"GROUNDWATER QUALITY IN THE FANLING-SHEUNG SHUI AREA:
A CHEMICAL AND PERCEPTION STUDY"
A THESIS SUBMITTED AS PARTIAL FULFILMENT FOR
THE DEGREE OF MASTER OF PHILOSOPHY
BY
YUEN Yuk-man
May, 1983
DIVISION OF GEOGRAPHY
GRADUATE SCHOOL
THE CHINESE UNIVERSITY OF HONG KONG
CERTIFICATE
I declare that this thesis represents my own work and it has not been previously submitted to this or any other institution in
application for admission to a degree, diploma or other qualification.
yuen yuk
YUEN Yuk-man 3
Abstract of Thesis entitled
GROUNDWATER QUALITY IN THE FANLING-SHEUNG SHUI AREA: A CHEMICAL AND PERCEPTION STUDY
Submitted by YUEN Yuk-man for the Degree of Master of Philosophy at the Chinese University of Hong Kong in May 1983
The chemical quality of groucdwaterin the Fanling-Sheung Shui anling area and the local well users' perception of groundwater pollution were studied between July 1980 and January 1981. The study area covered the whole drainage basin of River Indus where groundwater was commonly used for drinking, domestic and irrigation purposes. A total of 215 wells from 75 villages were selected for water sampling. The data about the well users' perception of groundwater pollution were obtained by face-to- face interview with the owners of the wells selected for this study.
The results indicate that groundwater in the Fanling-Sheung Shui area is slightly acidic with Ca, Na,.Cl and HCO3 as the most abundant ions
No distinct pattern of spatial variation in groundwater quality can be
found. The chemical quality of groundwater in greater part of the study
area is satisfactory for various uses other than drinking due to the presence of excessive amount of NO3-N and heavy metals. Although no case
of methemoglobinemia caused by excessive amount of nitrates or illness
attributed to high levels of. heavy metals in the drinking water have been
reported in Hong Kong, it is necessary to caution the public, especially
the well users, of such problems.
Of groundwater, tap water and stream water, groundwater is
perceived as the cleanest water source. Most of the users are moderately 4 or highly concerned about the problem of groundwater pollution but they cannot correctly assess the quality of the groundwater and have under- estimated the level of pollution. The discrepancy between the actual and perceived quality may be partly explained by some of the respondent's socio-economic characteristics such as education level and occupation.
Users' underestimation of,the pollution levels can affect their behaviour
towards the use of groundwater. They generally ignored the pretreatment of the water before consumption and were not motivated to apply for metered water supply. 5
ACKNOWLEDGEMENTS
The author wishes to express his sincere gratitude to:
Dr K.C. Lam, for his understanding, constant encouragement, constructive criticisms and painstaking correction of the manuscript
in his role as supervisor
Drs S.W. Tam and S.I. Hsu, for their encouragement, guidance
and constructive comments in their role as co-supervisors
- Miss Hilda Kwong of the Royal observatory, for providing
the rainfall data
Mr H.K. Cheung of the Census and Statistics Department, for
the provision of the population data
Messrs T.C. Chau and H.C. Choi of the Agriculture Fisheries
Department, for providing the pig and poultry statistics
- Messrs L.W. Cheng, Y.L. Woo, Y.H. Lau, C.K. Wan, T.T. Law,
K.S. Chan and Misses C.M. Yan, P.L. Chow, S.M. Leung, T.Y. Chan, Y.M. Chan,
Y.W. Au-Yeung, M.H. Cheung, W.M. Too, for their assistance in field work
- Messrs K.P. Tam and M.H. Chan, for collecting the daily water
samples
Mr Kelvin Lee of the Chinese University of Hong Kong, for his
assistance in the laboratory work
- Mr A.C. Liu, for his valuable advice and assistance in computer
work
all those friends who support me with their continuous encourage-
ment throughout the whole research and particularly to
my best friend, Estella, and my family, for their many encouraging
words and sharing with me the ups and downs during these four years. CONTENTS
Page
ABSTRACT iii
ACKNOWLEDGEMENTS v
LIST OF FIGURES ix
LIST OF TABLES xi
LIST OF PHOTOS xiv
CHAPTER
1 INTRODUCTION 1.1 Objectives of the Study 1 1.2 Background of the Study 1 1.3 Literature Review 7
2 DESCRIPTION OF THE STUDY AREA 2.1 Selection of Study Area 10 2.2 Location 10 2.3 Topography 11 2.4 Geology 11 2.5 Climate 15 2.6 Land Use 17
3 STUDY METHOD 3.1 Sampling of Wells 19 3.1.1 collection of gloundwaten samples 20 3.1.2 Collection of pelception Data 20 3.2 Experimental Methods for the Determination of Physical and Chemical Parameters 23 3.2.1 Field Deteimination of Ail and waten Tempelatule and the Depth of water Level Brom giound sunbace 24 3.2.2 Detenmination of PH, Conductivity and NO3-N 24 3.2.3 Detemination of Alralinity 25 3.2.4 Detemination of suspended solid Concentation 25 3.2.5 Detemination of po-and NH4-N 25 3.2.6 Detemination of cl and so4 26 3.2.7 Detemination of silica 26 7
3.2.8 Detemination of Na and K 26 3.2.9 Determination of ca,Mg and other Metal Tons 26 3.3 Data Processing 27
4 GROUNDWATER USE IN THE STUDY AREA 4.1 Background of Water Supply in Rural Hong Kong 28 4.2 Uses of Groundwater in Study Area 29 4.3 Socio-economic Background of Respondents 33 4.4 Summary 37
5 CHEMICAL QUALITY OF GROUNDWATER 5.1 Chemical Characteristics of Groundwater in the Fanling-Sheung Shui area 38 5.2 Classification of Groundwater Samples 44 5.2.1 Hydrochemical Facies of the Groundwater 44 5.2.2 Cluster Analysi of Groundwater Samples 50 5.3 Suitability of the Groundwater for Various Uses 57 5.3.1 Drinking purpose 58 5.3.2 Inrrigation purpose 62 5.3.3 Livestock Puduction 63 5.3.4 Industrial purpose 63
5.3.5 Summary 66 5.4 Spatial Variation of Groundwater Quality in the Study Area 66 5.4.1 Spatial pattern of water Quality Groups 66 5.4.2 Human Factors abbecting the chemical Quality of Groundwater 68
5.5 Temporal Changes in Groundwater Quality 73 5.5.1 S ears o nat V L e,&e.nce/s in Gnoundu,ta ten QuaV ty 73 5.5.2 Day-to-day Changes in Gnoundwater Quality 75 5.6 Summary 83
6 PERCEPTION OF GROUNDWATER QUALITY BY THE WELL USERS 6.1 Well Users' Concern of Groundwater Pollution 85 6.2 Perception of Groundwater Quality by the Well Users 92 6.2.1 CompaitL on o6 the PeAceived Vegtee o6 Cteanliness between Groundwater,Tap waken.and Stream waters 92 6.2.2 Well users'Perceived Cleanliness of Groundwatec of their own wells 99 6.2.3 Indicators Used to identiby Groundwater Pollution by the well useus 102 6.2.4 Discrepancy between Actual and perceived 104 Groundwater Quality 6.3 Adaptative Behaviour towards Groundwater Pollution 109 6.4 Discussion of Results 112 8
7 SUMMARY AND CONCLUSION 7.1 Introduction 113 7.2 Summary of Findings 113 7.3 Discussion of the Findings 115
BIBLIOGRAPHY 117 9
LIST OF FIGURE
Figure Page
1.1 Location of the study area 4
2.1 Topographic map of the study area 12
2.2 Geological map of the study area 13
2.3 Monthly normals of air temperature and total rainfall (from 1947 to 1976) 16
3.1 Locations of sampling points, monitoring stations and rainfall stations 22
4.1 Cumulative frequency distribution of length of time the respondents have lived in their present dwellings 34
4.2 Cumulative frequency distribution of length of time the
respondents have used groundwater 34
4.3 Respondents' education level 35
4.4 Cumulative frequency distribution of the respondents' age 36
4.5 Cumulative frequency distribution of the respondents' total monthly income 36
5.1 Classification diagrams for water types and hydrochemical
facies in terms of major-ion percentages 45
5.2 Groupings of water types and hydrochemical facies of the wet-season groundwater samples 47
5.3 Groupings of water types and hydrochemical facies of the dry-season groundwater samples 48
5.4 Stability field diagrams for aluminium silicates-aqueous solution showing groundwater composition (wet-season) 52
5.5 Stability field diagrams for aluminium silicates-aqueous solution showing groundwater composition (dry-season) 53
5.6 Spatial distribution of the water quality groups (wet-season cases) 69
5.7 Daily fluctuation of rainfall, depth of water level from ground surface (GDEPTH) and concentrations of NO3-N of
the three monitoring stations 76 10
5.8 Daily fluctuation of rainfall, depth of water level from ground surface (GDEPTH) and pH of the three monitoring stations 79
5.9 Daily fluctuation of rainfall, depth of water level from ground surface (GDEPTH) and conductivity of the three monitorinq stations 80
5.10 Monthly means of rainfall, conductivity, NO3-N and pH of three monitoring stations 81
6.1 Conceptual model for the perception study of water
pollution 86
6.2 Frequency distribution of the concern index 89
6.3 Frequency distribution of the pollution index 89
6.4 Categories of discrepancy between the actual and perceived groundwater quality 105 6
LIST OF TABLES
Table Page
1.1 Water demand in Hong Kong 3
2.1 Chemical composition of Repulse Bay Volcanics and its wPathPrPH nrnrlturt=c 14
2.2 Land use of study area (1978) 18
3.1 List of villages where samples were taken 21
4.1 Results of application for metered water supply 30
4.2 Uses of groundwater 31
5.1 Wet-season groundwater quality- summary statistics 39
5.2 Dry-season groundwater quality- summary statistics 40
5.3 Correlation matrix of chemical parameters of wet-season groundwater samples 42
5.4 Correlation matrix of chemical parameters of dry-season groundwater samples 43
5.5 Classification of water types and hydrochemical facies 49
5.6 Weathering reactions of the major fine welded tuff forming minerals 51
5.7 Relative contribution each water quality parameters to each discriminant function (wet-season samples) cc
5.8 Chemical characteristics of the cluster groups (wet-season samples) CF
5.9 International standards for drinkinq water 59
5.10 Comparison between the chemical quality of groundwater and the drinking water standards set by the World Health Organization (1971) 60
5.11 Effects caused by the excessive amounts of inorganic
constituents in groundwater 61
5.12 Comparison between the chemical quality of groundwater and the irrigation water standards 64 7
5.13 Recommended concentration limits for water used for
livestock production 65
5.14 Water quality standards for industrial use 67
5.15 Pearson's r between four chemical parameters and the human factors (dry-season cases at the well level 71
5.16 Pearson's r between four chemical parameters and the human factors (wet-season cases at the village level 71
5.17 Pearson's r between four chemical parameters and the human factors (dry-season cases at the village level 71
