The study describes the application complimentary geohydrologic tools to investigate the
geohydrological properties of an alluvial channel aquifer and its interaction with the river surface
water resources. Primary field investigations were designed to determine the geologic, hydraulic,
hydrogeochemical and solute transport properties of the alluvial channel aquifer as an important
component of the groundwaterâsurface water (GWâSW) interaction system. The secondary
investigations were then aimed at assessing groundwater discharge and recharge mechanisms of the
alluvial channel aquifer at a local scale (< 1000 m). A water balance model was developed for the
groundwaterâsurface system as a tertiary level of investigation.
Geological characterisation results show the spatial variation in the physical properties of
unconsolidated aquifer materials between boreholes and at different depth. The drawdown
derivative diagnostic analysis shows that the alluvial channel aquifer system response during
pumping can be described by the following major groundwater flow characteristics; Typical Theis
response; transition period from initial Theis response to radial acting flow (RAF); radial acting flow
in the gravelâsand layer and river single impermeable boundary effects. Detailed studies of the
hydrogeochemical processes in the alluvial aquifer system have shown that dissolution of silicate
weathering, dolomite and calcite minerals, and ion exchanges are the dominant hydrogeochemical
processes that controls groundwater quality. Quantitative and qualitative investigations indicate
that the alluvial channel aquifer is being recharged through preferential infiltration recharge as
facilitated by cavities and holes created by the burrowing animals and dense tree rooting system.
Tracer tests under natural gradient were successfully conducted in an alluvial channel aquifer, thus
providing some advice on how to conduct tracer breakthrough tests under natural gradients in a
typical alluvial channel aquifer.
The findings of the study also highlights the value of developing a water balance model as a
preliminary requirement before detailed GWâSW interaction investigations can be conducted. Based
on the theoretical conceptualizations and field evidence it is suggested that studies be conducted to
determine if alluvial channel aquifers can be further classified based on the nature of the hosting
river channel. The classification would split the alluvial channel aquifer into alluvial cover and
fracturedâbedrock, or a combination of the two. The applications of the PhD thesis findings are not
only limited to the case study site, but have important implications for GWâSW interaction studies,
groundwater resource development and protection in areas where groundwater occurs in alluvial
channel deposits.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-05272013-111554 |
| Date | 27 May 2013 |
| Creators | Gomo, Modreck |
| Contributors | Prof GJ van Tonder |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-05272013-111554/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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