics. A majority of these studies also deal with the effects of anthropogenic activity such as, water pumping, or those of tectonic activity along the faults bordering the rift (Ellery

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Section: Proposed Models For the Formation And Geochemical Evolution ...supporting

confidence: 55%

Highly Contrasted Geochemical Pattern in Sediments of the Okavango Delta, Botswana Driven by Dust Supply, Hydrological Heritage and Biogeochemical Reactions

Jolivet

Dauteuil

Dia

et al. 2023

Geochem Geophys Geosyst

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“…The δD and δ 18 O of the Okavango River samples plot below the GMWL and the LMWL. In fact, the δD and δ 18 O of the samples plot along the trend of the Okavango Delta Evaporation Line (ODEL), consistent with evaporation river water (Dincer et al, 1979;Atekwana et al, 2016;Akondi et al, 2019;Ramatlapeng et al, 2021). The Okavango River samples from the Panhandle plot at or near the intersection of the ODEL, the GMWL and the LMWL (δ 18 O = -6.5 ‰ and δD = -40 ‰) and are less enriched compared to samples from the lower delta, which plot further from the Panhandle samples along the ODEL (Fig.…”

Section: Spatial Evaporation Of Okavango River Watersupporting

confidence: 52%

“…5). In Figure 5, we also show the global meteoric water line (GMWL; Craig, 1961) and the local meteoric water line (LMWL; Akondi et al, 2019;Ramatlapeng et al, 2021). The δD and δ 18 O of the Okavango River samples plot below the GMWL and the LMWL.…”

Section: Spatial Evaporation Of Okavango River Watermentioning

confidence: 99%

“…In principle, the hot wet season should cause greater evaporative enrichment in the δD and δ 18 O of river water, compared to the cooler dry season. Additionally, given that estimates suggest that one third of the water input into the Okavango Delta is from rainfall (Milzow et al, 2009), we should expect the δD and δ 18 O composition of the river water to be shifted by that of the local rain, which has a much broader range in the δD and δ 18 O (Akondi et al, 2019). Yet we observe mostly enrichment of the δD and δ 18 O of river water during the rainy season (Fig.…”

Section: Temporal Evaporation Of Okavango River Watermentioning

confidence: 99%

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Stable hydrogen and oxygen isotopes reveal aperiodic non-river evaporative solute enrichment in the solute cycling of rivers in arid watersheds

Letshele

Atekwana

Molwalefhe

et al. 2023

Science of The Total Environment

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“…While the Okavango Delta hydrology has been particularly well studied over the last few decades (e.g., McCarthy et al 1991;McCarthy and Ellery 1998;McCarthy 2006;Atekwana et al 2016;Akondi et al 2019), the Kwando and Zambezi rivers, which may also be of importance to the Chobe region, have been less studied so far (Tooth et al this book). By analogy to the previous studies in the region (McCarthy, 2006;Atekwana et al 2016;Akondi et al 2019), the surface waters of the region can be classified as calcium-magnesium-(sodium)-bicarbonate type waters for the major rivers (Okavango, Kwando/ Linyanti, and Zambezi; Fig. 6.9).…”

Section: Landscape Components Of the Chobe Enclavementioning

confidence: 99%

Landscapes and Landforms of the Chobe Enclave, Northern Botswana

Mokatse

Diaz

Shemang

et al. 2022

World Geomorphological Landscapes

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The northern part of the Chobe Enclave (an administrative district of northern Botswana) is an agricultural area situated between relatively pristine national parks situated in the Middle Kalahari Basin. It belongs to the Linyanti-Chobe structural basin and constitutes a syntectonic depocenter formed within a large structural depression, known as the Okavango Graben, a tectonic structure of a likely trans-tensional nature. The landscape includes fossil landforms, such as sand dunes, pans, sand ridges, and carbonate islands resulting from palaeo-environmental and palaeo-drainage changes through the Quaternary and associated to (neo)tectonic processes. In addition to riverand wind-reworked Kalahari sands, the sediments include diatomites and carbonate deposits, forming inverted reliefs and originating from palustrine palaeo-environments. The Linyanti-Chobe basin is at the convergence of several ecoregions from tropical and subtropical grasslands to savannas and shrubland biomes. The hydrological cycle in the northern Chobe Enclave is governed by a complex interplay between the Okavango, Kwando, and Upper Zambezi drainage basins, which originate from tropical watersheds of the Angolan highlands. Finally, the widespread development of termite mounds impacts the diversity of soils and sediments of the northern Chobe Enclave, which is also reflected in the vegetation.

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Origin and chemical and isotopic evolution of dissolved inorganic carbon (DIC) in groundwater of the Okavango Delta, Botswana

Cited by 10 publications

References 60 publications

Highly Contrasted Geochemical Pattern in Sediments of the Okavango Delta, Botswana Driven by Dust Supply, Hydrological Heritage and Biogeochemical Reactions

Highly Contrasted Geochemical Pattern in Sediments of the Okavango Delta, Botswana Driven by Dust Supply, Hydrological Heritage and Biogeochemical Reactions

Stable hydrogen and oxygen isotopes reveal aperiodic non-river evaporative solute enrichment in the solute cycling of rivers in arid watersheds

Landscapes and Landforms of the Chobe Enclave, Northern Botswana

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