5.18 Partial correlation between COND and POP (wet-season cases at the village level) 72
5.19 Partial correlation between COND and POP (dry-season cases at the villae level) 72
5.20 Results of paired t-test of wet-season and dry-season groundwater Quality 74
5.21 Pearson's r between API, GDEPTH and chemical quality data collected at the three monitoring stations 82
6.1 Calculation of concern index 88
6.2 Measurement scales for variables in the analysis 91
6.3 Coefficients of contingency and Kendall's tau c for measuring the relationship between level of concern and some socio-economic and environmental factors 93
6.4 Cross-tabulation of level of concern by sex 94
6.5 Cross-tabulation of level of concern by smell 94
6.6 Respondents' ranking of cleanliness among three types. of water sources 96
6.7 Number of respondents who perceive that water source i is cleaner than water source i 96
6.8 Percentage of respondents who perceive that water source i
is cleaner that water source j 96
6.9 Coefficients of contingency for measuring the relationship between users' perceived cleanliness of three water sources and some socio-economic and environmental factors 97
6.10 Cross-tabulation of ranking of cleanliness by "education level" 98 8
6.11 Respondents' perceived quality of the groundwater they use 98
6.12 Coefficients of contingency and Kendall's tau c for
measuring the relationship between users' perceived cleanliness of the groundwater they use and some quality and socio-economic factors 100
6.13 Cross-tabulation of respondents' perceived cleanliness
of the groundwater they use by three sensible quality parameters- smell, "colour" & turbidity and
whether or not the respondent uses groundwater for drinking purpose 101
6.14 Indicators commonly used by respondents for evaluating the groundwater quality 103
6.15 Frequency distribution of the three categories of
discrepancy between actual and perceived groundwater quality 103
6.16 Coefficients of contingency and Kendall's tau c for measuring the relationship between categories of discrepancy and some socio-economic and environmental factors 106
6.17 Cross-tabulation of categories of discrepancy by
farmer, whether or not the respondent uses ground- water for drinking purpose and education level 107
6.18 Cross-tabulation of categories of discrepancy by
level of concern of groundwater pollution 108
6.19 Calculation of action index 110
6.20 Cross-tabulation of level of action by level of concern of groundwater pollution and respondents'
perceived cleanliness of the groundwater they use 111 14
LIST OF PHOTOS
Photo Page
4.1 A typical example of the wells in the study area 32
5.1 "Cement-rings" used for construction of the inner wall of the well 77 1
CHAPTER 1
INTRODUCTION
1.1 Objectives of the Study
This thesis is based on a study or the chemical quality or groundwater in the Fanling-Sheung Shui area and the perception of its quality by the well users. The objectives of the study were to:
a) investigate the chemical quality of groundwater and its spatial
and temporal variations
b) study the well users' perception of the quality of groundwater
and
c) examine the discrepancy between the actual quality of ground-
water and the quality as perceived by the users.
L.2 Background of the Study
Groundwater is an important'source of water supply throughout
the world particularly in those areas where surface water is lacking
Dr scarce. Its utilization dates back the earliest time.
In Hong Kong, the two major factors leading to the water scar-
city problem are land and population. There are no sizeable lakes or
rivers within the territory of Hong Kong and most of the land area
(1,055 km2) is spread over 236 islands and islets, therefore giving no
sizeable land for the construction Of reservoirs. What the people can
rely on is an erratic rainfall supply and the water must be impounded
by the existing 17 reservoirs which are fed mainly by artificial catch-
waters. With the completion of the High Island Reservoir in 1978, Hong 2
Kong's storage capacity has increased to 579 million cubic metres
(Water Supplies Department, 1981) but it is still barely sufficient to meet the needs of the five million inhabitants. Such situation is further complicated by the fact that water received during the six wet months have to supply the population for the rest of the year.
Additional fresh water can be obtained from China and by the costly
desalination method. Although the supply from China increases pro- gressively from 22.7 million cubic metres in 1960 to 182 million cubic metres in 1982 (Water Supplies Department, 1981), we are still cons-
tantly threatened by the shortage of fresh water because of the rapidly
increasing water demand (Table 1.1).
The water problem is especially serious in the rural New
Territories of Hong Kong. With the development of the rural area,
the major towns and villages in the New Territories are now provided with piped potable water supplies and the distribution network is con-
tinually being extended. Although potable water is supplied to about
73% of the rural population (Binnie Partners, 1974), many remote
villages still have no potable water supply and the inhabitants have
to depend on groundwater as the major or even the only source of water.
Groundwater has thus to be used for drinking, domestic, irrigation,
stock feeding, industrial and other purposes. Even in those regions
where the tap water is available, some people still prefer to use
groundwater. In fact, gradually expanding tap water distribution net-
work has not reduced the demand for groundwater in the New Territories,
and contrary to popular belief, the number of wells is increasing
(Chan, 1977). According to a pilot 'study conducted by the author
in the Fanling-Sheung Shui area (Figure 1.1), it was found that the
utilization of groundwater was very popular. In spite of its small
percentage of contribution to the total water supply for the rural 3
TABLE 1.1
WATER DEMAND IN HONG KONG
Mean Daily Demand Daily Per Capita Consumption Year (in thousand cubic metres) (in cubic metres)
1960 281 0.09
1962 331 0.10
1964 327 0.09
1966 555 0.15
1968 619 0.16
1970 759 0.19
1972 889 0.22
1974 957 0.22
1976 1107 0.25
1978 1130 0.24
1980 1390 0.27
1982 1420 0.27
SOURCES: The Family. Planning Association of Hong Kong (1977)
Water Supplies Department (1981) and
Hong Kong Government Information Services (1982). N CHINA
R Indus
Sheung Shui R Fanling Plover Cove Beas Reservoer
Ping Yuen Tai Po Shan Long Kam Tin
Chinese University
NEW TBRRITORIES
High lsland Reservoir
KOWLOON
LEGEND: HONG KONG ISLAND LANTAU ISLAND Rive Study Area Political Boundary
CHINA
0 1 2 3 4 Km H.K. 4
FIGURE 1.1 LOCATION OF THE STUDY AREA 5
Population in the New Territories, groundwater is still a very import-
ant local water source.
Although the quality of groundwater is generally better than surface water in many countries, this may not be the case in Hong Kong.
Due to the recent rapid urban development and population increase in
the New Territories, it is not unlikely that groundwater in the New
Territories has been contaminated and has become unsafe for human con-
sumption. The insufficient and inadequate provisions for solid wastes
and sewage disposal further aggravate the problem. A great portion of
sewage is directly discharged into the nearby natural waterways. More-
over, refuse dumps of various sizes can be found in a great number of
locations in the New Territories (Binnie Partners, 1974). Refuse
disposed of in such way will cause serious leaching of pollutants down-
wards with rainwater.
Agriculture is another major human activity which may influence
groundwater quality. The main agricultural activities that can cause
degradation of groundwater quality are the usage of chemical fertilizers,
pesticides and the storage or disposal of livestock or fowl wastes on
land (Singh and Sekhon, 1976 1978). In Hong Kong, the disposal of
livestock wastes is believed to be the most important factor contributed
to the groundwater pollution.
According to the findings of a pilot study carried out by the
author in April of 1980, the NO3-N content of 9 out of 24 groundwater
samples taken in the River Beas Valley (Figure 1.1) exceeded 10 mg/l,
the upper safety limit for drinking purpose set by the World Health
Organization (1971). Such findings seem to suggest that pollution of
groundwater can be serious in this region.
Some water pollutants, if present in excessive amounts, may
give rise to a lot of domestic troubles such as excessive scale formation, 6
corrosion of pipes, unpleasant taste and discoloration of laundry and some may even have chronic hazardous effects on human health. For example, high NO -N content in drinking water will cause methaemoglo- 3 binaemia in infants (Wild, 1977 Hui Mao, 1979). Even in adults,
nitrates may be having an effect on the cardiac function and it has
also been found that there is a possible relationship between the high
nitrate levels in potable water supplies and the earlier onset of
hypertension (Malberg et al., 1978). Moreover, nitrates can react
with amines to form the N-nitroso compounds which have been shown in
animal experiments to be among the most potent chemical carcinogens
known to date (Griciute, 1978).
There is also evidence to show that the groundwater in the New
Territories is bacteriological contaminated. An earlier survey under-
taken by Mark and his associates showed that water samples collected
from 14 wells in Yuen Long contained an average of 3,200 Escherichia coli
per 100 ml (quoted in Lam, 1981a), indicating that the water was faecally
polluted. Groundwater high in coliform bacteria is an indication of
domestic sewage contamination.
Whilst biological pollutants such as pathogenic bacteria and
virus can be rendered harmless simply by boiling, some chemical pollutants
such as NO3-N and heavy metals, are more difficult to be dealt with.
The health effects of such chemical pollutants have only been recognized
recently. The problem of groundwater pollution has seldomly been dis-
cussed in the newspaper and most of the well users are not aware of this
problem. Some of them even insist that the water they drink is abso-
lutely clean. If they do have such perception and also if the water
they drink is in actual fact polluted, then there exists very serious
health risks because they have no incentive to look for other water
sources or even ignore the pretreatment measures such as precipitation 7
and boiling. Therefore, a detailed and comprehensive investigation of
the groundwater quality, and local inhabitants' perception of the pro- blem becomes urgent and significant.
