Hydrogeology of the Sterkfontein Cave System, Cradle of Humankind, South Africa

Abstract A water level rise of almost 3 m in the space of two years in the Sterkfontein Cave system since late-2009 necessitated the re-routing of the tourist path through the cave to successively higher elevations on three occasions. It also raised concern for a possible association with copious acidic and sulphate-rich mine water drainage from the West Rand Goldfield (a.k.a. Western Basin) starting in early-2010, and the related threat to the UNESCO-inscribed fossil site. Although these circumstances have had little impact on the tourist value of the site, a prognosis of the impact on cave water level and quality is indicated by virtue of its karst setting and palaeontological significance. Historical and recent potentiometric data, together with ancillary hydrogeological and hydrochemical information acquired in the course of a water resources monitoring programme for the broader Cradle of Humankind World Heritage Site, provides new insight into the hydrogeology of the cave system. An improved understanding of the hydrophysical and hydrochemical response of the cave water system sheds light on the location of this system within the water resources environment. It is proposed that the present-day maximum cave water level is constrained to an elevation of ~1440 m above mean sea level. The recent electrical conductivity of 78 mS/m for cave water is 32% greater than the 59 mS/m recorded in mid-2010 and earlier. Similarly, the recent sulphate concentration of 161 mg/L is 178% greater than the 58 mg/L recorded before 2010. Compared to coeval values for ambient karst groundwater represented by the normative Zwartkrans Spring water, the magnitude of the increases in the springwater are similar, viz. 48% (from 84 to 124 mS/m) in salinity and 166% (from 154 to 409 mg/L) in sulphate. Although a distinct mine water impact is evident in both instances, the values indicate a muted impact on the cave water chemistry compared to the springwater. These and other documented observations better inform the threat from various poorer quality water sources to the fossil site in particular, and to the broader karst water resource in general. This contextualises concern for the hydroenvironmental future of Sterkfontein Cave and other nearby fossil sites such as Swartkrans, Rising Star and Bolt’s Farm. The dynamic response of the water resources environment to a variety of hydrological and hydrogeological drivers reinforces the need for monitoring vigilance across a range of disciplines.

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The impact of acid mine drainage on the ecology of the Cradle of Humankind and Krugersdorp Game Reserve on the West Rand

Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie ◽

10.4102/satnt.v35i1.1367 ◽

2016 ◽

Vol 35 (1) ◽

Author(s):

François Durand

Keyword(s):

Sulphuric Acid ◽

Mine Water ◽

World Heritage Site ◽

Acid Mine Water ◽

The West ◽

Gold Mines ◽

Acid Mine ◽

Game Reserve ◽

Cradle Of Humankind ◽

The Impact

The Witwatersrand Supergroup is the world’s richest goldbearing geological deposit. This approximately 2.8 milliard years old unit is overlain by the 2.71–2.67 milliard years Ventersdorp Supergroup which is in turn overlain by the 2.67–2.46 milliard years Chuniespoort Group of the Transvaal Supergroup. The dolomite-rich Chuniespoort Group also contains a large aquifer which supplies water to farms in southern Gauteng, southeastern North West Province and northern Free State. The megalitres of water in the dolomite flooding the adjacent gold mines in the Witwatersrand Supergroup need to be pumped out constantly to keep the mines operational. The gold mines in the Witwatersrand Supergroup are amongst the deepest mines in the world and those in Gauteng are up to 3 km deep. The mines of the Central Rand, the East Rand and the West Rand, which extend over an area of 100 km, were shut down, one after the other, as the gold ore was depleted to a depth of approximately 3 km and it became uneconomical to continue. The enormous mine void, occupying several million cubic metres, gradually started to fill up with groundwater again, causing the springs in the vicinity of the Witwatersrand mines to flow after more than a century of dewatering. The water flowing from these springs, however, is not clean dolomitic water but acid mine water containing a high concentration of sulphuric acid, sulphate salts and metals, including radioactive heavy metals. The auriferous geological layers constituting the Witwatersrand Supergroup also contain large quantities of iron pyrite (FeS2) which forms sulphuric acid when it comes into contact with water and oxygen. The deterioration of the ecology in the Krugersdorp Game Reserve and the Cradle of Humankind World Heritage Site is a good example of the negative impact acid mine water has on the ecology.

