TRANSBOUNDARYSTAMPRIET ARTESIAN AQUIFER

A Namibian Over- and Review

Development History – Knowledge Status Problems and Potential Solutions

Jürgen Kirchner & Gideon Tredoux

Osterode Süd 1967

Artesian Borehole

SAB within ORASECOM

Stampriet Artesian BasinGroundwater Control Area

SHEEP FARMING

Cour

tesy

Agr

iFor

um

and IRRIGATION

Irrigation 46%

Domestic 16%

Stock Watering 38%

Wide Valley –Tiny River

Coarse Conglomerate

100 YEARS of INVESTIGATIONS• Paul Range discovered the SAB in 1912• Frommurze investigated in the 1930s• H. Martin researched for the Coal Report• K. Schalk investigated a cloud break in 1960• Geochemistry, Geohydrology, Isotopes

(Tredoux, Kirchner & Vogel in the 1970s)• Oil and Coal exploration (1960s – 1980s)• J. Nawrowski explored Abstraction and

Irrigation (1980s - 1990s)• JICA GW Evaluation & Management (2002)• IAEA RAF 8/029 (Isotope studies, 2002)• Bäumle: Stampriet Groundwater Model (2005)

GRIM located about 180 documents with60 attached

N-S Section by Henno Martin along Botswana Border (1956)

FENCE DIAGRAM

Stratigraphy

OLDand

NEW

add “Neu Loore”

10km East of Mariental 15km East of Mariental 6km East of Mariental 18km East of Mariental 20km South of Mariental 25km East of Gibeon 20km East of Asab 50km North of Keetmanshoop

1205m 1205mASL 1205mASLASL Pale brownishi grey calcrete Pale brownishi grey calcrete

-containing basalt pebbles and boulders -calcrete breccias at the base -calcrete breccias at the base

1200m 10-15m 10m 1200mASL1m+ Grey very coarse sandstone

(30m) -silicified -weathered biotite rich

2m+ Grey medium sandstone(24m) -bedded well

-weathered biotite richBrown coarse sandstone

2m -bedded well -strongly weathered

1195m -pisolitic structures(1-2 in sizes) 1195mASLAmygdaroidal basalt Brown fine sandstone 1m Reddish brown coarse sandstone Pale brownishi grey calcrete -calcites in pores Purple very coarse sandstone -containing basalt pebbles and boulders -irregular fractures developed well 3m -calcrete breccias at the base -bleaching in the weathered crusts Greenishi grey coarse sandstone

-weathered biotite rich4m

Greenish grey shale -oxidized -brown to dark grey in original colors

1190m -gypsum 10-15mReddish brown very coarse sandstone -borrow structures developed well -weathered biotite rich

4m -water leaking

30m+ Greenish grey shale1185m unknown -weathered biotite rich

Dark grey coarse sandstone -calcareous -cross bedding developed well -concretions

5m

25-30m

1180mPale grey fine to medium sandstone -cross bedding developed well -weathered biotite rich

5m

1175mBrown medium sandstone 1-2m Pale grey siltstone -squized structures at the boundaries -weathered biotite rich Pale grey coarse sandstone -bedded well -dark grey in weathered surface

-concretions

5m

1170m 10m 1170ASLPale brownishi grey calcrete -containing basalt pebbles and boulders

Brownish grey medium sandstone -calcrete breccias at the base -bedded well -very strong against weathering

1165m 7m 1065mASLDark grey coarse sandstone Dark grey shale -calcareous unknown -white in weathered surface -cross bedding developed well -concretions

5-10m 15m Coarse doleriteunknown -sill like structure

0.3m Greenish grey siltstone1160mASL

Greenish grey shale Dark grey shale1160m Dark grey coarse sandstone -water leaking unknown -greenish grey in weathered surface

Brown medium sandstone -calcareous -cross bedding developed well -cross bedding developed well -weathered biotite rich -concretion Coarse dolerite

unknown -sill like structureBrown medium sandstone -cross bedding developed well

5m -ripple marks Dark grey shale -concretions -greenish grey in weathered surface

unknown1155m

Yellowish grey shale

1m Grey fine sandstone -cross bedding developed well

15m 20-25mAlternating beds of brownish grey

3m shales and brownish grey shales -cross bedding developed well -ripple marks 1150mASL