1.3 Literature Review
The quality of groundwater is determined by a wide range of
Factors, among which rock type and topography are the more important
Dnes. It has been suggested that the chemical quality of the ground-
water is controlled by the mineralogical and chemical composition of
the rocks and soils through which the water percolates (Eriksson
Khunakasem, 1966 Brown, 1972). The topography determines the direction
Df movement of groundwater which in turn affects the dilution or con-
--entration of pollutants in the aquifer (DeWiest, 1965 LeGrand, 1972).
Contamination of groundwater is caused mainly by anthropogenic
activities. High levels of nitrogen and phosphorus are mainly derived
from chemical fertilizers (Singh Sekhon, 1976 1978), and wastes of
animal and poultry (Mielke Ellis, 1976 Ciravolo et al., 1979 and
Solt et al., 1979). Nitrogen compounds-in fertilizers are largely in
forms of ammonium sulphate, anhydrous ammonia, ammonium nitrate, sodium
nitrate, calcium nitrate and various ammoniated phosphates and super-
phosphates. These compounds are highly soluble and can be carried by
the percolating water to the aquifer below when precipitation or irri-
gation periodically exceeds plant requirements (Feth, 1966). Seepage
from septic tanks, sewage ponds or pipelines, and leaching from refuse
dumps also contributes a great amount of pollutants, especially nitrates
and phosphates, to the groundwater (Viraraghavan Warnock, 1976 Lance,
1977). Industrial activities such as metal processing, dyeing, electro-
plating and leather processing are the main sources of heavy metals in
groundwater (Walton, 1970). 8
Contrary to the study of groundwater chemistry, not many studies have been undertaken to study the people's perception of the groundwater pollution problem. Therefore, the amount of literature on the perception aspects of groundwater pollution is very limited. However, some methodo-
logical considerations in the measurement and analysis of people's per- ception of water quality have been dealt with by Jacoby (1972) and
Coughlin (1976). Jacoby's study focused on investigating the citizens' attitudes toward air, noise and water pollution in Detroit, and the circumstances under which people are concerned about the condition of their physical environment. It was found that there is a statistically significant positive relationship between concern about environmental quality and the length and intensity of exposure to noxious stimuli.
The lower the level of environmental quality to which a person is ex- posed, the greater is his level of concern. The research also suggested
that such perception is largely independent of various socio-economic
characteristics of the population. Coughlin's research emphasized on
the methodological issues in studying the perception of water quality.
Besides, a recent study concerned with people's perception of
water quality was conducted by Akintola et al. (1980) in the rural areas
of Nigeria. It was found that most of the rural people held a largely
misleading perception that water which looked clean would not render one
sick. Their evaluation of cleanliness of the water source was heavily
depended on the taste and visible characteristics of the water body.
It is clear from the above review that most of the groundwater
studies are concerned with the chemical and physical properties of the
water, with very little regard to how the users perceive and use the
water. Since very little attention has been paid to the perception as-
pects of groundwater quality, this thesis emphasizes both the perceptual
and chemical aspects of qroundwater quality, and attempts to find out 9 how the discrepancy between the actual and perceived quality can affect
the behaviour of the users. 10
CHAPTER 2
DESCRIPTION OF THE STUDY AREA
2.1 Selection of Study-Area
-rnis study was carriea out in the ranging-5neung 5nui plain drained by the River Indus (Ng Tung Ho) system. It was chosen because:
a) A pilot study previously carried out by the author in one of
the tributaries of River Indus indicated that groundwater in
the area was contaminated and also that groundwater was the
main source of water in the region. Since most of the well
users were not aware of the existence of pollution and the
consequence of drinking polluted water, there is an urgent
need to extend the scope of the study to cover the whole
drainage basin of River Indus.
b) The River Indus drainage basin is near to the Chinese University
campus and can be reached by a number of transportation means.
Water samples can thus be transported back to the laboratory
within one or two hours after collection.
c) Human activities in the study area are conductive to groundwater
pollution. The dominant types of human activities in this region
are vegetable and flower cultivation, pig rearing and poultry
breeding. It is widely known that such agricultural activities
can lead to groundwater contamination.
2.2 Location
The study area covered the whole drainage basin of River Indus 11
and all its tributaries. It is located in the Fanling-Sheung Shui
plain (22°27'N- 22032'N 114°06'E- 114012'E) of the northern part
of the New Territories of Hong Kong (Figures 1.1 2.1). The total
area is 58 km2. Within the drainage basin are two major market towns
(Shek Wu Hui and Luen Wo Hui) and 124 villages of various sizes.
2.3 Topography
Fanling-Sheung Shui plain is a historical flood plain of the
River Indus system, and very little topographic relief is evident
within the area. The area is surrounded by a series of hills with
altitudes ranging from 400 to 600 metres (Figure 2.1). Most of the
land below 100 metres are used for cultivation and are also the area
where wells are commonly found.
The plain is interlaced with small channels which serve the dual
purpose of irrigation of agricultural land and drainage of runoff from
the area. Drainage in the study area is made up of five major streams:
River Indus (Ng Tung Ho) on the northern part of the area and River
Beas (Sheung Yue Ho), River Sutlej (Shek Sheung Ho), River Chenab (Kwan
Tei Ho) and River Jhelum (Tan Shan Ho) on the south (Figure 2.1).
2.4 Geology
With the exception of a line of low hills along the northern
margin which are made up of metamorphosed sedimentary and volcanic
rocks (Figure 2.2), most of the hills surrounding the study area are
underlain dominantly by pyroclastic rocks (fine welded tuff) with some
lavas. Some coarse tuff is also found in the south-western part.
The welded tuff is easily weathered to form a clayey silt
abundant in kaolinite (Lumb, 1975). Table 2.1 shows that there is an
increase in the proportion of A10 and Fe03 and a loss of Si0, Na, N 400 CHINA 300 200 100
River Chum Man UK Pin
Loi 100 Wa Shan Tung
Ma Mei Leng Ha Shum Hung Tsai Leng R. 100 Jheium 200 Shok Wu Fung Hui Ho Sheung Siu Ko Po 300 Kong 400 Tung Heung Indus Hang kwan Tei Fong R. Kwu Tung Ma Shi R R. Luen Wo Hui Wing Ning Tsuen Chenab
Hang Tau
Pak 100 Tong Kung Lung 200 Leng Fuk Hok Tau Tsuen 300 Wai 400 Sutlej R. 300 R. Lin Tong Tin Sam Mei R. Wo Hop 200 CheungLet Boas 100 She
100 Tsiu Tai Lung Farm Keng Ying Pun
100 LEGEND: 200 500 Ta 100 300 Shek contour 400 400 300 Wu 200100 railway
main road
settlement
river 0 1 2 km boundary of study area rainfall 100 station
12 FIGURE 2.1 TOPOGRAPHIC MAP OF THE STUDY AREA LEGEND: Dominantly pyoclastic rock with some lavas (RBp)
Colluvium undifferentiared
Raised alluvium
Alluvium undfferentiated 0 1 2 km metamorphosed sedimentary and volcanic rocks (LMC)
Coarse tuff (RBc)
lnternadded congomerate, pebbly sandstone and cleaved mudston (Pl)
FIGURE 2.2 GEOLOGICAL MAP OF THE STUDY AREA (After Liu 1981) 13 14
TABLE 2.1
CHEMICAL COMPOSITION OF *REPULSE BAY VOLCANICS
AND ITS WEATHERED PRODUCTS
Fresh(%) Advanced Weathering(%)
Si02 75.70 73.19
A1203 13.04 17.51
Fe203 0.11 0.82
FeO 1.30 0.53
MgO 0.22 0.31
CaO 0.76 0.05
3.37 Na 20
K 0 4.78 3.54 2
H2O 0.46 3.98
0.05 0.07 H 2O
0.10 co 2
TiO 0.15
Total 100.04 100.00
SOURCE: Davis, S.G. (1953)
Equivalent to Repulse Bay Welded Tuff (RBp) as mapped by Allen Stephens(1971). 15
Ca and K ions during the process of chemical weathering of welded tuff.
The result of this process is the accumulation of hydroxides of alumini
and iron in the upper zones of the soil profile and the leaching of
silica as well as alkali and alkaline ions. The relative mobility
sequence found by Liu (1981) suggests that Na and Ca are the two most
mobile elements in the process of weathering of welded tuff, and the
Al the least. Therefore, the uncontaminated groundwater and stream
water of the study area should have Na, Ca and SiO 2 as their major
constituents.
In the lower part of the drainage basin, alluvial deposits of
considerable depth overlay decomposed residual material. It is within
these alluvial deposits that shallow groundwater is found. The parent
rocks producing the alluvial deposits are various, both volcanics and
metamorphosed sedimentary rocks have been identified.
2.5 Climate
Hong Kong has a tropical monsoon type of climate, with cold and
dry north-easterly winds blowing from the land to the sea in the winter
months (October to mid-March) and hot and wet south-easterly winds in
the summer months (mid-April to September). The monthly normals of
temperature and rainfall are shown in Figure 2.3.
The mean monthly temperature of Hong Kong ranges from 160C in
January to 28 in July. The average annual temperature range indicates
the modifying influence of the sea.
Hong Kong receives an average annual rainfall of 2,246 mm but
it varies a great deal from year to year. From Figure 2.3, it can be
seen that over 80% of the total rainfall fall in the five months of May
to September. Of the other seven months, none is completely dry. The
year of sampling was not particularly dry. The annual rainfall recorded 16
FIGURE 2.3
MONTHLY NORMALS OF AIR TEMPERATURE AND TOTAL RAINFALL
(FROM 1947 TO 1976)
30 600 TEMPERATURE
Rainfall 560
520 T 25 e m 480 p e 440 r R a 20 400 a t u i 360 r n e f 320 a
15 l (0C) l 280
240 (nm)
10 200
160
120
5
80
40
0 0
J F M A M J JA S O N D
SOURCE: Hong Kong Royal Observatory. 17
at the two rainfall stations, Fanling Army Depot and Tai Lung Farm
(Figure 2.1), in the study area was 2,208 mm and 2,049 mm respectively.
The high temperature and abundant rainfall in summer months favour the chemical weathering of rocks and enhance the release of
solutes to the stream water and groundwater.
