Data issues
The Freshwater section of the State-of-the-Environment Report is data
intensive. In general, data were available, but in a format that had
to be manipulated for use. Large information gaps do exist,
particularly in areas that may severely impact future water
resources of the country. For instance, there was little readily
available information on effluent volume and quality at a national
level (for industry, domestic and mining). It would require a
separate research project to compile this information. Additionally,
information on waste from informal settlements is not available,
although it is recognised that these have a large impact on water
resources. There is also little information on other non-point
sources of pollution, because they are difficult to quantify.
Water quality data were available from the Hydrological
Information System Quality Database (HIS QualDB) from DWAF.
The data are received from accredited laboratories throughout the
country and are considered to be accurate (the Institute for Water Quality Studies was not
willing to place a level of confidence on this accuracy).
Inaccuracies may occur due to human error in the sampling
process.
Hydrological data were available from the Hydrological
Information System of DWAF. The data accuracy of the whole
database is not possible to establish, but the data from stations
mentioned in this report were evaluated (see Table 3.8 below). In the
case of some rivers, there were not adequate data to estimate the
freshwater flow into estuaries.
| Table 3.8 Accuracy of hydrological data for specific
stations (information from DWAF, Data Quality) |
| RIVER (STATION) |
% GAPS IN DATA
(DAYS) |
% GAPS IN DATA
(MONTHS) |
ESTIMATED
ACCURACY |
COMMENTS |
| Orange (Vioolsdrif) |
3,4 |
7,3 |
Flow < 0,1 m <30%
Flow > 0,1 m 85% |
Accuracy increases
as flow increases |
| Palmiet |
0,7 |
2,5 |
90% |
|
| Gamtoos (Patensie) |
0,4 |
4,6 |
Data unreliable |
|
| Sundays (Addo Drift East) |
2,4 |
10,3 |
Data unreliable |
|
| Great Fish (Matomelo's
Location) |
14,2 |
- |
1969-1974 80 %
1977-1998 85 % |
1974-1977 station
under construction |
| Great Kei (Area 8, Springs B) |
1,3 |
15,5 |
1990-1992 75 %
1992-1998 85 % |
|
| Mgeni (Inanda Location) |
1,7 |
11,8 |
70 % |
Siltation problem |
| Mgeni (Inanda Mission Res.) |
1,0 |
- |
Data reliable |
|
| Tugela (Mandini) |
11,7 |
11,2 |
1956-1959 reliable
1969-1963
unreliable
1963-1997 reliable |
1987-1990 under
construction.
|
| Crocodile (KNP; Tenbosch) |
4,6 |
8,6 |
- |
Underestimation |
| Crocodile (Kalkheuwel) |
1,3 |
6,1 |
± 85% |
|
| Vaal |
3,1 |
9,23 |
90% |
|
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There is also information about Freshwater Systems and Resources in the following reports:
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Metropolitan reports:
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Affairs and Tourism. All Rights Reserved.
Site maintained by the Directorate Environmental Information and Reporting
Last update: October 1999
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