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Hydrogeology in the Limpopo Basin. Overview of key hydrogeological units in the Limpopo basin in Mozambique, South Africa and Zimbabwe. Why Hydrogeological Units. Insight into groundwater potential for the basin In sight of where to apply water conservation
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Hydrogeology in the Limpopo Basin Overview of key hydrogeological units in the Limpopo basin in Mozambique, South Africa and Zimbabwe
Why Hydrogeological Units • Insight into groundwater potential for the basin • In sight of where to apply water conservation • Because water conservation is affected by hydro geological units’ characteristics such as • storage capacity ( porosity related) • residence time (underlying units related) • thickness of the weathered overburden (direct relationship between water yielded to thickness)
Mozambique Hydrogeology • mostly sedimentary rocks or unconsolidated sediments, with minor hard rock lithologies. • primary porosity aquifers with high groundwater storage capacity. • Coarse grained sediments give abundant groundwater; fine grained sediments are poor aquifers. • Coastal regions and areas along the main river channels are most promising. • Regular recharge is important in terms of ensuring good fresh water quality.
The Hydrogeology of the Limpopo Basin in Mozambique. • For the unconsolidated sediments: • Active recharge will be a very significant factor in determining water quality • Grain size will determine well yields
Zimbabwe Hydrogeology • mostly of crystalline basement igneous and metamorphic rocks. Minor occurrence of sedimentary rocks in the basin. • secondary porosity features such as fracture zones and the weathered regolith. • Small scale water supplies available from granitoid crystalline lithologies; greenstones are more favourable. • Karoo lithologies can provide moderate and occasionally large scale groundwater supplies. • Large-scale groundwater supplies restricted to alluvial aquifers along the major rivers.
South Africa Hydrogeology • Geology quite complex. • Quartzites / basal conglomerates (Dominion group) and Karstlimestones (Malimani & Pretoria group) at the base of the sequence have high to very high potential. • Crystalline basement complex rocks have low to very low groundwater potential, except Archean greenstones, which have medium potential. • Indurated and metamorphosed sedimentary rock also have low potential. Karoo has generally low potential. • Recent unconsolidated sediments and alluvial material have high potential.
Conclusions • Very varied hydrogeological units • Different GW potential • Implication = Different conservations potential • Need to expand this to assess potential for conserving water