2.6 Land Use
In spite of the rapid rate of urban development of-the rural
New Territories in recent years, the lowland portion of the study area
is still dominated by agricultural activities including vegetable and
flower cultivation, pig rearing, poultry breeding, game-fish culture
and small-scale market gardening. Commercial activities are mainly
concentrated at the two major market towns (Shek Wu Hui and Luen Wo Hui)
and some larger settlements such as Ma Mei Ha, Kwan Tei and Wo Hop Shek,
where shops providing low-class functions are scattered along the main
roads (Figure 2.1). Some small-scale industries, such as dyeing, metal
works, food-manufacturing, rattan cleaning, electro-plating and saw mills
are found at Hung Leng, Kwan Tei North and Yin Kong areas.
The percentage of different types of land use in the study area
was estimated by Liu (1981) based on the data provided by the Lands
Survey Department and the Agriculture Fisheries Department (Table 2.2).
It was found that more than 50% of the land of the Indus Basin, parti-
cularly in the upper course of the river, is grassland and woodland. In
the lower part of the basin, the proportion of grassland and woodland
diminishes, and the major part of the area is made up of cultivated land,
fallow land, built-up area and fish ponds. 18
TABLE 2.2
LAND USE OF STUDY AREA (1978)
Land Use Total Area (Km4) Percentage
Grassland and woodland 30.3 52.3
Fallow land 2.9 5.0
Cultivated land 10.0 17.2
Built-up area 13.8 23.8
River channels and ponds 1.0 1.7
Total 58.0 100.0
SOURCES: Lands Survey Department and
Agriculture Fisheries Department. 19
CHAPTER 3
STUDY METHOD
Since this study aims at studying the chemical quality of groundwater and the perception of its quality by the users, ground- water samples had to be collected for analysis and users of ground- water had to be interviewed. Thus, the well, together with its content
(i.e. water) and user, became the basic unit of study.
3.1 Sampling of Wells
As'this study attempts to estimate the overall chemical quality
of groundwater in the study area and to depict any regional variation
pattern, the sampling method must be practical and statistically sound.
The systematic random sampling method (Dixon Leach, 1977)
is one of the more favoured spatial sampling methods. To use this
method, the locations of all sampling units (i.e. wells) have to be
known. However, the locations of wells in the study area are not known.
Even the relevant government departments such as the Agriculture
Fisheries Department, Public Works Department and Tai Po Northern Dis-
trict Office do not have such data. Therefore, the systematic random
sampling method has not been followed and a modified method has been
adopted. Instead of selecting samples randomly as required in the
systematic random sampling method, a meet-and-take approach has
been used in this study. The drainage basin was divided into grids
measuring 1 km X 1 km using the co-ordinates on the 1:20,000 topographical
mans (Series HM20C) and a quota of 10 samples is assigned to each grid. 20
Following the method, a total of 215 wells from 75 villages
(Table 3.1) were selected. The location of the sampling points are shown in Figure 3.1. Groundwater samples were collected twice from each selected well, one in the wet season and the other in the dry season. Sampling of well water in wet season started originally in
July 3, 1980, but was twice interrupted by heavy rainfall. To avoid any marked effect of rainfall on groundwater quality, sampling was carried out during the period from August 2 to August 5, 1980. No
rainfall was recorded during the sampling period or three days prior
to sampling. The samples of dry season were collected from December 29,
1980 to January 4, 1981. No rainfall was recorded for a whole month
before sampling.
Apart from the two large scale sampling carried out in the wet
and dry seasons, three wells were selected as monitoring stations
where water samples and readings of depth of the water level from
ground surface were taken daily for studying the day-to-day fluctuation
of chemical quality. Water samples were collected from the two stations
at Pak Fuk Tsuen from July 1 to December 31, 1980 and the third one at
Ta Shek Wu from July 1 to September, 1980 (Figure 3.1).
3.1.1 Cottection of Gnounvaten Samptes
Polythylene bottles were used for collection of water samples.
The bottle was rinsed with the water to be sampled before each collection.
It was completely filled and was free from floating debris or scum so
that changes in water quality could be minimized.
3.1.2 Cottection of PeAception Data
The data concerning well users' awareness of the groundwater
pollution problem and their estimation of the degree of cleanliness of
groundwater were obtained by face-to-face interview with the users whose TABLE 3.1
LIST OF VOLLAGES WHERESAMPLES WERE TAKEN
No. of Samples No, of No, of Samples No, of Collected Questionnaires Village Collected Questionnaires Collected Village Collected Wet-season Dry-season Wet-season Dry-season 6 6 1 1 *Man Uk Pin San Tsuen 6 *Man Uk Pin 1 10 3 1 Loi Tung Tsuen Wast 6 11 Loi Tung Tsuen 3 2 2 1 Loi Tung Tsuen North 9 8 7 *Tai Tong Wu 3 3 6 3 3 Wang Shan Keuk Tsuen 3 Leng Tsai 2 1 6 7 5 Hung Leng Tsuen South 1 Hung Leng Tsuen East 5 5 4 4 Hung Leng Tsuen North 4 5 Hung Leng Tsuen West 1 1 1 1 1 *Leng Pei Tsuen 1 Ma Mei Ha 1 1 1 1 2 1 *Hok Tau Wai *Hok Tau Tsui 1 1 4 *Ho pa 1 *Kan Tau Tsuen 3 4 1 0 San Tong Po 2 2 1 Ko Po 1 1 1 6 7 5 Kwan Tei Tsuen 1 *Ko Po Tsuen North 2 2 3 3 3 Fu Tei Pai Tsuen 2 Kwan Tei Tsuen North 1 1 1 Kwan Tei Tsuen West 2 1 1 Ma Liu Shui San Tsuen 4 4 Tung Kok Wai 1 1 1 Wing Ning Tsuen 4 1 1 1 1 Wing Kong Shan 1 Tsz Tong Tsuen 1 3 3 San Wai 3 3 3 Siu Hang Tsuen 3 4 7 6 6 Siu Hnag San Tsuen 4 4 Ma Shi Po 6 4 4 Fanilng Tsuen 1 1 Sheung Shui Tsoi Yuen Tsuen Tin Ping Shan Tsuen 1 6 Ha Pei Tsuen 2 2 2 1 Fu Tei Au 4 4 3 Hung Kiu San Tsuen 1 1 2 3 * Wa Shan 1 1 1 *Ho Pui Tsuen 2 1 1 1 Yin Kong 1 1 1 *Tin Kwong Po 7 7 6 Shek Wu San Tsuen 6 3 6 Pak Fuk Tsuen 2 4 Kai Leng 2 2 2 Ping Kong San Tsuen 2 4 4 3 *Ho Sheung Heung San Tsuen 2 2 2 *Ho Sheung Heung 4 *Fung Kong 6 6 6 Tung Fong Tsuen 3 4 1 0 Kam Tsin 2 0 0 Tsung Pak Long 1 Tong Kung Leng 4 3 3 Hang Tau Mei Tsuen 1 1 1 3 2 Hang Tau 2 3 3 * Cheng Lek 6 Lin Tong Mei 3 3 2 Tin Sam Tsui Tsuen 2 2 1 1 1 Ki Lun Tsuen 2 2 2 Tsiu Keng 3 Tsiu Keng Lo Wai 3 3 3 *Tsiu Keng Pang Uk 2 2 2 3 3 *Lung Shan Tsuen 2 2 1 *Tai Lung Hang Tsuen 3 *Sheung On Po 1 1 1 Tin Sam Tsuen 2 0 0 0 Wo Hop Shek Tsoi Yuen Tsuen 2 0 0 Tong Hang Tsuen 1 0 *Ta Shek Wu 7 6 7 Ying Pun 5 5 5 *San Uk Tsai 0 1 1 Ran Chuk Hang Lo Wai 0 1 0 Kwu Tung 1 1 1 #*Tung Shan Ha 0 0 0 0 0 0 #* Kwai Tau Leng 0 0 0 #Rai Tau Leng # Nagu Tei 0 0 0 # Tan Chuk Hang 0 0 0 #Lau Shui Heung 0 0 0
Ttal 117 111 100 Total 98 95 87
*Village without metered water supply and standpipes Village with pubilc standpipes #Village investigated but no well users were found. 21 R. Indus
R. Sutlei
R. Chenab R. Beas R.Jhelun
R. Lung
FIGURE 3.1 LOCAIONS OF SAMPLING POINTS. MONITORIN
STATIONS AND RAINFALL STATIONS □ sampilng points
▲ monitoring stations
★ rainfall stations 22 23
wells were selected for water sampling.
The questionnaire consists of four parts. The first and
second parts were designed for the users and non-users of well water
for drinking purpose respectively, dealing with their reasons for using
groundwater and the uses of groundwater. The third part was used to
obtain personal information of the respondents and the last dealt with
other relevant data such as the type of nearby land use, the condition
of the well and the occurrence or otherwise of pollution sources.
Questions of the questionnaire were set in Chinese so that most of the
respondents can understand.
3.2 Experimental Methods for the Measurement of Physical and Chemical
Parameters
Owing to the lack of equipment for microbiological and organic
analyses, this study focusses only on the inorganic constituents and
physical properties of the groundwater. The following parameters were
measured: water temperature, pH, conductivity, alkalinity, chloride,
sulphate, phosphate-phosphorus, nitrate-nitrogen, ammonium-nitrogen,
silica, suspended solids (for wet season only), potassium, sodium,
calcium, magnesium, zinc, lead, iron, manganese, nickel, cadmium, copper
and chromium. Dissolved oxygen was not measured because nearly all
samples were collected through pumping which renders the readings un-
reliable.
Apart from the above parameters, air temperature and the depth
of the water level from ground surface were measured at the time of
sampling. All water samples returned to the laboratory were kept under
dark in the refrigerator to minimize chemical and biological changes.
Effects of sample storage on the analytical results were not assessed
and were assumed to be minimal. 24
Ideally, all samples should be analysed immediately after col- lection, but it was impossible to do so because of time and manpower constraints. Conductivity, pH and NO3-N were determined on the same day of collection. Alkalinity was measured within three days and was followed by filtration for the measurement of suspended solids. PO 4 -P
and NH4-N were detected within two weeks, Cl, SO4, silica and metal
ions (Na, K, Ca, Mg, Zn, Pb, Fe, Mn, Ni, Cd, Cr and Cu) were determined within two months.
