Deep, Semi-fossil Aquifers in Southern Africa: From Occasional Findings Towards an Exploration Strategy Prof. Dr. Thomas Himmelsbach Dr. Ralf Klingbeil Federal Institute for Geosciences and Natural Resources (BGR), Germany Department Groundwater & Soil Sciences Stilleweg 2, 30655 Hannover, Germany Phone +49 (0)511 643-2427, Fax +49 (0)511 643-3661 Email: himmelsbach@bgr.de

Actual Catchment of Cuvelai-Basin Etosha Pan: intra-continental endorheic basin Tectonic subsidence since Cretaceous-Tertiary boundary Increased sedimentation since 6 mio. years Different lake levels can be delineated from ancient shore lines up to 1,100 m asl Older and higher lake levels are questionable Backward erosion truncated Kunene und Cubango from basin (35,000 a) Cubango river feeds today together with Cuito river into Okavango Delta … Etosha Salt Pan as final drainage level

Sedimentary Fans in the Cuvelai-Basin Two prominent sedimentary magafans in Cuvelai-Basin Represent deltaic sedimentation Younger Cubango megafan buried older Kunene fan Kunene megafan lies underneath Cubango megafan Relevance for groundwater exploration [source: Miller et al 2010]

Example for Delta Sedimentation (Areal Picture Okavango) [Source: www.wikipedia.org]

Exploration for Ohangwena II Aquifer in Northern Namibia (Cuvelai-Etosha-Basin, Ohangwena) TEM Fluid Finder Good agreement between geophysical soundings, drill core evaluation, groundwater sampling (fluid finder) and hydrogeological modelling

TEM Profile (E–W) Parallel to Axis of Cuvelai-Basin

Groundwater Structure and Conditions Simplified Sketch pan hydraulic separating layer local perched aquifers in un-saturated zone ? extension, storativity and yield precipitation 450 mm/a high salinity aquifer increasing salinity recharge discharge 180 – 240 m

Recharge Occurs in Angola Satellite images indicate swampy areas during wet season Swampy areas located in Angolan highlands, parallel to tectonic lineaments Topography and geological maps indicate favourable infiltration conditions Pilot study on Niipele-Odila catchment before wet season after wet season

Example Caprivi Strip and Okavango Delta

Climate Effects Combined with Tectonic Tilting and Distortion of Entire Southern African Basement - Recent Dry Areas Chobe Swamps Okavango Delta Recent Magkadigkadi Pan [Source: www.wikipedia.de]

Continuation of East African Rift Zone (EARZ)

Helicopter air borne geophysics (EM) along East Caprivi Graben Structure, upper Kalahari aquifer strong indication of palaeo-channels with fresh groundwater Linyanti Fault [Source: Siemon, Roettger & Pielawa 2005 (BGR)]

X-Section B-B´ Okavango Delta Schematic ! Vertically exaggerated Modified after Meier 2008

Summary Recent findings of deep, freshwater aquifers often erratic Exploration strategy needed, comparable to oil and gas exploration Large intra-continental basins in Africa comprise today still hidden fossil or semi-fossil aquifers Exploration requires: Investigating tectonic and sedimentary evolution, paleo-climate and hydrogeological conditions Deep semi-fossil aquifers represent strategic resource for fast growing population and can contribute to climate change adaptation

TBA hotspots in the SADC region What makes the topic you present a hotspot for TBA research? Regional relevance, basic hydrogeological understanding, similarity of TBAs Looking at the topic you present: What are the most pressing issues in relation to: Regional research and transfer into common knowledge, reaching TB river and aquifer commissions Looking at SADC region and all its known and still unmapped TBAs, what are the most pressing issues which need to be focused on in terms of: Regional coordination of research activities and assistance and knowledge transfer to local TBA institutions

Thank you very much for your attention!

Deep, Semi-fossil Aquifers in Southern Africa: From Occasional Findings Towards an Exploration Strategy Prof. Dr. Thomas Himmelsbach Dr. Ralf Klingbeil Federal Institute for Geosciences and Natural Resources (BGR), Germany Department Groundwater & Soil Sciences Stilleweg 2, 30655 Hannover, Germany Phone +49 (0)511 643-2427, Fax +49 (0)511 643-3661 Email: himmelsbach@bgr.de