|
This project was started in 1994 by the Directorate: Geohydrology (Dr. Milo Simonic)
to ascertain the influence of rainfall on the groundwater quality and to determine
the time series and spatial trends in the groundwater quality on the national scale.
Currently 369 monitoring points are being sampled twice a year, that is before and
after rainfall season (October and April). The sampling itself is undertaken in
most of the provinces of South Africa by qualified personnel of the Department of
Water Affairs (DWA).
During the monitoring Geosite (borehole/spring) selection process as much information
as possible was gathered, which was later stored in the National Groundwater Database
(Open-NGDB). These Geosites are also registered on the Water Management System (WMS),
referred to as ZQM-Stations.
Routine sampling usually covers macro-elements. The samples are analysed by
the Directorate: Resource Quality Studies (RQS) at DWAF’s Roodeplaat Dam laboratory.
The chemical analyses are captured on the WMS.
Due to the well-established National/Regional infrastructure of the monitoring programme,
several other hydro-chemical constituents are covered from time to time, i.e.
Trace Elements (metallic determinants in groundwater), Environmental Isotopes (Stable and Radiogenic) and Radioactivity (gross alpha/beta and chemical uranium content).
External laboratories are also contracted to perform special analyses, i.e.
- Council For Scientific and Industrial Research (CSIR):
- Quaternary Laboratory (stable isotope in rainwater and radio-carbon in groundwater)
- Atmospheric Laboratory (Low level Chemistry in rainwater)
- Nuclear Energy Corporation of South Africa (Necsa):
- Radio Analysis Nuclear Services (radioactivity in groundwater)
- iThemba LABS Johannesburg (all radiogenic isotopes, stable isotopes and radio-carbon
in groundwater).
Results will be used as a supporting tool to determine the changes in time / space
in ambient water quality in South Africa.
In addition, this data is required to update the Groundwater Resource Assessment
(GRA II) data sets. A geostatistical assessment
of the groundwater quality data was performed in 2002, from where some changes in
the monitoring programme was recommended. A second, and probably a more comprehensive
geostatistical assessment, will be performed in 2008 to establish the future operational
programme for the NGwQMP.
One special off-shoot from this monitor programme, which has now been completed
in two time slots (1999 - 2000 and 2007 - 2008), is the hydro-chemistry sampling/analysis
of the National Dolomitic Eyes of South Africa. This sampling exercise is performed
under contract with the CSIR-Pretoria and covers above-mentioned analytical package,
as well as CFC’s (chloro-fluro-carbon) from selected eyes. Chloro-Fluro-Carbons
have been suggested as a replacement for the now “outdated” 3Hydrogen
(Tritium) tracer for groundwater flow assessments.
Data from the NGwQMP is currently available on the DWA’s WMS system and subsequently
the environmental isotope data will be uploaded to the WMS as well.
It is, however, recommended that when WMS data is to be used for groundwater investigation,
the Directorate: Hydrological Service, Groundwater Resource Assessment & Monitoring
(GRAM) office is notified accordingly. This is due to the fact that some of
the samples have been sampled under different conditions, which may have caused
a variation in the hydro-chemical character of the groundwater samples.
For any further information please contact
Dr. Eddie van Wyk.
|