3.2.1 Fietd vetenmination of Ain and Water Tempenature and the Depth
of water levet from Gnound Surface
An alcohol thermometer was used tor the measurement or air
temperature and temperature of the water samples. It was left in the
sample for more than three minutes before any reading was taken. The
depth of water level from ground surface was determined by a graded
rope with a bucket at the end. When it was not possible to take direct
measurement, it was then only estimated visually.
3.2.2 Determination of pH, Conductivity and NO3-N
These three parameters were'determined on the same day of
sampling. pH was measured on a Radiometer pHM29 pH Meter which is
temperature adjustable while conductivity measurement was made on a
Radiometer CDM2 Conductivity Meter and was adjusted to the reference
temperature of 25°C.
NO3-N was measured by the Ultraviolet Spectrophotometric
Method (Tentative) (American Public Health Association, 1971). Quartz
cells were used and were tested and matched before measurement. Absorb-
ance was measured on a SHIMADZU Spectrophotometer at a wave-length of
220 n, for nitrate reading and also at 275 T to obtain the interference
due to dissolved organic matter. The absorbance due to nitrate was then 25 obtained by subtracting two times the reading at 275 mt from the reading at 220 m.. This absorbance value was converted into equivalent nitrate by reading the nitrate value from a standard calibration curve obtained at 220 mt.
3.2.3 Determination of Alkalinity
Alkalinity was determined by the Conductometric Titration
Method (Lam, 1981b). This method involved the titration of about 100 ml
of sample with 0.01639 N H2SO4 (or 0.08195 N depended on the concentration
of HCO3) in a conductivity cell. The end point was obtained by plotting
the conductance against titrant volume.
1000 Titrant (0.01639 N) Volume from Carbonate to Bicarbonate HCO3-in mg/l = sample Volume in m= End Point
3.2.4 V etetun naLLan o Sws pended SotLd CavicewtAation
Suspended solid concentration was determined by filtration
of about 500 ml of water sample (exact volume was recorded) through
Whatman 542 filter paper. All filter papers were first soaked in dis-
tilled water overnight, dried in the oven, and accurately weighed by
an analytical balance to the nearest milligrams. After filtration,
each filter paper was again dried at 100C overnight and weighed again.
Then the suspended solid concentration in mg/l can be found.
3.2.5 Determination of PO4-P and NH4-N
Phosphate-phosphorus and ammonium-nitrogen were detected
colorimetrically. The Phosphomolybdate Method (Murphy Riley, 1962)
is specific for the orthophosphate form of phosphorus. Orthophosphate
is converted to phosphomolybdate by acidified ammonium molybdate reagent.
When phosphomolybdate is reduced with ascorbic acid in the presence of
antimony, an intense blue complex is developed that absorbs light at 26
882 nU. The Nessler Method (Allen, 1974) is a sensitive method for the
measurement of NH4-N concentration. Nessler reagent reacts with the
NH4-N and forms a brown solution which absorbs light at 410 m/u.
3.2.6 Determination on ce and SO4
Chloride was determined by the Mercurimetric Method (Brown,
et al., 1970). The endpoint was obtained by titrating about 50 ml of
water sample, added with mixed indicator and HNO3, with mercuric nitrate
standard solution until a blue-violet colour persists. Sulphate was
determined by the Barium Chromate Colorimetric Method (Iwasake et al.,
1957).
3.2.7 Determination os Sicica
Silica was determined by the Molybdate Blue Method (Chan,
1965). Metol-sodium sulphite was used as the reducing agent and any
interference due to the presence of phosphate was suppressed by the addition of oxalic acid. Absorbance was then measured at 810 mu. on a
SHIMADZU Spectrophotometer.
3.2.8 Determination os Na and K
Na and K were determined on an EEL Flame Photometer (Mark II)
The flame was left for five minutes to stabilize before taking any read-
ing. The zero and the full-scale deflection were checked and reset fre-
quently throughout the run.
3.2.9 Determination os Ca. Mq and otheta. Metal Ions
All these metal ions were detected on an Instrumentation
Laboratory Model 257 Double Beam Atomic Absorption Spectrophotometer
using air-acetylene flame. 27 3.3 Data Processing
The data obtained in this research were processed by the IBM
3031 computer at the Chinese University of Hong Kong. The SPSS
(Statistical Package for Social Sciences) developed by Nie et al. (1975) has been used for statistical analyses, including descriptive statistics, frequency distribution, cross-tabulation, t-test, correlation analysis and discriminant analysis. The SAS (Statistical Analysis System) derived by Helwig et al. (1979) was used for cluster analysis. 28
CHAPTER 4
C,RC)TINDWATR USE TN THE STUDY AREA
This chapter describes the uses of groundwater in the study
area and the users' socio-economic background. It provides the basic
background information against which results in Chaper 5 and 6 can be
assessed.
4.1 Background of Water Supply in Rural Hong Kong
In Hong Kong, most of the urban areas are provided with metered
potable water supplies except in squatter areas where only standpipes
are provided. Though the major towns and villages in the New Territories
are provided with piped potable water supplies and the distribution net- work is continually being extended, potable water is only supplied to
about 73% of the rural population (Binnie Partners, 1974). The re-
mainder of the inhabitants obtain their-supplies from local wells or
from hillside streams.
The provision of the piped water to rural communities in the
New Territories faces many difficulties. The difficult terrain and the
large number of small and scattered population centres make the ins-
tallation of water supply system costly. The congested and very confused
settlement layout also hinders the laying of pipelines. Furthermore,
the provision of metered water supply or standpipes can never keep up
with the very rapid rate of squattering in the rural areas.
Among the 187 well users interviewed, only 32.6% had metered
water supply as well. The rest depended on the wells (61.0%), public standpipes (2.1%) and nearby streams (4.3%) for drinking water. For
those who are not provided with metered water supply, only 24.6% have
applied for the piped water and results of their application are sum- marized in Table 4.1.
4.2 Uses of Groundwater in Study Area
As this study was not designed to estimate the percentage of
population provided with metered water supply in the New Territories,
the study emphasizes only on the usage of groundwater in the Fanling-
Sheung Shui area. Results of this survey indicated that among 24 of
the 81 villages studied were neither provided with metered water supply
nor standpipes. Two other villages had no metered water supply but
were served by standpipes (Table 3.1 on p.21). The inhabitants of these
24 villages had to depend on other water sources, particularly ground-
water, for their daily consumption. These villages are generally lo-
cated at remote areas or are sparsely populated.
Table 4.2 summarizes the uses of groundwater in the study area.
Over 70% of the respondents use groundwater for drinking purpose. Ground-
water is also commonly used for domestic purposes such as bathing, laun-
dry and other washing purposes. It is clear that well users who are not
using groundwater for drinking purpose still consume it for domestic
uses. Over half of the well users use groundwater as irrigation water
for vegetable cultivation to minimize the production cost. The suit-
ability of groundwater in the study area for different uses will be
discussed in detail in the next chapter.
During the interview, the maintenance and conditions of the wells
were also observed. It was found that most of the wells had been well
maintained. The majority were equipped with pumps and covered by iron-
nets for safety purpose (Photo 4.1). 30
TABLE 4.1
RESULTS OF APPLICATION FOR METERED WATER SUPPLY
Percentage Results
Applicants have not received any reply 25.8
Applications have been refused by the Water Authority for technical reasons such as distance from the 29.0 nearest water main and insufficient number of households to make construction work cost effective.
16.2 Applications were under consideration.
Applicants got the promise of the Water Authority that metered water supply will be provided in the 29.0
coming future. 31
TABLE 4.2
USES OF GROUNDWATER
Uses of Groundwater No. of Cases Frequency(%)
Drinking purpose 137 73.3
Domestic purposes:
For bath 145 77.5
Washing of clothes 156 83.4
Other washing purposes 153 81.8
Flushing 1 0.5
Agricultural purposes:
Vegetable cultivation 99 52.9
Flower cultivation 7 3.7
Breeding of pigs 40 21.4
Breeding of chickens 35 18.7
Breeding of ducks 5 2.7
1.6 Breeding of pigeons 3
Culturing of edible fishes 1 0.5
Culturing of game fishes 4 2.1
2.7 Industrial purposes 5
Total no. of cases= 187 32
PHOTO 4.1
A TYPICAL EXAMPLE OF THE WELLS IN THE STUDY AREA 33
4.3 Socio-economic Background of Respondents
As people's perception of water quality may be affected by their socio-economic background (Jacoby, 1972), the socio-economic character- istics of the well users in the study area were obtained during the
interview. This chapter gives a brief profile of these users and the
relationship between the respondents' perception of groundwater quality
and their socio-economic characteristics will be discussed in Chapter 6.
Most of the respondents have lived in their present dwellings
and used groundwater for more than 10 years (Figures 4.1 4.2). The
use of groundwater has thus ingrained into their life. The majority of
the well users have achieved very low education level (Figure 4.3), and
over half of them are over 45 years in age (Figure 4.4). In view of
their age and education background, it can be expected that pollution is
a concept rather new to the majority of the well users.
60.4% of the well users are farmers, engaging in various agri-
cultural activities such as cultivation of vegetables and flowers, cul-
turing of game fishes and edible fishes, and livestock breeding. These
activities normally consume large amount of water. Moreover, the house-
hold income of over half of the respondents are less than H.K. $3,000
per month (Figure 4.5). It can be expected that economy can be one of
the important considerations in their choice of water sources.