1150m -weathered biotite rich 0m Gravels of pale brownishi grey calcretes

Grey coarse sandstone 2m Pale grey very coarse sandstone2m -light grey at weathered surface -weathered strongly

-concretions -massive15m

Dark grey coarse sandstoneDark grey siltstone -weathered biotite rich

2m -concretions(1-10m in sizes) -cross bedding developed well -slunping structure developed well -borrow structure developed well

1145m -joints developed0.5m Greenish grey siltstone -water leaking 6m

-slunping structure developed well 2mGrey medium sandstone

Greenish grey shale -pisolitic structures(1-2 in sizes) -low resistance against weathering -slunping structure developed 2m+ Dark grey shale

- variation in thicness Alternating beds of grey mediumand grey coarse sandstones -bedded well

1140m -borrow structure developed poorly10m+ Very dark grey to black shale

-original color

7m

1135m 10mGrey coarse sandstone -coaly fragments -borrow structure developed well -showing terrace like tpopgraphy

6m

1130mDark grey coarse sandstone

2m -concretions -showing terrace like tpopgraphy Alternating beds of grey fine to medium

sandstones and grey shalesYellowish grey medium sandstone -bedded well

2m -unsorted -borrow structure developed well

0.2m Grey coarse sandstone 6m1125m

2m Yellowish grey medium sandstone -bedded well -cross bedding developed well -concretions at base

0.5m3m Alternating beds of grey siltstones 0.2m Dark brown coarse sandstone

and grey fine sandstones -lens like structure -bedded well -ferruginous

1120m 1-2m Dark grey coarse sandstone -basal conglomerate(0.3-20cm in size) Very dark grey shale -showing terrace like tpopgraphy -grey in weathered surface

1m+Greenish grey shale

1115m 14m

1110m

Very coarse sandstones Kalahari Group 1205m Approximate elevation above sea level ASL delived from 1:250,000 topographic maps

Coarse sandstones Kalkrand Formation 1m Dark grey coarse sandstone -calcareous

Medium sandstones Intrusives of Dolerite sills 1200m -concretions -basal conglomerate

Fine sandstones Whitehill Formation1105m 10m Thickness of strata 4m+ Greenish grey shale

Siltstones Auob Member* Discription

Shales Prince Albert Formation

Calcretes Nossob Member

Basalts Dwyka Formation

Dolerites1100m

LEGEND

Geology of Namibia

Roy Miller’s book displays the

pre-Kalahari river network of the

Stampriet Artesian Basin

Water Quality Map

TDSSO4

NO3F

The South West Africa Steering Committee for Water Research initiated a Water Quality Map Project in the late 1960s. In the SAB about 4000 water points were sampled and other borehole and water use information collected.

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Hydrocensusc CHECK# Des#S NU# U

2 holes390 holes955 holes

4915 holes

Stampriet Artesian Basin

HydroCensus Results (2002)

DISTRIBUTION OF

BOREHOLES

Groundwater Levels & Flow

%

%

%

%

%

%

%

%

%

%

%%

%

%

%

%

%

%

%

%

%[

%[

%[

%[

%[

%[

#Y

#Y#Y

#Y#Y#Y

#Y#Y#Y

#Y

#Y#Y#Y

#Y#Y

#Y#Y#Y

#Y

Gobabis

Rehoboth

Kalkrand

Windhoek

Mariental

Leonardvil le

Tses

Koes

Dobbin

Mentz

Gochas

Schlip

Tsumis

Gibeon

Aranos

Aminius

Genesis

Corridor

Komnarib

Duineveld Hoachanas

Stampriet

Mata-Mata

Uhlenhorst

Wandervogel

Klein Vaalgras

J-1

J-2

J-3

J-4

J-5

J-6

J-7

J-9

1150

1100

1200

105

0

1250

100

0

950

1300

950

1250

1150

1 050

1150

1050

1250

1150

1200

1000

J-8Piezometric Head of Auob1350 - 14001300 - 13501250 - 13001200 - 12501150 - 12001100 - 11501050 - 11001000 - 1050950 - 1000900 - 950850 - 900

