Hydrogeology in the Hydrogeology in the Limpopo BasinLimpopo Basin

Overview of key hydrogeological Overview of key hydrogeological units in the Limpopo basin in units in the Limpopo basin in

Mozambique, South Africa and Mozambique, South Africa and ZimbabweZimbabwe

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Why Hydrogeological UnitsWhy Hydrogeological Units Insight into groundwater potential for the Insight into groundwater potential for the

basinbasin In sight of where to apply water conservation In sight of where to apply water conservation Because water conservation is affected by Because water conservation is affected by

hydro geological units’ characteristics such ashydro geological units’ characteristics such as storage capacity ( porosity related)storage capacity ( porosity related) residence time (underlying units related)residence time (underlying units related) thickness of the weathered overburden (direct thickness of the weathered overburden (direct

relationship between water yielded to thickness) relationship between water yielded to thickness)

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Geology of Limpopo basin in MozaGeology of Limpopo basin in Moza

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31.5° 32° 32.5° 33° 33.5° 34° 34.5°

31.5° 32° 32.5° 33° 33.5° 34° 34.5°

-25.5°

-25°

-24.5°

-24°

-23.5°

-23°

-22.5°

-22°

-21.5°

-25.5°

-25°

-24.5°

-24°

-23.5°

-23°

-22.5°

-22°

-21.5°

conglom erates, silts in terca lated w ith m arine sands

CRETACEOUS

K A R O OJURASSIC

QUATERNARY &RECENT

R ecent a lluvium C oasta l dunes, m obile dunes

Interior dunes, consolidated dunes includ ing rem obilised & longitudanal

arg illites, areanous fluvia l sandstones & m udstones, other superfic ia l deposits

arg illites re lated to m arine terrraces

Ferrigenous arid sands

m ixed calcerious sands

conglom erates in terca lated w ith vo lcanics of Karoo age

rhyolites

S E N A

E LE FA N TE S /S IN G U E D EZE

C H E R IN G O M A

M A ZA M B AM IOCENE

PALEOCENE

GEOLOGICAL LEGEND

C haila

M A N JA C A ZE

C higubo

M achaila

C H IC U A LA C U ALA

M A SSIN C IR

D indiza

XA I-XA I

M A N H IC A

M A G U D E

C H O KW E

G U IJA

L i m p o p o R

i v e r

S a v e R i v e r

Mozambique Hydrogeology Mozambique Hydrogeology

mostly sedimentary rocks or unconsolidated mostly sedimentary rocks or unconsolidated sediments, with minor hard rock lithologies.sediments, with minor hard rock lithologies.

primary porosity aquifers with high groundwater primary porosity aquifers with high groundwater storage capacity.storage capacity.

Coarse grained sediments give abundant Coarse grained sediments give abundant groundwater; fine grained sediments are poor groundwater; fine grained sediments are poor aquifers. aquifers.

Coastal regions and areas along the main river Coastal regions and areas along the main river channels are most promising. channels are most promising.

Regular recharge is important in terms of ensuring Regular recharge is important in terms of ensuring good fresh water quality. good fresh water quality.

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The Hydrogeology of the Limpopo Basin in Mozambique.

Period Rock types GroundwaterPotential

Quaternary

Holocene

Pleistocene

Alluvial

Marine / lacustrine alluvials

Very good

Very good

Upper

Tertiary

Lower

Miocene

Palaeocene

Ferrigenous arid sands

Mixed calcareous sands

Very good

Very good

Upper

Cretaceous

Lower135-63 my

Conglomerates + silts + marine sands.

Conglomerates +Karoo volcanics

Silts – poorSands - good

Good

Jurassic 180-135 my Rhyolite, Basalt,alkaline rocks. Very poor.

For the unconsolidated sediments: •Active recharge will be a very significant factor in determining water quality

•Grain size will determine well yields 6/16/20096/16/2009

28° 28.5° 29° 29.5° 30° 30.5° 31° 31.5°

28° 28.5° 29° 29.5° 30° 30.5° 31° 31.5°

-22°

-21.5°

-21°

-20.5°

-20°

-22°

-21.5°

-21°

-20.5°

-20°

O lder G neiss C om plex

Serpentin ite and pyroxenites

D olerites and G abbros

G ranophyre, gran ite and syenite

G neisses of various ages

INTRUSIVE IGNEOUS ROCKS

U ltram afic lavas and in trusions

Basaltic vo lcanics w ith in terca la ted sedim ents

Andestic and dacitic m etavo lcanics

M etasedim ents, fe ls ic m etavo lcan ics

G niesses of various ages

G lacia l beds, m udstones, coal m easures and sandstones

G rits, sandstones and silts tones

Basalt

R hyolite

Sandstone, e tc.

A lluvium and other superfic ia l deposits

CRETACEOUS

KARO O

BEITBRIDG E

SHAM VAIAN

BULAW AYAN

SEBAKW IAN

G REAT DYKE

JURASSIC

TRIASSIC

PERMIAN

EARLYPRECAMBRIAN

VARIOUS AGES

LATE JURASSIC

PLEISTONE &RECENT

Younger granites, granodiorite-adam ellite

TABLE OF FORMATIONS

SYSTEM O RG R O U P

IN TER N ATIO N AL

Geology of limpopo basin in ZimGeology of limpopo basin in Zim

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Zimbabwe HydrogeologyZimbabwe Hydrogeology mostly of crystalline basement igneous and mostly of crystalline basement igneous and

metamorphic rocks. Minor occurrence of sedimentary metamorphic rocks. Minor occurrence of sedimentary rocks in the basin. rocks in the basin.

secondary porosity features such as fracture zones secondary porosity features such as fracture zones and the weathered regolith. and the weathered regolith.