Only 9.6% of the respondents' dwellings are used solely for
residential purpose. Others are found either surrounded by the cultivated
land or served as the shelter for both man and livestock. As a result,
the groundwater source is likely to be contaminated by the animal wastes
and chemical fertilizers derived from sources close to the wells. FIGURE 4.2 FIGURE 4.1
CUMULATIVE FREQUENCY DISTRIBUTION OF LENGTH OF TIME THE CUMULATIVE FREQUENCY DISTRIBUTION OF LENGTH OF TIME THE
RESPONDENTS HAVE USED GROUNDWATER RESPONDENTS HAVE LIVED IN THEIR PRESENT DWELLINGS
(n=184) (n=185)
% of total% of total number of number of respondents respondents 100 100
90 90
80 80
"More thin" Ogive "More thin" Ogive 70 70
60 60
50 50
40 40
30 30
20 20
10 10
0 0 0 30 80 40 60 70 10 20 40 50 60 70 0 10 20 30 50 34 Length of time (in years) Length of time (in years) 35
FIGURE 4.3
RESPONDENTS' EDUCATION LEVEL
SECONDARY
EDUCATION
(11.2%)
PRIMARY EDUCATION NO FORMAL (25.7%) EDUCATION (63.1%) FIGURE 4.5 FIGURE 4.4
CUMULATIVE FREQUENCY DISTRIBUTION CUMULATIVE FREQUENCY DISTRIBUTION
OF THE RESPONDENTS' TOTAL MONTHLY INCOME OF THE RESPONDENTS' AGE
(n=187) (n=104)
of total of total number of number of respondents respondents 100 100
90 90
80 80
"More than" 70 "Less than" Oqive 70 Ogive
60 60
50 50
40 40
30 30
20 20
10 10
0 7000 80 0 5000 9000 11000 40 70 1000 3000 10 50 30 60 10000 20 Age (in years) 2000 4000 6000 8000 0 Total Monthly Income (in H.K.$) 36 37
4.4 Summary
Groundwater is used for a great variety of purposes in the
Fanling-Sheung Shui area, including drinking, domestic and agricultural
purposes. In the more remote parts of the study area, groundwater is
the only water source. Most of the well users have low education level
and are engaged in farming activities. Many of them have lived in this
region and used groundwater for a long time. Over half of the respond-
ents can be regarded as belonging to low-class income group. Such
socio-economic characteristics may affect their perception of the quality
of, and the uses they put to groundwater. 38
CHAPTER 5
CHEMICAL DUALITY OF GROUNDWATER
The study conducted by Binnie Partners in 19/2 revealed tnat stream pollution in the New Territories could be ascribed largely to the agricultural wastes derived from pig and poultry rearing. Since such kind of agricultural activity is also common in the Fanling-Sheung
Shui area, it is quite likely that the groundwater in this region has
also been contaminated.
This chapter discusses the chemical quality of groundwater in
the study area and is made up of six sections. The first section des-
cribes the general chemical characteristics of groundwater, the second
attempts to classify groundwater samples and the third evaluates the
suitability of groundwater for drinking, irrigation and industrial pur-
poses. Attempts have also been made to examine the spatial variation
and temporal changes in groundwater quality and the findings are pre-
sented in the fourth and fifth section respectively. Significance of
the results will be discussed in the last section.
5.1 Chemical Characteristics of Groundwater in the Fanling-Sheung Shui
Area
As mentioned in Section 3.1, 215 groundwater samples were col-
lected in August, 1980 and another 206 in December, representing res-
pectively the wet and dry season. Tables 5.1 5.2 list the values
of mean, minimum, maximum, standard deviation and coefficient of vari-
ation of each of the 21 chemical parameters- conductivity (COND), pH, 39
TABLE5. 1
WET-SEASON GROUNDWATERDUALITY- SUMMARYSTATISTICS
Standard Coefficient of Parameter Unit Mean Minimum Maximum Deviation Variation (i)
COND S/cm 313.1 36.2 1287.0 211.0 67.4
pH 6. 2 4.3 8.7 0.7 11.3
K mg/l 6.5 0.1 45.2 6.6 101.5 meq/l 0.16 0 1.15
mg/l 22.8 2.7 109.1 Na 16.1 70.6 meq/l 0.99 0.12 4.74
mg/1 25.8 1.2 161.9 Ca 23.1 89.5 meq/1 1.28 0.06 8.08
0.28 24.30 Mg mg/1 6.12 4.8 78.4 meq/l 0.50 0.02 2.00
0 25.50 NH4-N mg/1 0.27 1.9 703.7 meq/l 0.02 0 1.41
2.0 470.0 HCO3 mg/1 53.2 50.2 94.4 meq/1 0.87 0.03 7.70
147.0 Cl mg/l 32.2 2.5 24.2 75.2 meq/l 0.90 0.07 4.15
121.7 NO3-N mg/l 19.4 0 22.7 117.0 meq/l 0.31 0 1.96
4.35 PO4-P mg/1 0.25 0 0.7 280.0 meq/l 0.01 0 0.14
so4 mg/l 15.4 0 90.1 14.6 94.8 meq/l 0.32 0 1.87
mg/1 13.4 4.1 36.2 5.2 38.8 Si02 Zn mg/l 0.329 0 6.800 0.95 288.8 N.D. Pb mg/l N.D. N.D. N.D. N.D. 666.7 Fe mg/l 0.003 0 0.210 0.02 377.8 Mn mg/1 0.045 0 1.540 0.17 1600.0 Ni mg/1 0.005 0 1.160 0.08 2000.0 Cd mg/l 0.001 0 0.270 0.02 N.D. Cr mg/l N.D. N.D. N.D. N.D. 1000.0 Cu mg/l 0.001 0 0.080 0.01 oc 10.5 WTEMP 27.5 18.1 34.0 2.9 361.1 ss mg/l 5.4 0 240.0 19.5 83.3 TH mg/l 89.6 4.8 504.3 74.6 33.6 PERNA 43.1 7.9 75.9 14.5 63.6 SAR 1.1 0.2 4.0 0.7 10.0 2.5 73.5 TEMPE 0 c 3.4 -2.5
NOTE: N.D.- not detectable COND= conductivity
meq/1- milliequivalents per liter WTEMP- groundwater temperature
SS- suspended solids TH- total hardness
PERNA- per cent sodium SAR- sodium adsorption ratio
TEMPDIF- air temperature minus groundwater temperature 40
TABLE 5.2
DRY-SEASON GROUNDWATERQUALITY- SUMMARYSTATISTICS
Standard Coefficient of Maximum Parameter Unit Mean Minimum Deviation Variation(%)
26.8 1792.0 244.5 80.5 COND uS/cm 303.7 4.3 8.1 0.6 9.4 pH 6.4 80.0 K mg/1 6.0 0.1 8.8 146.7 meq/1 0.15 0 2.05
Na mg/1 23.6 2.2 121.7 19.7 83.5 meq/1 1.02 0.09 5.29
Ca mg/1 27.8 1.7 210.1 35.1 126.3 meq/1 1.38 0.08 10.48
Mg mg/ l 6.19 0.15 48.70 6.1 98.5 meq/1 0.51 0.01 4.00
NH4-N mg/1 0.57 0.01 49.62 3.6 631.6 meq/1 0.03 0 2.75
mg/1 52.3 0 590.0 59.4 113.6 HCO3 meq/1 0.86 0 9.67
Cl mg/1 36.8 2.0 159.0 28.9 78.5 meq/1 1.04 0.05 4.48
NO3-N mg/1 14.8 0.3 112.0 16.3 110.1 meq/1 0.24 0 1.82
16.40 PO4-P mg/1 0.23 0 1.5 652.2 meq/1 0.01 0 0.52
126.5 so4 mg/1 13.4 0 16.0 119.4 meq/1 0.28 0 2.63
44.0 7.2 49.3 Si02 mg/1 14.6 2.0 .19.660 1.97 324.0 Zn mg/1 0.608 0 N.D. N.D. N.D. Pb mg/1 N.D. N.D. 0.150 0.02 1000.0 Fe mg/1 0.002 0 5.910 0.45 368.9 Mn mg/1 0.122 0 4.260 0.30 1304.3 Ni mg/1 0.023 0 1.310 0.09 1285.7 Cd mg/1 0.007 0 M.D. N.D. N.D. Cr mg/1 N.D. N.D. 0.270 0.02 2000.0 Cu mg/1 0.00] 0 10.0 oc 26.0 2.1 WTEMP 21.0 14.0 105.1 602.8 110.3 TH mg/1 104.9 5.1 36.6 80.6 14.9 PERNA 40.7 4.9 3.9 0.7 63.6 SAR 1.1 0.2 -6.0 14. 2.8 140.0 TEMPD 0 c 2.0
CORD= conductivity NOTE: N.D. not detectable
meq/1= milliequivalents per liter WTEMP= groundwater temperature PERNA t per cent sodium TH= total hardness
SAR= sodium adsorption ratio TEMPDIF= a air temperature minus groundwater temperature 41 concentrations of.K, Na, Ca,Mg, ammonium-nitrogen (NH4-N), bicarbonate
(HCO), Cl, nitrate-nitrogen (NO3-N), phosphate-phosphorus (PO4-P), silica (SiO 2), sulphate (SO 4), Zn, Pb, Fe, Mn, Ni, Cd, Cr and Cu
2 physical parameters- water temperature (WTEMP) and concentration of
suspended solids (SS) and 4 other parameters computed from the above
mentioned parameters- total hardness (TH), per cent sodium (PERNA),
sodium adsorption ratio (SAR) and the difference between air temperature
and water temperature (TEMPDIF).
It can be seen that the groundwater of both seasons in this
region are slightly acidic with Ca and Na as the most abundant cations,
and Cl and HCO 3 as the most abundant anions. Pb and Cr could not be
detected in the samples of both seasons. As indicated by the coefficients
of variation, heavy metals, such as Cu, Cd and Ni, exhibit the largest
amount of variability over the study area. Such large variability re-
flects that the concentrations of these constituents can be very different
in different parts of the study area. PO4-P and NH4-N, the two plant
nutrients, also exhibit rather large amount of variability. On the con-
trary, pH and SiO2 show the smallest-amount of variability.
In order to explore the inter-correlation between the solutes in
the groundwater, a correlation analysis was performed. Results are
tabulated for the wet-season and dry-season samples respectively in Tables
5.3 5.4. Conductivity, a measure of the total dissolved matters in
water, is found to be closely related to Mg, Ca and Cl (r 0.80) for
samples of both seasons, 'indicating that increases in dissolved matters
are usually accompanied by increases in Mg, Ca and Cl. Concentrations
of the heavy metals are not significantly related to the conductivity.
