Surveys
Groundwater
Hydrocensus and data review
Additional boreholes and monitoring
Hydrocensus and data review
After initial data collation and synthesis, including compilation of a project
database, a hydrocensus will be designed and conducted throughout the Berg River
Catchment, with particular focus in the 50 km downstream of the proposed
Skuifraam Dam. This will entail visiting farms, collecting basic groundwater
information (borehole position, depth, yield, abstraction etc.) and measuring
water levels and electrical conductivity. Other organisations such as state
departments, regional and local authorities, farmers unions, drillers and pump
contractors will be contacted to ensure as many of the existing boreholes in the
area are identified. Potential for inclusion into a regional monitoring network
will also be assessed. All data will then be captured onto the project database.
Data thus collated and collected will be analysed and a conceptual
geohydrological model of the catchment developed (Initialisation report). This
will include the construction of groundwater flow direction maps and water
quality maps. Using both surface and groundwater data, an attempt will be made
to assess the surface - groundwater interaction and groundwater-ecosystem
dependence and groundwater contribution to baseflow, and to identify stretches
along the river that may be losing water to the groundwater system. This report
will form the basis for the design of the groundwater monitoring programme.
Additional boreholes and monitoring
Based on the outcome of the first two tasks, a groundwater monitoring network in
the Berg River Catchment will be designed. This network is to link with that
established in the Langebaan Road Aquifer.
As soon as practically possible, water level and water chemistry monitoring of
existing boreholes will be initiated. It is expected quarterly monitoring on
existing boreholes will commence on completion of the hydrocensus, in order to
collect as much information as possible during the project.
Data collection:
· Monitoring will include the measurement of groundwater levels and EC, pH and
temperature in the field and collection of groundwater samples for analysis by
the IWQS in Pretoria. Sampling and the storage and transportation of samples
will be in accordance with recommended sampling procedures (Weaver, 1993).
Monitoring frequency:
· Selected existing boreholes will be monitored on a monthly basis for the
duration of a year. Thereafter, quarterly monitoring will continue until the
completion of the project. On completion of the project this function is to
become the responsibility of the DWAF Regional Office.
In places where existing boreholes cannot be used, dedicated monitoring
boreholes will have to be drilled. Dedicated monitoring boreholes may also be
required to investigate specific issues such as surface - groundwater
interaction or suspected contamination. Proposed drilling sites will be selected
in consultation with DWAF's regional geohydrological staff. It is specifically
required that lithological characteristics be considered in the site selection
process. The consultants will manage the drilling and logging of the estimated
10 boreholes.
It has been requested by the DWAF Regional Office that the 10 additional
boreholes be fitted with continuous data loggers to monitor groundwater levels
and electrical conductivity. This equipment is relatively costly (water levels
only = R 11 700; water level and electrical conductivity = R 35 000), but could
provide very meaningful data regarding surface - groundwater interaction. It is
therefore proposed that 8 water level loggers be installed together with 2 water
level and electrical conductivity loggers. Data will be downloaded from the
loggers every three months to coincide with the baseline monitoring run of
existing boreholes. At the same time, data from continuous rain gauges (to be
supplied and installed by DWAF) will also be downloaded.
Deliverables:
All data collected during the project will be used to compile the Baseline
Report. This report will present:
· a conceptual understanding of groundwater conditions in the catchment,
· an assessment of surface groundwater interaction
· an initial assessment of potential impacts resulting from the construction of
the proposed dam
· the results of monitoring, and
· recommendations for further monitoring.
It is proposed the report will contain sufficient data on which to base an
intermediate-level Reserve determination. Collected data will be submitted to
DWAF electronically for capture onto the NGDB.
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