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Impact on operation of the Middle Route Project of South-to-North Water Diversion

MATEC Web of Conferences ◽

10.1051/matecconf/201824601040 ◽

2018 ◽

Vol 246 ◽

pp. 01040

Author(s):

Hui Wan ◽

Huiyong Huang ◽

Sidong Zeng ◽

Yibo Yan ◽

Yongyan Wu ◽

...

Keyword(s):

Water Resources ◽

Water Level ◽

Water Diversion ◽

Safe Operation ◽

Ecological Civilization ◽

Long Distance ◽

Emergency Rescue ◽

North Water ◽

Control Failure ◽

The Impact

The inter-basin water transfer project is one of the most important means to solve the uneven distribution of water resources in time and space, rationally allocate water resources, and promote the construction of water ecological civilization. Research on the operation impact and channel hydraulic response is meaning for the safe operation of long-distance water conveyance canals. Taking the Middle Route Project (MRP) of South-to-North Water Diversion (SNWD) as example, this paper built the onedimensional steady and unsteady flow model and investigated the impact of roughness change, emergency rescue technology and equipment, and sluice control failure. Results showed that increased roughness decreased the water diversion efficiency of MRP to some degree. The emergency rescue technology and equipment occupied the channel section and declined flow capacity. The occurrence of sluice control failure relatively played an increasing impact on upstream water level and a decreasing impact downstream water level and flow discharge. The impact of the above scenarios on the scheduling operation can be reduced to a certain extent by regular cleaning and maintenance, development of rational water emergency rescue project, development of staff skill, etc. This research can provide support for safe operation and regulation of the MRP of SNWD.

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Naledi: An example of how natural phenomena can inspire metaphysical assumptions

HTS Teologiese Studies / Theological Studies ◽

10.4102/hts.v73i3.4507 ◽

2017 ◽

Vol 73 (3) ◽

Author(s):

Francois Durand

Keyword(s):

South Africa ◽

Alternative Explanation ◽

Single Species ◽

Natural Phenomena ◽

Cave System ◽

The World ◽

Fossil Bones ◽

Fossil Site ◽

Cradle Of Humankind ◽

Remote Part

A new fossil site was discovered in the Rising Star Cave in 2013 in the Cradle of Humankind in South Africa. This site which has yielded 1550 hominin bones so far is considered to be one of the richest palaeoanthropological sites in the world. The deposition of the fossils in a remote part of the cave system, approximately 100 m from the entrance, has resulted in a great deal of speculation. The relative inaccessibility of the site and the number of fossil bones it contained and the fact that virtually all these bones were those of a single species of hominid led to the conclusion that the bones were not deposited because of natural sedimentary processes, but that these phenomena were evidence of purposeful disposal or even burial of the dead by hominins. If this assumption is true, it would be the earliest evidence of a metaphysical awareness in humankind. The tenuous evidence on which this hypothesis rests will be discussed and a more plausible alternative explanation where water and gravity were responsible for the deposition of the remains is forwarded.

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Induced micro seismicity due to raising mine water level in former coal mines in the eastern Ruhr area (Germany)

10.5194/egusphere-egu21-13040 ◽

2021 ◽

Author(s):

Martina Rische ◽

Kasper D. Fischer ◽

Felix Allgaier ◽

Wolfgang Friederich

Keyword(s):