Piezometric of Head of AuobRoadMain Road

% Town%[ Main Town#Y JICA Test BH

Study Area

N

EW

S

0 20 40 (Km)Piezometric Head of Auob Aquifer

26° 26°

25° 25°

24° 24°

23° 23°

18°

18°

19°

19°

20°

20°

%

%

%

%

%

%

%

%

%

%

%%

%

%

%

%

%

%

%

%

%[

%[

%[

%[

%[

%[

#Y

#Y#Y

#Y#Y#Y

#Y#Y#Y

#Y

#Y#Y#Y

#Y#Y

#Y#Y#Y

#Y

Gobabis

Rehoboth

Kalkrand

Windhoek

Mariental

Leonardvil le

Tses

Koes

Dobbin

Mentz

Gochas

Schlip

Tsumis

Gibeon

Aranos

Aminius

Genesis

Corridor

Komnarib

Duineveld Hoachanas

Stampriet

Mata-Mata

Uhlenhorst

Wandervogel

Klein Vaalgras

J-1

J-2

J-3

J-4

J-5

J-6

J-7

J-9

J-8

1100

1200

950

1350

1050

1150

1300

1000

1250

1250

1050

10 5

0

100

0

1200

1150

1200

1000

1000

N

EW

S

Piezometric Head of Kalahari1350 - 14001300 - 13501250 - 13001200 - 12501150 - 12001100 - 11501050 - 11001000 - 1050950 - 1000900 - 950850 - 900

Piezometric Head of kalahariRoadMain Road

% Town%[ Main Town#Y JICA Test BH

Study Area

0 20 40 (Km)

26° 26°

25° 25°

24° 24°

23° 23°

18°

18°

19°

19°

20°

20°

Kalahari Auob

Kalahari: redAuob: black

WATER LEVELS

1 8 1 9 2 0- 2 6

- 2 5

- 2 4

- 2 3

PCI data set

Existing Recorder Network

Recorder BH

Gomchanas Recorder

Gomchanas M122: Ex-DWA Analog Recorder (WW8399) - Auob Aquifer

-10.00

-5.00

0.00

5.00

Jan

-74

Jan

-75

Jan

-76

Jan

-77

Jan

-78

Jan

-79

Jan

-80

Jan

-81

Jan

-82

Jan

-83

Jan

-84

Jan

-85

Jan

-86

Jan

-87

Jan

-88

Jan

-89

Jan

-90

Jan

-91

Jan

-92

Jan

-93

Jan

-94

Jan

-95

Jan

-96

Jan

-97

Jan

-98

Jan

-99

Jan

-00

Jan

-01

Jan

-02

Jan

-03

Jan

-04

Date

Wa

ter

Le

vel (

mA

GL

)

Replace Analog Recorder with Digital RecorderDL Serial Number: F4483 Installation Date: 21/08/2001

UHLENHORST CLOUD BREAK

Schalk investigated the extraordinary rainfall event in the night of 24 February 1960. A borehole on Klein Swartmodder 50 km away started flowing three weeks later with a head of 1.3 m

Ja DennochPaddington

Klein Swartmodder

We do have such events from time to time

Mariental flood 2006

SAB 2000 (left)

SAB 2001 (right)

SINKHOLE RECHARGE I

• Field observations show that rainwater flows towards these depressions where it seeps away within hours.

• Calcrete at the perimeter and below the sinkhole is karstified in the process. In the centre impermeable material is deposited.

15 hours after between 60 and more than 100 mm of rain fell. Note the drift material (left) and the tiny puddle in the back.

SATELLITE IMAGE : SINKHOLES

SINKHOLE DISTRIBUTION

• In the west and the north-west Kalahari sinkhole features can be recognised over large areas (they continue further south).

• Some lie in the confined parts and can only contribute to Kalahari recharge.

• No sinkholes have been identified in the north-eastern parts of the basin.

Leon ardv il le

A m in u isU h l en h o r st

A ran os

Stampriet

G o c h a s

MA RI EN TA L

? ?

Leon ardv il le

A m in u isU h l en h o r st

A ran os

Stampriet

G o c h a s

MA RI EN TA L

? ?

