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7groundwater quality assessment

7.1General


Water quality is generally determined by solutes and gases dissolved in the water as well as the matter suspended in and floating on it (Fetter, 1994). In this regard, water quality is a consequence of the natural physical and chemical state of the water as well as any alterations that may occur as a result of human activity. The usefulness of water for a particular purpose is determined by its quality. If human activity alters the natural water quality so that it is no longer fit for use for which it was initially suited, the water is said to be polluted or contaminated.

7.2water quality


The term Water quality is used to describe the microbiological, physical and chemical properties of water that determine its fitness for use. Many of these properties are controlled or influenced by substances, which are either dissolved or suspended in water. Therefore, water pollution occurs when water is rendered less fit for use as a result of human activities such as dense human settlements, particularly those with poor sanitation facilities.

Water quality affects the domestic user in terms of:



  1. Health

  2. Aesthetics – the appearance of the water or effects it has on clothes and household fixtures such as baths, and

  3. Economics – replacement of pipes, hot water geysers, etc.

Health effects of water quality on the domestic user include:

  1. Acute effects – ones that can be seen after a very short time.

  2. Chronic effects – those that show only after the water has been used for a long time.

7.2.1Sampling Campaigns


Three sampling campaigns were planned for this project – the first at the end of dry/start of rainy season, the subsequent ones being in the middle and end of the rainy season.

The first sampling campaign was undertaken in mid-November, just before the onset of the rainy season. The other campaigns have been planned for mid-February – during the rainy season – and mid-April (towards the end of the rainy season), respectively, in order to compare the variability of pollutants with varying levels of saturation in the aquifer.

The following parameters were identified for analysis in the first sampling campaign - pH, conductivity, chloride, fluoride, sulphate, nitrite and nitrate, total coliforms and faecal coliforms. The selection of these parameters was because they portray information on the potability of the water as shown in Table 9.

Table 9: Water quality substances of key relevance for domestic use



KEY SUBSTANCES

RELEVANCE TO DOMESTIC USERS

Microbiological quality

Faecal coliforms

Indicates recent faecal pollution and the potential risk of contracting infectious diseases

Total Coliforms

Indicates the general hygienic quality of the water




Physical quality

Conductivity / Total Dissolved Salts

Affects the taste and 'freshness' of the water

pH

Affects the taste and corrosivity of the water




Chemical quality

Chloride

May impart a salty taste to the water

Nitrate and nitrite

May be toxic to infants

Sulphate

Excessive amounts cause diarrhoea

7.2.2Analytical Results


Results of the first sampling campaign as are shown in Table 10 below. The water points from which the samples where collected are shown in Fig. 29.

The most important water quality problem in the project areas of John Laing and Misisi is that of faecal pollution together with the associated disease-causing organisms. In addition, conductivity, which is indicative of elevated salt concentrations (TDS, Sulphate and Chloride) are common.



Faecal pollution

High faecal and total coliform counts (used as indicator organisms for recent faecal pollution) occur in most water points in the settlement.



Conductivity (TDS)

Water sources in the settlements, particularly John Laing, have high values of conductivity (and thus TDS) which appears to result mostly from high chloride, nitrate and sulphate concentrations. A plot of conductivity against concentration of other parameters – Chloride, Sulphate, Nitrate and Phosphate – indicates linear correlations between conductivity and the four quality variables considered (Fig. 30).



Sulphate and Chloride

Water with high conductivity (high TDS) also tends to have high sulphate and chloride concentrations as indicated in these analyses. Sulphate removal is expensive (desalination or ion exchange) and normally not considered viable.



Table 10: Results of the first sampling campaign in the project areas of Lusaka, November 2003

1 JOHN LAING

GPS INFORMATION

PHYSICAL CHEMICAL RESULTS

MICROBILOGICAL RESULTS




Eastings

Northings

pH

Conductivity (S/cm)

Chlorides (mg/l)

Nitrate (as NO3-N mg/l)

Nitrite (as NO2-N mg/l)

Ammonia (as NH4-N mg/l)

Sulphate (mg/l)

Total Phosphates (mg/l)

TC (No/100ml)

FC (No/100ml)