Another notable feature that is apparent in Tables 5.3 5.4
is the extremely high degree of inter-correlation between three toxic TABLE 5.3
CORRELATION MATRIX OF CHEMICAL PARAMETERS OF WET-SEASON GROUNDWATER SAMPLES (n=215)
Ca Ni K Na Zn Fe Mn Cd Cu COND HCO3 C1 PO4-P Mg pH Si02 SO4 NH4-N NO3-N
0.75 0.84 COND 0.21 0.44 0.81 0.23 0.75 0.56 0.65 0.88
0.27 0.34 pH 0.42
0.35 0.30 0.44 0.47 0.27 0.21 HCO3 0.34 0.26 0.51 C1 0.24 0.54 0.45 0.46 0.88 0.60
0.28 SiO2 0.70 0.46 0.50 0.45 0.61 SO4 0.34 NH4 -N 0.52 0.74 NO3 -N 0.34 0.81
0.31 0.24 0.23 PO4 -p 0.36 K 0.43 0.42
Na 0.28 0.38
Ca 0.81
Mg
Zn
Fe 0.22
Mn
Ni 1.00
Cd
Cu
NOTE Only correlation coefficients significant at 0.001 level are shown. COND = conductivity 42 TABLE 5.4
CORRELATION MATRIX OF CHEMICAL PARAMETERS OF DRY-SEASON GROUNDWATER SAMPLES (n=206)
NO -N PO -P K Na Ca Mg Zn Fe Mn Ni Cd Cu COND pH HCO3 Cl SiO2 SO4 NH4 N 3 4'
IID 0.62 0.81 0.23 0.65 0 .49 0.61 0.42 0.59 0.66 0.84 0.92 0.21 0.22 0.22 0.22 COND
0.53 0.21 0.30 PH
0 0.36 0.45 0.70 0.67 0.65 0.42 0.40 0.51 HCO3 0.32 .0.49 0.37 0.43 0.89 0.54 0.67 CI 0 0.32 0.24 0.26
SiO2 0.26 0.29 0.22 0.42 0.47 0.59 0.59
SO4 0.75 0.58 0.23 0.52 NH4 -N 0.81 0.67 0.43 0.43 0.43
NO3 -N 0.34 0.40 0.29 PO4 -P 0.44 0.36 0.53 K 0.34 0.48 Na 0.82 0.29 0.29 0.30 Ca 0.22 0.26 0.26 0.27
Mg
Zn
Fe
Mn 1.00 1.00 Ni
Cd 3 i! 1.00
Cu
NOTE: Only correlation coefficients significant at 0.001 level are shown. COND= conductivity 43 44
heavy metals- Ni, Cd and Cu (r= 1.00) especially in the dry-season
samples, probably suggesting that they are derived from similar origins.
Na and Cl are found to be closely related to each other (r>0.80).
Besides, high degree of inter-correlation also exists between Ca and
NO3-N (r>0.80).
5.2 Classification of Groundwater Samples
In view of the large magnitude of variability in the original
data, average concentration figures are not particularly meaningful in
describing the water quality. Attempts have thus been made to classify
the water samples so that more representative statistics can be calculated
for each group. Piper's trilinear diagram and cluster analysis were em-
ployed for such purpose. Piper's trilinear diagram is a traditional
method derived in 1950's for the classification of water types and hydro-
chemical facies of groundwater, whereas cluster analysis is a modern
statistical technique to group a number of observations based on all their
measured attributes simultaneously.
5.2.1 Hydrochemical Facies of the Groundwater
Piper's trilinear diagram permits the cation and anion com-
positions of many samples to be represented on a single graph in which
major groupings and differences in major-ion chemistry of the ground-
water samples can be discerned visually. The groundwater is treated
substantially as though it contained three cation constituents (Na, Ca and Mg) and three anion constituents (Cl, SO4 and HCO3). The other less
abundant constituents such as K and carbonates (CO3) are summed with the
major constituents to which they are related in chemical properties.
The diagram (Figure 5.1) combines three distinct fields for
plotting, two triangular fields at the lower left and lower right, res-
Dectivel, and an intervening diamond-shaped field. All three fields 45
FIGURE 5.1
CLASSIFICATION DIAGRAMS FOR WATER TYPES AND HYDROCHEMICAL FACIE
IN TERMS OF MAJOR-ION PERCENTAGES
(Modified from Piper, A.M., 1953, "A Graphic Procedure in the Geochemical Interpretation of Water Analyses", U.S. Geol. Surv. Ground Water Note 12 quoted by Walton, 1970.)
50 6 50 50 9 1 4 75 2 3 9 50 50 50 8 50 50 Ca+Mg SO4+Cl Subdivisions of diamond-shaped field of Piper's trilinear diagram.
Magnesiun Sulfate Na+K type type Mg 50 50 SO CO3+HCO3 4 No No dominant dominant Car- type type Sodium bonate
Calcium + potas- + bicar- Chloride type sium type bonate type type
50 50 Percentage Reacing Values CATIONS Ca C1 ANIONS
Water samples are classified according to the domain in which they occur on the diagram segments:
Area 1: alkaline earths exceed alkalies. Area 2: alkalies exceed alkaline earths. Area 3: weak acids exceed strong acids. Area 4: strong acids exceed weak acids. Area 5: carbonate hardness exceeds 50%- that is, chemical properties of the groundwater are dominated by alkaline earths and weak acids. Area 6: noncarbonate hardness exceeds 50%. Area 7: noncarbonate alkali exceeds 50% - that is, chemical properties are dominated by alkalies and strong acids. Area 8: carbonate alkali exceeds 50%. Area 9: no one cation-anion pair exceeds 50%. 46
have scales reading in 100 parts. At first, the sub-total of all cation milliequivalents per litre (meq/1) is taken as the 100 percent base for computing percentage reacting values of the several cation variables and likewise for the several anion variables. In the triangular field at the lower left, the percentage reacting values of the three cation groups (Ca. Mg and Na plus K) are plotted as a single point according to conventional trilinear co-ordinates. The three anion groups (Cl,
SO4 and HCO3 plus CO3) are plotted likewise in the triangular field at the lower right. Four water types can be classified for each triangular field (Figure 5-1).
The central diamond-shaped field is used to show the overall chemical character of the groundwater by a third single-point plotting, indicating the relative composition of a groundwater in terms of the cation-anion pairs that correspond to the four vertices of the field.
Distinct hydrochemical facies of the groundwater can be discriminated by their plottings in certain subareas of the diamond-shaped field.
Hydrochemical facies are distinct zones that have cation and anion con- centrations describable within defined composition categories (Freeze
Cherry, 1979). The definition of a composition category is commonly based on subdivisions of the diamond-shaped field of the trilinear diagram in the manner shown in Figure 5.1.
The groundwater samples of wet-season and dry-season are plotted in Figure 5.2 5.3 respectively. The percentages of various water types and hydrochemical facies as portrayed by these figures are summarized in Table 5.5. Results for both seasons are similar. For the cations, the two dominant water types are Ca and Na+ K whereas for the anions, Cl and HCO3 types are the msot dominant. With regard to the hydrochemical facies, it can be seen that there is no single dominant group. 45t of the samples (area 9) could not be assigned to any of the distinct facies. Of the rest, it can be observed that Na and K are 80 80
60 60
Ca+ Mg SO4+ Cl 40 40
20 20
20 20
80 80
40 40
60 60 80 MG SO4 60 CO3+HCO3 60 40 40
80 80
20 20
80 60 40 47 40 20 20 60 80 Ca Cl FLGURE 5.2 GROUPENGS OF WATER TYPES AND HYDROCHMICAL FACIES OF THE OET-SEASON GROUNDWATER SAMPLES 80 80
60 60 CI
SO Ca + Mg 40
20 20
20 20
80 80
40 40
60 60
Na + K SO 60 CO3+HCO3 60 Mg
40 40
80 80
20 20
48 80 60 40 20 60 Ca 20 40 80 GROUPINGS OF WATER TYPES AND HYDROCHEMICAL FACIES OF THE DRY-SEASON GROUNDWATE 49
TABLE 5.5
CLASSIFICATION OF WATER TYPES AND HYDROCHEMICAL FACIES
Percentage of Samples
Grouping Wet-season (n=211) Dry-season (n=206)
Water Type:
For Cation Groups-
Mg type 0 0
Ca type 26.5 34.0
Na + K type 34.6 26.7
No dominant type 38.9 39.3
For Anion Groups-
SO4 type 0.5 0.5
Cl type 38.4 46.6
HCO3 + CO3 type 35.5 33.5
No dominant type 25.6 19.4
Hydrochemical Facies:
Area 5: carbonate hardness
(Ca, Mg HCO3) exceeds 24.2 19.6 50%
Area 6: non-carbonate hardness
(Ca,Mg SO4,Cl) exceeds 7.6 9.2 50%
Area 7: non-carbonate alkali
(Na,K SO4,Cl) exceeds 23.2 22.8 50%
Area 8: carbonate alkali
(Na,K HCO3) exceeds 0 0
50% Area 9: no one cation-anion 4.5 38.4 pair exceeds 50% 50 usually associated with SO4 and Cl; whereas Ca and Mg with HCO3.
The dominance of Na, Ca, K and HCO3 can be explained by the chemical weathering of the fine welded tuff (Figure 2.2 on p.13) in the study area. As indicated by the equations shown in Table 5.6, hydrolysis of the silicate minerals of the welded tuff releases SiO2, Na, Ca, K and
HCO3 to the groundwater. This is also confirmed by the relative mobility sequence of these ions found by Liu (1981), as discussed in Chapter 2.
To test the above supposition, the groundwater quality data were plotted on four stability field diagrams (Figures 5.4 5.5). It can be seen that the groundwater samples of both seasons mainly fall within the kaolinite field, which is the final product of the chemical weathering of volcanic tuff in the study area. The fact that the groundwater samples are in equilibrium with the weathering products is an indication that
chemical weathering of the volcanic tuff is one of the controlling mechan-
isms of the chemical composition of the groundwater in the study area.
However, no chloride is released from these weathering reactions (Table 5.6)
because there is virtually no chloride bearing minerals in volcanic rocks,
and the chloride present in the groundwater is probably derived from
anthropogenic sources.
5.2.2 Cluster analysis os Groundwater Samoles
Piper's graphical method to classify groundwater samples has
one serious drawback. Limited by the number of dimensions that could be
graphically represented, some chemical parameters have to be combined
(e.g. Na with K, Cl with SO4); thus entailing loss of some information.
