POLYTECHNIC IWRM-MASTER

PROGRAM

Ben van der Merwe

Environmental Engineering Services

ENVES

STRUCTURE OF THE PRESENTATION

• Water Demand Management

• Artificial Recharge

• Water Demand Forecasting Methods

WATER DEMAND MANAGEMENT

• End use of water (Polytech Project)• Water losses on private properties

(Whk N$ 6 m/annum)• Non-revenue water (N$ 25m+/annum)• Benchmarking according to IWA • Pressure reduction (Major benefits )• Measuring of reduced water use (Modelling)

ARTIFICIAL RECHARGE

• Some results

• Development of groundwater models

• Security of supply

• Benefit costs

• Water quality (modelling)

1640

1644

1648

1652

1656

1660

1664

1668

Wate

r L

evel (m

am

sl)

15-May 14-Jul 12-Sep 11-Nov 10-Jan 11-Mar 10-May 09-Jul

9/8A (Inj. Bh) 9/6 (1201 m NE) 9/9 (787 m N)

9/11 (626 m SW) 9/12 (1180 m SW)

Water levels afterC-filter backflushing

Injection

1998 1999

Volume injected:290 000 m^3

ARTIFICIAL RECHARGE INJECTION INTO BH 9/8A AT 62 KL/H

1678

1680

1682

1684

1686

Wate

r L

evel (m

am

sl)

07-Aug 21-Aug 04-Sep 18-Sep 02-Oct 16-Oct

Bh 12/2 459 mSouth

Bh 12/4 1133 m

East

Bh 12/1A1348 mS-West

Injection

1999

ARTIFICIAL RECHARGE INJECTION INTO BH 12/3 (216 Kl/H)

GROUNDWATER CONTOURS

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5/6

6/36/5 6/6

6/7

6/8

6/9

6/11A 7/17/3

7/47/4A7/6

9/3

9/89/8B

10/1

10/2

10/310/4

10/610/6A

10/7

10/10

10/11

11/7

12/7

13/1A13/1B

13/1C13/4A

15/ 4A

6/3A

9/6A

13/3

2982B08

9/6B

1020

6/8A

7/4B9/3A

10/6B10/2A

10/12

10/1A 12/2A

12/1A

15/115/2

15/315/3A

15/415/4B

15/5

14/1A14/1

14/4A14/414/4B

14/4C

11/911/9A

11/6A11/6

11/8A11/8

11/411/4A

11/1011/11

11/12A11/12

11/5

11/7A

14/3

14/2

13/5

6/11

10/13

12/11

12/112/2

12/412/5

12/6

12/912/9m

12/10

9/69/7

9/9

9/109/10m9/11

9/12

9/149/15

9/17

9/18

9/19

9/20

9/13

3A/13A/4

3B/1

5/4

4/34/2

9/17A

6/10

4 obs

5/5

3757337574

375753757637577

37578

37579

3758037581

37582

37583

37584

37585

37586

37587

37588

Kruinkamp

38814

38817

38815

38816

3A/5

1710#

12/3

#

9/16

#

9/8A

#

9/5

M2

M3K1

9/19/2

6/2

Dawe

1/98

11/2

11/1AGross Windhoek Spring Fissure

Wasserber Springs

Gathemann Spring

1660

M1

B

A

N

Boreholes#

Topographical divideWater level (mamsl)

Legend

$ Springs

2 0 2 Kilometers

22°4

0'

22°40'

22°3

5'

22°35'

17°00'

17°00'

17°5'

17°5'

17°10'

17°10'

CITY OF WINDHOEKDepartment of Infrastructure, Water and Technical Services WINDHOEK GROUNDWATER LEVEL CONTOURS MARCH 2001

Compiled by: E. Murray & G. Tredoux, CSIR, Stellenbosch, RSA.Date: November 2001

SECURITY OF SUPPLY(SWECO)

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0.00 0.10 0.20 0.30 0.40 0.50

Cumulative Probability

Cum

ulat

ive

Sho

rtfal

l (M

m3 /1

0-ye

ars) baseline

Scenario 1

Scenario 2

Tsumeb

Berg Aukas

Demand Management

ECONOMIC COMPARISON

IRR NPV B/C

• Phase 1 30.6% N$ 18.9m 2.33

• Phase 2 29.1% N$ 41.8m 2.71

• Phase 3 14.7% N$ 30.17 2.52

WATER BANKING

0

5

10

15

20

25

30

An

nu

al P

rod

uct

ion

in M

m3

Irrigation

Reclaimed

Surface water

Boreholes

WATER QUALITY

• High DOC values Von Bach

• High TDS Goreangab

• High Sulphates Goreangab

• High Nitrates Goreangab

DEMAND FORECASTING

• Improve methods (TSA with variables)

• Develop more accurate unit water use norms

• Try to measure small changes in demand

CONCLUSIONS

• Scope for applied research • Lowering of water losses major benefit to

Namibia (N$ 21m+/annum)• Start small scale AR projects in rural areas

with water stress and/or bad water quality• Develop ground water models for critical

supply areas• Address groundwater pollution • Establish norms for unit water use • Develop more advanced forecasting models

“When the well’s dry, we know the worth of water”

Benjamin Franklin