Locality

636010

8292405

7

1236

7

10.2

0.84

0.3

55.6

2.89

26

6

Islamic Borehole - 4

636089

8292396

7.2

1345

174

10.8

0.37

0.18

49.5

2.79

TNTC

TNTC

Shallow well

635664

8292298

7.3

1401

79

3.8

0.068

0.09

28.4

2.99

12

5

Islamic Borehole -2

 

 

7.3

1400

81

3.82

0.066

0.09

28.2

3.09

10

4

Islamic Borehole -2 Duplicate

635673

8292371

7.3

1446

6

11.6

1.058

0.28

30.9

3.01

TNTC

TNTC

Shallow well near islamic borehole - 2

635847

8292190

8.1

1063

80

16.1

2.625

1.78

28

4.98

TNTC

TNTC

Shallow well in depression

635613

8292121

8.2

1177

81

18.8

0.873

0.1

27.5

5.38

120

66

Mutenje Bar

635526

8292177

7.2

1408

100

24.9

0.868

2.59

35.9

5.55

TNTC

TNTC

Near Dollose

635407

8292002

8.1

1044

70

19.3

0.554

1.91

17.4

4

TNTC

TNTC

Near Tafimbwa Lubilo School

635339

8291745

8.2

765

39

11.8

0.265

<0.01

11.5

4.07

TNTC

TNTC

Near Chanda Bar

635190

8291700

8.4

652

44

10.8

0.69

<0.01

5.8

3.48

400

160

Yellow House

635076

8292133

8.2

1371

110

18.1

1.46

3.88

26.6

4.13

TNTC

TNTC

Kapumuleni Mini Mart

634984

8292328

7.2

1120

77

16.3

0.23

0.15

57.5

5.49

0

0

Salvation Army BH

 

 

7.2

1107

79

16.8

0.28

0.19

54.2

6.13

0

0

Salvation Army BH1 (Duplicate)

635318

8292417

8.2

1489

125

23.6

1.344

1.95

34.9

4.54

250

47

Near Twiza

635344

8292368

8.2

1962

149

20

2.804

4.08

45.4

4.52

300

122

Near Twiza 2

635384

8292302

8.5

1686

144

18.3

0.32

2.12

33.9

4.25

0

0

Near Twiza 3

635512

8292435

8.1

1228

84

17.3

0.314

0.35

38.3

6.03

TNTC

TNTC

Near Salvation Army, with reeds

-

-

8.1

1225

80

17.8

0.173

0.37

37.8

5.91

0

0

Salvation Army Bolehole 2

635732

8291942

7.4

679

44

-

0.019

0.03

-

-

0

0

Political borehole

 

 

7.3

676

49

35.2

0.019

0.02

4

1.21

0

0

Political borehole (Duplicate)

Table 10 (continued): Results of the first sampling campaign in the project areas of Lusaka, November 2003



Eastings

Northings

pH

Conductivity (µS/cm)

Chlorides (mg/l)

Nitrate (as NO3-N mg/l)

Nitrite (as NO2-N mg/l)

Ammonia (as NH4-N mg/l)

Sulphate (mg/l)

Total Phosphates (mg/l)

TC (No/100ml)

FC (No/100ml)

Locality

635247

8292244

7.1

1413

157

38.8

1.677

6.13

9

1.78

TNTC

TNTC

Near new saloon and barbershop

635274

8292607

6.8

1043

92

38.8

0.579

0.44

19

1.67

TNTC

TNTC

In caverns

635476

8292545

6.9

1032

92

36.9

0.532

1.62

39

1.79

150

30




635585

8292563

6.9

1035

92

35.1

0.599

1.66

37

1.96

TNTC

TNTC




635660

8292592

7.2

1056

103

39.53

0.541

0.47

18

1.67

TNTC

TNTC

Bambe Grocery

635746

8292608

6.9

1187

106

34.5

0.528

3.32

58

1.48

170

90




2 MISISI COMPOUND

637216

8293553

6.2

610

28

15.5

2.24

0.71

42.5

1.05

TNTC

TNTC

Chairman's place

 

 

6.6

574

23

18.8

1.83

0.84

39.3

0.95

TNTC

TNTC

Chairman's place (Duplicate)