SODIUM ADSORPTION RATIO

SAR ratios of artesian (solid colour) and

subartesian boreholesGenerally better quality in the

western (Cisnossob) half of the basin

14CApparent

Age

Young Auob water in the CisNossob

20 000 years older water in the

TransNossob

18° E 19° E 20° E

18° E 19° E 20° E

26° S

25° S

24° S

23° S

0 25 50 75 100

G ochas

S tam priet

M ariental

Koës

Aranos

Leonardville

Am inuis

Kalkrand

Hoachanas

U hlenhorstB lum fe lde

km

D excess (per m il)

-10

-5

0

2

3

4

5

8

10

20

Procla im ed SAB

18° E 19° E 20° E

18° E 19° E 20° E

26° S

25° S

24° S

23° S

0 25 50 75 100

G ochas

S tam prie t

M arienta l

Koës

Aranos

Leonardville

Am inuis

Kalkrand

H oachanas

U hlenhorst

B lum fe lde

km

D excess (per m il)

P rocla im ed SA B

-10

-5

0

2

3.5

5

8

10

20

Deuterium ExcessKalahari Auob

Recharge areas

Auob River

NAMIBIA

Approximate Orange – Okavango

Watershed

Nossob River

?

RSA

BOTSWANA

Wei

ssra

nd

Auo

b Nossob

NE

Am

inui

s

No indication of recharge from NE

Paleoclimateconcepts

(Vogel - Heine)

ARCHEOLOGICAL CLASSIFICATION

Age range [ky B.P.]

Namib Vogel (1989)

Lowland Heine (1992)

Highland Heine (1992)

HISTORICAL TIME 0-1

IRON AGE -2

BRONZE AGE -3

-4

-5

-6

-7

-8

BOREAL -9

PREBOREAL -10

-11

-12

-13

-14

-15

-16

-17

-18

-19

-20

-21

-22

-23

-24

-25

-26

-27

-28

-29

-30

-31

-32

-33

-34

-35

Arid climate Present climate

After GEYH (1994) Humid climate

MIDDLE PALEOLITHIC

HO

LO

CE

NE

PL

EIS

TO

CE

NE

SUBATLANTIC

SUBBOREAL

ATLANTIC

MIDDLE WEICHSELIAN

LATE WEICHSELIAN

STRATIGRAPGICAL CLASSIFICATION

NEOLITHIC

MESOLITHIC

YOUNGER PALEOLITHIC

• Schalk (1960) calculated the amount of water that infiltrated after the cloudburst as approximately:

Q = 100 * 106 [m3]

but did not estimate the proportion that might have reached the artesian aquifers.

• The artesian water abstraction then was estimated at

44 000 m3/d or 16 * 106 [m3/a]

SAB RECHARGE (Schalk)

• Vogel et al. (1982) applied Darcy’s Law:Q = kD * b * i [m3/d]

using an average gradient i = 1/1000, an average transmissivity kD = 11.3 m2/d and an aquifer width b = 55 km above Stampriet. This resulted in an average annual recharge rate for the Stampriet surrounding of:

Q = 0.68 * 106 [m3/a]

SAB RECHARGE (Vogel et al.)

• PCI (2002) have calculated the combined recharge for all three aquifers using different approaches:

1. Modeling (a)1): 21 * 106 [m3/a]2. Modeling (b): 87 * 106 [m3/a]3. Water Balance (a): 105 * 106 [m3/a]4. Water Balance (b): 341 * 106 [m3/a]5. Water Balance (c): 1 550 * 106 [m3/a]

The 4 to 15 times varying values allow not to decide on a correct mean recharge rate.

SAB RECHARGE (PCI)

1) Modeling 1: ordinary year; 2: 1:50 year. Balance excluding losses (a): ordinary year CMBM, (b): 1:50 year CMBM, (c): 1:50 year assuming normal transpiration, withdrawal & groundwater flow

Abstraction in m3/d

(JICA, 2000)

Block size about 275 ha

%

•

•

•

•

•

•

•

•

••

••

•

•

•

•

•

•

Kalkrand

Mariental

Leonardville

TsesKoes

Dobbin

Mentz

Gochas

Gibeon

Aranos

Aminuis

Genesis

Corridor

Komnarib

Duineveld Hoachanas

Stampriet

Mata-Mata

Uhlenhorst

Wandervogel

Klein Vaalgras

N

EW

S

Intensity of Withdrawal-K0- 1010 - 3030 - 5050 - 100100 - 500500 - 10001000 - 20002000 - 5000