Small scale water supplies available from granitoid Small scale water supplies available from granitoid crystalline lithologies; greenstones are more crystalline lithologies; greenstones are more favourable. favourable.

Karoo lithologies can provide moderate and Karoo lithologies can provide moderate and occasionally large scale groundwater supplies. occasionally large scale groundwater supplies.

Large-scale groundwater supplies restricted to Large-scale groundwater supplies restricted to alluvial aquifers along the major rivers.alluvial aquifers along the major rivers.

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Hydro-geological unit

Main lithologies Groundwater occurrence Average range of borehole depth (m)

Average range of sustainable borehole yield (m3/d)

1 Achaean Granite and Gneissose rocks

Principally in weathered and fractured zones. 10-35m thick

40-50 in African surface. 30-40 on post-African surface

50-100 in African surface. 10-50 in post African surface

2 Greenstone Belts - Bulawayan metalavas and Shamvaian metasediments

Associated with weathering of Bulawayan strata to 50m and fracturing in Shamvaian strata

30-50 in Bulawayan 40-60 in Shamvaian

100-250 or more in Bulawayan 10-25 in Shamvaian

3a

Karoo Sequence has been divided into 5 sub-units.Batoka Basalt

Controlled by weathering and fracturing from 30-70m below surface

40-60 20-100

3b The Forest Sandstone Saturated sandstone generally confined aquifer

50-100 50-300

3c The Escarpment Grit Saturated sandstone and grit. Generally confined except in Zambezi Valley

50-70 100-300

3d The Madumabisa Mudstone

Associated with shallow weathering or sandy intercalations which water strike between 40-70m occur

50-70 10-25

3e The Upper and Lower Wankie Sandstone

Saturated sandstone confined aquifer 100-150 100-500

4 The Cretaceous Sandstones

Deep zones of primary features possibly shallow weathering along drainage lines

70-100 10-50

5 Kalahari sands Saturated unconsolidated sands and consolidated pipe sandstone

70-100 100-1000

6 Alluvial Deposits Primary porosity and permeability in gravel lenses, sand layers

20-70 100-5000

Hydrogeological Units – Limpopo Basin Zimbabwe

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Geology of limpopo basin in S.AGeology of limpopo basin in S.A

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26° 27° 28° 29° 30° 31°

26° 27° 28° 29° 30° 31°

-26°

-25°

-24°

-23°

-26°

-25°

-24°

-23°Sandstones, shale , m udstone, coal

B asa lt, pyroclastics in terca la ted w ith sandstones

R hyo lite , dacite , pyroclastics

S andstone, sha le , lim estone

U nconso lidated superfic ia l deposits, lim estone,cong lom erate , sandstones

M etased im ents

C onglom erate , quartz ite , sha le, lim estone, lavas

U ltrabasic to basic in trusives

M igm atite , gn iess

C onglom erate , quartzite , shale , phylite , tillite , lavas

G ran ite

Q uartz ite , shale, conglom erate, andesite

D olom ite , chert, cong lom erate , quartz ite , sha le , tillite

Q uartzite , shale , cong lom erate

Q uartz ite , sha le , tillite , andesite , chert, jasp ilite , lim etsone

Q uartz ite , sha le , horn fe ls , lavas, pyroclasts, chert, jasp ilite , lim etsone

Q uartzite , shale , hornfe ls , andesite , chert, tu ff, lim etsone, conglom erate

M igm atite , gn iess, h igh grade m etam orph ic rocks

Pyroclastic fe ls ite

G abbro , norite , chrom itite , m agnetite

G ranophyre

G ranites, fe ls ite , tu ffaceous & sha ly sed im ents,agg lom erate

Lava, sandstone, conglom erate , s ilts tone, greyw acke

Sandstone, cong lom erate, s ilts tone

A lka lis , basic to u ltrbasic in trusives, carbonatite

T illite , sandstone, sha le

Shale , sandstone, grits tone, coa l

KAR O O

STO R M BER G

ECC A

D W YKA

KRAN SBER G

N YLSTRO O M

BUSH VELDIN TR U SIVEC O M PLEX

LIM PO PO BELT

PRETO R IA

M ALIM AN I

D O M IN IAN

JURASSIC

TRIASSIC

PERMIAN

PR

EC

AM

BR

IAN

TERTIARY &RECENT

CARBONIFEROUS

W ATER BER G

CRETACEOUS

PILAN SBERG INTR USIVEC O M PLEX

GEOLOGICAL LEGEND

AR C H AEAN G R EEN STO N ES

South Africa HydrogeologySouth Africa Hydrogeology Geology quite complex. Geology quite complex. Quartzites / basal conglomerates (Dominion group) Quartzites / basal conglomerates (Dominion group)

and Karst limestones (Malimani & Pretoria group) at and Karst limestones (Malimani & Pretoria group) at the base of the sequence have high to very high the base of the sequence have high to very high potential. potential.

Crystalline basement complex rocks have low to very Crystalline basement complex rocks have low to very low groundwater potential, except Archean low groundwater potential, except Archean greenstones, which have medium potential.greenstones, which have medium potential.

Indurated and metamorphosed sedimentary rock also Indurated and metamorphosed sedimentary rock also have low potential. Karoo has generally low have low potential. Karoo has generally low potential. potential.

Recent unconsolidated sediments and alluvial Recent unconsolidated sediments and alluvial material have high potential. material have high potential.

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Hydrogeological units of S.A.Hydrogeological units of S.A.

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ConclusionsConclusions

Very varied hydrogeological unitsVery varied hydrogeological units Different GW potentialDifferent GW potential Implication = Different conservations potentialImplication = Different conservations potential Need to expand this to assess potential for Need to expand this to assess potential for

conserving waterconserving water

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Thank youThank you

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