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222 Bond, Van Wyk proposed the following primary characteristics for four types of groundwater. Group A: Highly mineraRzed chloride waters lal Waters usually contain >3500 mg r' TDS (Bond, 1946: 1 000 - 4 000 mg r'l. Ibl There is a high chloride content, which is generally >30% of TDS. (cl Soda alkalinity (Na2C03 or NaHC0 3 1 is never present. (d) High salinity water is confined to the Cretaceous beds along the Natal North Coast, with most boreholes abandoned due to the high salinity. Group B: Mineralized chloride waters lal TDS values range from 750 - 2 500 mg r', although there is little difference in percentage composition between Group A and B waters. Ibl Waters have a relatively high chloride content averaging 40% of TDS. Van Wyk 119631 maintained that the high salinity of the groundwaters is due to wind-borne salts derived from the Indian Ocean·. Icl There is some difference in the composition of waters from the Stormberg lava and Karoo sediments. Main differences include: (il The pH of water in the Karoo sediments averages 8,1 which is greater than in the basalt 17,11. (iil The soda alkalinity (Na2C03 or NaHC0 3 ) of water from the Karoo sediments is very low, while in the basalt, alkalinity averages >9%, up to 50% of TDS. • For a further discussion see Murgatroyd, A.L., 1983. Spatial variations in precipitation chemistry over Natal, South Africa, South African Journal of Science. VOL 79(101, p. 408 - 410.
223 111DJ11ll1li (d) Waters of Group B are found in the fairly flat and bush-clad Lowveld areas, extending far inland along the flats and up the main river valleys. Group C: Slightly saline waters (a) TDS values are usually less than 600 mg r', although there is little difference in percentage composition between Group C, and Group A and B waters. (b)· Group C waters are evident in three different localities, namely the coastal zone, the Lebombo Mountains, and along the escarpment separating the Lowveld and Middleveld. (c) In the coastal zone most of the Group C waters (found in Tertiary and Recent sands) overlie Group A waters present in the Cretaceous beds. Accordingly, in the False Bay area (St Lucia) where the sand is thin, all shallow boreholes and wells have Group C waters, while deep boreholes which penetrate the underlying Cretaceous beds, yield Group A waters. Further south however, in the vicinity of KwaMbonambi and Mposa the sand is more than 60 m deep and rests directly on granite and Karoo rocks. No highly mineralized waters are found even in deeper boreholes (at depths exceeding 90 m), which penetrate the underlying Cretaceous rocks. Waters of the higher reaches of the Lebombo Mountains where springs are plentiful, have a low percentage of (sea-derived) salts due to continual leaching. The leachate is discharged from the lower-lying springs and little concentration of salts can occur. By contrast, Group B waters are found in rhyolite in the flat, low lying areas in the vicinity of Hluhluwe station and Ingweni (where springs are absent no leaching takes place). Van Wyk (1963) maintained that a similar process of leaching by springs also operates along the escarpment stretching from Eshowe through Melmoth, Mahlabatini, and Nongoma to Magudu in the north, with a low percentage of salts apparent. Group D: Temporary hard (carbonate) waters (a) TDS values average 276 mg £"' (Bond, 1946: generally < 150 mg £"1)- equivalent to Bond's Group E.
- Page 178 and 179: 174 Bate, 1992}*. The use of water
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222<br />
Bond, Van Wyk proposed the following primary characteristics for four types <strong>of</strong><br />
groundwater.<br />
Group A: Highly mineraRzed chloride waters<br />
lal Waters usually contain >3500 mg r' TDS (Bond, 1946: 1 000 - 4 000 mg r'l.<br />
Ibl There is a high chloride content, which is generally >30% <strong>of</strong> TDS.<br />
(cl Soda alkalinity (Na2C03 or NaHC0 3 1 is never present.<br />
(d) High salinity water is confined to the Cretaceous beds along the Natal North Coast,<br />
with most boreholes abandoned due to the high salinity.<br />
Group B: Mineralized chloride waters<br />
lal TDS values range from 750 - 2 500 mg r', although there is little difference in<br />
percentage composition between Group A and B waters.<br />
Ibl Waters have a relatively high chloride content averaging 40% <strong>of</strong> TDS. Van Wyk<br />
119631 maintained that the high salinity <strong>of</strong> the groundwaters is due to wind-borne<br />
salts derived from the Indian Ocean·.<br />
Icl There is some difference in the composition <strong>of</strong> waters from the Stormberg lava and<br />
Karoo sediments. Main differences include:<br />
(il The pH <strong>of</strong> water in the Karoo sediments averages 8,1 which is greater than<br />
in the basalt 17,11.<br />
(iil The soda alkalinity (Na2C03 or NaHC0 3 ) <strong>of</strong> water from the Karoo sediments<br />
is very low, while in the basalt, alkalinity averages >9%, up to 50% <strong>of</strong><br />
TDS.<br />
• For a further discussion see Murgatroyd, A.L., 1983. Spatial variations in precipitation chemistry over<br />
Natal, South Africa, South African Journal <strong>of</strong> Science. VOL 79(101, p. 408 - 410.
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