Establishing geobotanical-geophysical correlations in the north-eastern parts of South Africa for improving efficient borehole siting in difficult terrain

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Date
2007-11
Authors
Meulenbeld, Paul Martin Peter Bernard
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University of the Free State
Abstract
English: The determination whether certain botanic species can be associated and linked to the existence of groundwater resources by considering the relationship of these species with certain lithologies has been studied in the present research with the aid of geophysics, geology, soil quality analysis (geochemistry), aerial photographs and proven borehole records. Ordinary scientific groundwater exploration makes use of methods such as aerial photographic interpretation, geological modelling of the area under investigation by making use of published geological maps and field reconnaissance work, geohydrological concerns and geophysical data interpretation. The scientific approach can further be enhanced by incorporating other scientific fields such as botany and soil science. Any botanical species is a living organism that requires nutrients to function and live. Nutrients are derived from the soil wherein it grows, while soil is a weathering component of the original underlying rock. Differences in soil can be attributed to changes in the composition or type of the natural rock. By including soil and botany in groundwater exploration, the chances of success are increased. Numerous case studies are presented to illustrate that certain botanical species prefer to grow in nutritious places derived from weathered rock, where this rock acts as a groundwater resource. Soil samples taken from these places indicate different soil quality compositions when compared to the surrounding common veld. This phenomenon is representative throughout the entire study, representing various geological formations. The presence of alien rock formations in a fairly homogenous geological environment is indicated by means of geophysical profiles and soundings. Existing boreholes, whether at or removed from geobotanical communities, indicate the importance of such communities since they hint to the keen observer the likely presence of groundwater at such a community. The current study presents aquifer yields obtained at geobotanical communities and the average yield of aquifers in the same geological environment, where most boreholes are drilled without the incorporation of geobotanical indicators. Lastly, the value of soil quality samples is discussed with a preference for CEC-values to indicate geobotanical communities and/or the presence of groundwater. The statistical treatment of the data indicates distinctively that statistically significant regressions exist between geology, geophysics and groundwater as the explanatory variables and CEC and geobotany as the dependent variables.
Afrikaans: Met behulp van geofisika, geologie, grondkwaliteit-analise (geochemie), lugfoto’s en bewese boorgatresultate is bepaal dat sekere botaniese spesies geassosieer en verbind kan word aan die bestaan van grondwaterhulpbronne deur die spesie se verhouding met sekere sedimentêre en andere gesteentes. Gewone wetenskaplike grondwatereksplorasie maak gebruik van metodes soos lugfoto-interpretasie, geologiese modellering van die ondersoekgebied deur gebruik te maak van gepubliseerde geologiese kaarte en verkenningswerk in die veld, geohidrologiese oorwegings en geofisiese data interpretasie. Die wetenskaplike benadering kan verder bevorder word deur ander wetenskaplike velde te inkorporeer soos plantkunde en grondkunde. Enige plantkundige spesie is ‘n lewende organisme wat voedingstowwe benodig om te funksioneer en te lewe. Voedingstowwe word verkry vanaf die grond waarin dit groei. Grond is ‘n verweringskomponent van die oorspronklike onderliggende gesteentes. Verskille in grond kan toegeskryf word aan veranderinge in die samestelling of soort van die oorspronklike gesteente. Deur grond en plantkunde in te sluit in grondwatereksplorasie, word die kanse om sukses te behaal verhoog. ‘n Aantal gevallestudies word aangebied om aan te dui dat sekere botaniese spesies ‘n geneigdheid het om in voedsame plekke te groei, waar die voedingstowwe vanaf verweerde gesteentes kom. Die verweerde gesteente dien as ‘n grondwaterhulpbron. Grondmonsters wat geneem is van hierdie lokaliteite dui op verskille in grondkwaliteit samestelling indien dit vergelyk word met die omliggende, gewone veld en hierdie verskynsel word waargeneem dwarsdeur die studie wat verskillende geologiese formasies verteenwoordig. Die teenwoordigheid van vreemde gesteentes in ‘n betreklik homogene geologiese omgewing word aangedui deur middel van geofisiese profiele en sonderings. Bestaande boorgate in die teenwoordigheid van geobotaniese gemeenskappe, maar ook verwyder daarvan, dui op die belangrikheid van sulke gemeenskappe as hierdie gemeenskappe aan die skerp waarnemer die voorkoms van grondwater aldaar aandui. Hierdie navorsing sluit akwifeerlewering verkry by geobotaniese gemeenskappe in en die gemiddelde lewering van akwifere in dieselfde geologiese omgewing, waar die meeste boorgate geboor is sonder die insluiting van geobotaniese aanwysers. Laastens, die waarde van grondkwaliteitmonsters word bespreek met ‘n voorkeur vir KUK-waardes om geobotaniese gemeenskappe mee aan te dui en/of die teenwoordigheid van grondwater. Die statistiese behandeling van die data dui duidelik daarop aan dat daar ‘n statisties betekenisvolle regressie bestaan tussen geologie, geofisika en grondwater as die verklarende veranderlikes en KUK en geobotanie as die afhanklike veranderlikes.
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Keywords
Thesis (Ph.D. (Geohydrology))--University of the Free State, 2007, Geomorphology -- South Africa. Physical geography, Plant indicators -- South Africa, Groundwater -- South Africa, Aerial photographs, Cation exchange capacity (CEC), Soil series, Case studies, Regression analysis, Statistically significant, Geohydrology, Geophysics, Geobotany, Physical geography
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