637230

8293043

6.7

771

45

16.5

0.4

1.08

60.1

1.04

26

5

Mississi Bole hole

637125

8293209

6.8

1340

107

15.4

0.8

3.96

74.6

1.52

TNTC

TNTC

Mr. Mwiinga's well

3 MASS MEDIA

642286

8296393

6.9

679

20

7.6

<0.001

0.03

21

1.56

20

3

From Tank; mass media

642971

8296316

6.6

711

25

11.5

<0.001

0.05

52.7

0.83

0

0

Near kalingalinga Bus stop

641630

8296640

6.6

676

19

7.9

<0.001

0.01

20.2

1.54

0

0

International School

641455

8296624

6.6

632

20

7.5

<0.001

<0.01

20.4

1.5

0

0

International School C

641864

8296794

6.6

690

18

7.8

<0.001

<0.01

23.2

1.85

0

0

International School 6E

642340

8296271

6.5

683

18

8

<0.001

0.01

25.3

2.12

0

0

Mass Media 3

Fig. 29: Location of water points sampled during the first campaign


Fig. 30: A regression plot to show the relationship of conductivity to chloride, nitrate, sulphate and phosphates in the Lusaka project areas.


7.3Safety of water for domestic use


Decision making on the suitability of water for domestic use is largely determined by the health problems related to drinking the water.

Records of cholera outbreaks in Lusaka, in general, and the project areas, in particular have already indicated an upswing since it broke out at the start of November – just before the onset of the rainy season. As at 30 January 2004, 2,482 cases of cholera had been reported for Lusaka alone with 110 deaths (see Box 1).


frame25

7.4Sensitisation, educational and awareness programmes


This study will be used to establish the type, extent, and vulnerability to pollution of the aquifer to pollution in the project areas and the possible link between consumption of this contaminated water with the occurrence of certain ailments/outbreaks.

Therefore, with data acquired from this research, a bulletin will be issued to the Ministry of Health and other concerned institutions to enable them formulate short- to medium-term community-based sensitisation and educational awareness campaign programmes on the connections between the state of the aquifer and health status of the city’s citizens.


8REFERENCES AND BIBLIOGRAPHIES


Central Statistical Office. 1990: 1990 Census of population, Housing and Agriculture – Preliminary report, 17pp, Lusaka.

Drysdall, A.R. (1960): The Geology of Lusaka. Rec.Geol.Surv.Northern Rhodesia, pp6-25

Lusaka City Council (LCC) & Environmental Council of Zambia (ECZ), 1997: Solid waste management master plan project for the city of Lusaka. Phase 1 – Diagnosis Final Report

Fetter, C.W. (1994): Applied Hydrogeology. 3rd Edition. MacMillan College Publishing Company. NewYork; Maxwell MacMillan Canada, Maxwell MacMillan International New York-Oxford-Singapore-Sydney.



Gibb Eastern Africa (1999): Final Report on Hydrogeological Investigations and Borehole inspections, Rehabilitation and test pumping. North-West Lusaka Water Project

GRZ/Ministry of Health (1991): National Health Policies and Strategies (Health Reforms). Planning Unit.

Headworth, H.G. (1983): The influence of urban development on groundwater quality. In; Groundwater in Water Resources Planning, vol.1, pp233-243, Koblenz, FRG.

Nkhuwa, D.C.W. 1996: Hydrogeological and Engineering Geological problems of urban development over karstified marble in Lusaka. Mitt.Ing. –u. Hydrogeol., Heft 63, 251S, Aachen

Nkhuwa, D.C.W. 1997: Waste disposal practices and the state of environmental health in Lusaka. Paper presented at the National Conference on Science and Technology on ‘The Role of Science and Technology in socio-economic development in Zambia’, 26-30 August 1997, Lake Kariba Inns, Siavonga.

Thornthwaite, C.W. & Matther, J.R. (1955): The water balance. Inst. Technology, Publ.Climate, 8, No.1, pp1-86

Ubell, K. (1961): Groundwater recharge by direct infiltration of rainfall. Int.Ass.Scien.Hydrol., Publ. 57, 586-596, Gentbrugge

Veihmeyer, F.J. (1964): Evapotranspiration. In Chow, Ven Te (Ed.); Handbook of applied Hydrology - a compendium of water-resources Technology. McGraw-Hill Book Company New York, San Francisco, Toronto. London.

Von Hoyer, M., Köhler, G. & Schmidt, G. (1978): Groundwater and Management Studies for Lusaka. Water Supply. Part 1, Groundwater Study. Hannover; B.G.R., 5 volms.



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