RoadMainRoad

•

MainTown• Town

AminuisStudy Area

Unit; m3/day

Unit; m3/day

0 30 60 90 (Km)

•

•

•

•

•

Abstraction from the 3 Aquifers(after JICA)

AquiferAbstraction

[Mm3/a]%

Kalahari 9.80 65.5Auob 4.97 33.2Nossob 0.20 1.3TOTAL 14.97 100.0

Long-term OverabstractionSpes Bona Recorder

1160.00

1162.00

1164.00

1166.00

1168.00

1170.00

1172.00

1174.00

1176.00

1178.00

1180.00

1978

/01/

01

1979

/01/

01

1980

/01/

01

1981

/01/

01

1982

/01/

01

1983

/01/

01

1984

/01/

01

1985

/01/

01

1986

/01/

01

1987

/01/

01

1988

/01/

01

1989

/01/

01

1990

/01/

01

1991

/01/

01

1992

/01/

01

1993

/01/

01

1994

/01/

01

1995

/01/

01

1996

/01/

01

1997

/01/

01

1998

/01/

01

1999

/01/

01

2000

/01/

01

2001

/01/

01

2002

/01/

01

2003

/01/

01

2004

/01/

01

Date

Wat

er l

evel

(m

amsl

)

We know too little . . .

• Water levels are dropping• Consumption and Losses rise

Spes Bona0.00

2.00

4.00

6.00

8.00

10.00

12.00

1960 1965 1970 1975 1980 1985 1990 1995 2000

Wa

ter

lev

el

BOOMPLAAS Recorder

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

01-0

7-70

01-0

7-72

01-0

7-74

01-0

7-76

01-0

7-78

01-0

7-80

01-0

7-82

01-0

7-84

01-0

7-86

01-0

7-88

01-0

7-90

01-0

7-92

01-0

7-94

01-0

7-96

01-0

7-98

01-0

7-00

Date

Wat

er le

vel [

met

res

bel

ow

su

rfac

e]

IrrigationDomestic

Stock WateringThere is an urgent need for

CONTROLand

REMEDYBoth need to be placed on sound

footing

CONSTRAINTS I

AQUIFER PROBLEMS• Largely “semi-accurate” elevations• Aquifer identification in boreholes• Leaking seals of (sub)artesian holes• Regional variation of target aquifers• Lacking water levels and• Water-level dates varying• Lacking abstraction data• Deteriorating water quality• Changing stratigraphy• Lacking knowledge

CONSTRAINTS II

ADMINISTRATIVE PROBLEMS• Drilling control (depth, seals)• Unauthorised drilling• Irrigation allocation (quantity)• Abstraction (control, returns)• Unauthorised abstraction• Wastage (leaking pipes, etc.)• Electronic data capture (staff)

Some permanent problems… Corrosive water and …

…Farmers not caring to waste artesian water

Leaking Borehole

-35.00

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

Wa

ter

Le

vel (

mb

gl)

09/09/77 @12H25; DGR=9.68m - measured by T. da Silva

09/09/77 @ 14H00; DGR=27.27m - measured by T. da Silva "complete maintance BH, water sample"

Approximate position of Boomplaas Recorder

Auob W-L

Kalahari W-L

Estimated 20 - 25 m drop of Water-level(Auob leaking into Kalahari)

Proposed Actions1. TRANSNOSSOB• Find or drill suitable Boreholes (use Miller’s analysis)• Identify Aquifer, determine W-L, Quality, Isotopes

– Use Geochemical logs, Packer sampling• Establish Flow pattern and Recharge Area2. Whole SAB• Do Pumping tests for Aquifer Constants• Repeat 2001 Water-level Survey• Drill borehole to close knowledge gaps• Model or otherwise establish Abstraction Potential of

“Irrigation Areas”.• Investigate Leakage (natural – boreholes)• Develop and implement Policy

– Applications, Permits, Drilling, Abstraction, Leakage, Pollution/Wastage, Fees, Tariffs, Policing, Penalties)