Water Level ◽

Mine Water ◽

Induced Seismicity ◽

Water Levels ◽

Water Drainage ◽

Seismicity Rate ◽

Ruhr Area ◽

Water Level Rise ◽

Short Period ◽

Stress Changes

FloodRisk is an interdisciplinary project focusing on the effects of mine water level rise in abandoned coal mine regions in Germany. Such effects are heterogeneous ground uplift, stress changes due to the change in pore pressure and the reactivation of potential faults. One of the most directly measurable effects is certainly the induced micro seismicity. It is known from previous studies that the flooding of old mines can lead to a renewed increase level in induced micro seismicity in these regions. In this study &#160;the relationship between mine water rise, fluid-induced stress changes and induced seismicity in the Haus Aden dewatering area in the eastern Ruhr area (Germany) will be investigated in more detail.&#160; For this purpose, we operate a network of currently 21 short period seismic stations in the region of the former "Bergwerk Ost" colliery, which had the highest seismicity rate in the Ruhr area during active underground coal mining. This network is still to be expanded to cover the entire water drainage area, about 30 Raspberry Shake sensors are waiting for the possibility of installation.&#160; Nevertheless, the existing network registered almost 1000 induced micro seismic events in a magnitude range from -0.7 up to 2.6 MLv. Many of these events are &#160;spatially clustered and some show quite high waveform similarity. This allows relative localisation &#160;and can increase the accuracy of the location. The depth location of the earthquakes, within the limits of localisation accuracy, agrees very well with the distribution of seismicity at the time of active mining. The spatial distribution so far seems to be limited by a large inactive transverse fault in the west. It needs to be clarified what influence this fault has on the propagation of mine water in the &#160;underground. The measured temporal trend of the mine water level, after pumps were shut down in mid-2019, shows a strong correlation with the temporal evolution of the observed micro seismicity. In the first &#160;months after the pumps are switched off, the water levels at the observation points rise only slowly and isolated microseismic events occur again. In November 2019, the rise in water levels doubled and at the same time, the strongest induced event in the measurement period was recorded with a magnitude of 2.6 MLv. In the following months, the seismicity rate ranged from 8 to 34 events above 0.5 MLv per month, some of which were felt. A structural geological 3D subsurface model is developed to help to understand the distribution of induced seismicity and the role of the raising mine water level.

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Combining legacy data with new drone and DGPS mapping to identify the provenance of Plio-Pleistocene fossils from Bolt’s Farm, Cradle of Humankind (South Africa)

PeerJ ◽

10.7717/peerj.6202 ◽

2019 ◽

Vol 7 ◽

pp. e6202 ◽

Cited By ~ 2

Author(s):

Tara R. Edwards ◽

Brian J. Armstrong ◽

Jessie Birkett-Rees ◽

Alexander F. Blackwood ◽

Andy I.R. Herries ◽

...

Keyword(s):

South Africa ◽

South African ◽

World Heritage Site ◽

Heritage Site ◽

Fossil Site ◽

Legacy Data ◽

Cradle Of Humankind ◽

The University ◽

Fossil Data ◽

Future Work

Bolt’s Farm is a Plio-Pleistocene fossil site located within the southwestern corner of the UNESCO Hominid Fossil Sites of South Africa World Heritage Site. The site is a complex of active caves and more than 20 palaeokarst deposits or pits, many of which were exposed through the action of lime mining in the early 20th century. The pits represent heavily eroded cave systems, and as such associating the palaeocave sediments within and between the pits is difficult, especially as little geochronological data exists. These pits and the associated lime miner’s rubble were first explored by palaeoanthropologists in the late 1930s, but as yet no hominin material has been recovered. The first systematic mapping was undertaken by Frank Peabody as part of the University of California Africa Expedition (UCAE) in 1947–1948. A redrawn version of the map was not published until 1991 by Basil Cooke and this has subsequently been used and modified by recent researchers. Renewed work in the 2000s used Cooke’s map to try and relocate the original fossil deposits. However, Peabody’s map does not include all the pits and caves, and thus in some cases this was successful, while in others previously sampled pits were inadvertently given new names. This was compounded by the fact that new fossil bearing deposits were discovered in this new phase, causing confusion in associating the 1940s fossils with the deposits from which they originated; as well as associating them with the recently excavated material. To address this, we have used a Geographic Information System (GIS) to compare Peabody’s original map with subsequently published maps. This highlighted transcription errors between maps, most notably the location of Pit 23, an important palaeontological deposit given the recovery of well-preserved primate crania (Parapapio, Cercopithecoides) and partial skeletons of the extinct felid Dinofelis. We conducted the first drone and Differential Global Positioning System (DGPS) survey of Bolt’s Farm. Using legacy data, high-resolution aerial imagery, accurate DGPS survey and GIS, we relocate the original fossil deposits and propose a definitive and transparent naming strategy for Bolt’s Farm, based on the original UCAE Pit numbers. We provide datum points and a new comprehensive, georectified map to facilitate spatially accurate fossil collection for all future work. Additionally, we have collated recently published faunal data with historic fossil data to evaluate the biochronological potential of the various deposits. This suggests that the palaeocave deposits in different pits formed at different times with the occurrence of Equus in some pits implying ages of <2.3 Ma, whereas more primitive suids (Metridiochoerus) hint at a terminal Pliocene age for other deposits. This study highlights that Bolt’s Farm contains rare South African terminal Pliocene fossil deposits and creates a framework for future studies of the deposits and previously excavated material.

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