This drawback can be overcome by cluster analysis, which can take into
account a great number of dimensions (i.e. chemical attributes). The
procedures and application of cluster analysis can be found in many texts
although it has not been widely used in pollution studies. In this study,
the Statistical Analysis System (SAS) was employed. Since the clusters 51
TABLE 5.6
WEATHERING REACTIONS OF THE MAJOR FINE WELDED TUFF
FORMING MINERALS (After Liu, 1981)
1. Orthoclase (K-Felspar)- Kaolinite
2KAISi3O8 + 2CO2 +3H2O AI2Si2O5(OH)4 + 2K +4SiO2 + 2HCO3
(orthoclase) (kaolinite)
2. Albite (Na-Felspar)- Kaolinite
2NaAISi3O8 + 2CO2 +3H2O AI2Si2O5(OH)4 + 2Na +4SiO2 +2HCO3
(albite) (kaolinite)
3. Anorthite- Kaolinite
CaAI2Si2O8 +2CO2 +3H2O AI2SI2O5(OH)4 +Ca +2HCO3
(anorthite) (kanlinite)
4.- Diopside
CaMgSi2O6 +4CO2 +2H2O Ca +Mg +2SiO2 +4HCO3
(diopside)
5. Hyperstnene
(Mg,Fe)SIO3 +2CO2 +H2O (Mg,Fe) +SiP2 +2HCO3
(hypersthene) FIGURE 5.4
STABILITY FIELD DIAGRAMS FOR ALUMINIUM SILICATES-AQUEOUS SOLUTION
SHOWING GROUNDWATER COMPOSITION (WET-SEASON)
13 10 18 8 Anorthite low albite 17 7 12 Mg-chlorite 9 K-mica
8 16 6 11 Microcline 7 15 5 10
14 4 9 6
Mg-mont. Na-mont. log[Ca]+ log[Mg]+ log[k]+3 8 log[Na]+5 13 Ca-montmorillonite Kaolinite
2pH Gibbsite pH 2pH pH 12 Kaolinite 2 7 4
Gibbsite Gibbsite Gibbsite
11 1 6 3
2 10 0 Kaolinite 5 Kaolinite amorphous amorphous amorphous amorphous 1 9 -1 4
quartz quartz SiO2 sio2 quartz sio2 SiO2 8 -2 3 quartz 0
sat sat sat. sat. sat. sat sat sat. 7 -3 2 -1
-6 -5 -4 -3 -6 -5 -4 -3 -6 -5 -4 -3 -6 -5 -4 -3
log(H SiO) log(H SiO) log(H SiO) log(H SiO) 4 4 4 4 4 4 4 4 52 FIGURE 5.5
STABILITY FIELD DIAGRAMS FOR ALUMINIUM SILICATES-AQUEOUS SOLUTION
SHOWING GROUNDWATER COMPOSITION (DRY-SEASON)
13 10 18 8 Anorthite Iow Mg-chlonite albite 7 12 9 17 K-mica
8 16 6 11
Microcline 5 10 7 15
6 14 4 9 log[Mg] Mg-mont. log[Na+] Na-mont 13 log[K+]3 8 5 Ca-montmorillonite+
+2pH +pH Gibbsite 4 Gibbsite log[Ca++]12 Gibbsite pH 2 Gibbsite 7 Kaolinite Kaolinite
11 1 6 3
Kaolinite Kaolinite 0 2 10 5 amorphous amorphous amorphous amorphous 9 -1 4 1 quartz quartz Sio2 sio2 quartz Sio2 quartz sio2 8 -2 3 0
sat. sat. sat. sat. sat. sat. sat. sat. 7 -3 2 -1
-6 -5 -3 -6 -5 -4 -3 -5 -3 -4 -6 -4 -6 -5 -4 -3
log(H4Sio) log(H4Sio4) log(H4Sio4) log(H4Sio4) 53 54
were delimited arbitrarily from the dendogram, it was necessary to test whether there are significant differences between the clusters so defined by means of a multiple discriminant analysis. The discriminant analysis can also be employed to examine previously grouped observations, and to
re-classify any misclassified and unclassified observations (Nie et al.,
1975). The discriminant analysis of the Statistical Package for the
Social Sciences (SPSS) was used for this study.
In this study, only major cations (K, Na, Ca, Mg) and anions
(HCO3, Cl, SO4, NO3-N) were included in the cluster analysis. There are
two reasons why it was necessary to exclude the trace elements. Firstly,
it could eliminate any undue influence caused by the trace elements in
the process of clustering. Secondly, by excluding the trace elements,
results of the cluster analysis are directly comparable to those by the
Piper's method. The dendogram provided by the cluster analysis suggested
that the samples of wet season could be divided into five groups. Because
of the large number of cases, it is impossible to reproduce the dendogram
in this thesis. As mentioned in the preceding paragraph, the validity of
this grouping had to be assessed by the discriminant analysis. According
to the Wilks' Lamda test, the five groups defined by cluster analysis are
significantly different at 0.001 level. Results in Table 5.7 show that
the first three discriminant functions can account for 80% of the total
variance and also that the anions have greater discriminatory power than
the cations. In other words, the cluster groups were classified more
according to the anionic composition (Cl, HCO3, SO4) than to the cationic
composition. Results of the classification show that only 11 cases pre-
viously clustered had been misclassified and only one case could not be
classified. Table 5.8 shows the number of water samples and the chemical
characteristics of each group in terms of the major ionic composition. TABLE 5.7
RELATIVE CONTRIBUTION OF EACH WATER QUALITY PARAMETER
TO EACH DISCRIMINANT FUNCTION (WET-SEASON SAMPLES)
Water Quality Parameter Eigenvalue (%)
Cl NO3 -N SO4 HCO3 Ca K Na
Discriminant -1.110 -0.210 -0.094 0.025 0.146 0.047 0.195 45.4 Function 1
Discriminant 0.457 -0.435 -0.001 0.270 -0.678 0.103 0.147 29.5 Function 2
Discriminant -0.161 -0.874 0.926 -0.945 0.280 0.044 0.239 15.1 Function 3
Discriminant 0.476 -0.538 -1.030 -0.800 0.784 0.017 0.190 8.1 Function 4
*After entering of Na on step number 7,F level became insufficient for further computation
55 HCO Cl SO NO -N Conductivity% of Group (WET-XEASON SAMPLES)
Conductivity of Group
K Na Ca Mg HCO3 Cl SO4 NO3-N (s/cm) Samples Characteristics
Mean Mean 5.2 16.5 18.6 4.57 49.4 21.4 10.3 10.5 295.5 (mg/1) (mg/1)
Coefficient of Coefficient of 104.1 52.7 44.1 60.6 85.3 58.9 69.9 117.1 55.7 75.1 Ca(Na)HCO3(Cl) Group I Variation (％) Variation (％)
Major Cation Major Anion 6.0 33.3 43.1 17.6 45.3 33.5 11.7 9.5 Percentage Percentage
Mean Mean 11.5 37.1 38.4 8.45 78.3 52.8 41.3 16.3 573.7 (mg/1) (mg/1)
Coefficient of Group II Coefficient of 57.5 41.0 70.5 59.0 54.9 37.7 42.0 181.8 32.9 10.5 Variation( ) Variation (%) Ca(Na)Cl(HC03)
Major Cation Major Anion 6.4 35.6 42.5 15.5 32.9 38.3 22.1 6.7 Percentage Percentage
Mean Mean 4.7 48.2 22.6 6.81 l 28.9 76.5 11.9 16.6 469.5 (mg/1) (mg/1)
Group III Coefficient of Coefficient of 46.9 35.7 27.4 24.8 49.6 26.1 67.7 72.9 18.2 5.8 NaC1 Variation(%) Variation(%)
Major Cation Major Anion 3.1 53.7 28.9 14.3 Percentage Percentage 14.9 68.6 7.9 8.6
Mean Mean 9.6 23.1 83.6 19.8 42.4 56.8 32.4 64.7 806.2 (mg/1) (mg/1)
GroupIV Coefficient of Coefficient 82.5 59.9 36.5 24.8 54.0 23.4 36.8 38.3 23.6 6.7 Ca;Cl Variation (%) Variation(%)
Major Cation Major Anion 3.5 14.2 59.2 23.1 Percentage Percentage 17.3 40.0 16.7 26.0
Mean Mean 26.1 72.0 41.3 11.66 l 96.3 108.0 35.9 20.4 737.9 (mg/1) (mg/1)
Group V Coefficient of Coefficient of 46.2 24.7 19.4 49.7 18.5 1. Na (Ca); Cl Variation (%) 68.6 24.3 24.7 27,9 Variation (%)
Major Cation Major Anion 9.8 45.9 30.2 14.1 Percentage Percentage 27.7 53.4 13.1 5.8 56 57
A striking feature that is evident in Table 5.8 is the very large number of samples assigned to group I. The most abundant ions of this group are Ca and HCO3 and are closely followed by Na and Cl. The total solute level, as indicated by conductivity, is the lowest among all groups. Group II is dominated by Ca and Cl, followed closely by Na and HCO3. Group III and V are dominated by Na and Cl whilst group IV by
Ca and C l.
Using conductivity as an indicator of the stage in the hydro-
chemical evolution of groundwater, it can be seen from Table 5.8 that
there is a tendency for groundwater to evolve from Ca dominance to Na
dominance, and from HCO3 dominance to Cl dominance. This is expected
because the chemistry of uncontaminated groundwater is controlled largely
by the chemical interactions between the aluminosilicate minerals of the
welded tuff and the soil water. As described in the above section, the
dominant ions released from the chemical weathering processes are Ca, Na
and HCO3. These are the principal components of group I. On the other
hand, groundwater may pick up more and more solutes of anthropogenic
origin along its pathway of movement. Since Na and Cl are the major
constituents of domestic sewage, it is not surprising that these two
ions become the more abundant ions in the later stage of the chemical
evolution of groundwater in the study area.
5.3 Suitability of the Groundwater for Various Uses
Most interpretations of groundwater quality data are made to
determine whether the water is satisfactory in quality for a proposed
use. This depends on the standards'of acceptable quality for that use.
Quality standards of water supplies for drinking, agricultural and
industrial purposes will now be described and compared with the chemical
quality of the groundwater in the study area. 58
5.3.1 Drubking Purpose
Groundwater is one of the major sources of drinking water in the study area. Over 70% of the respondents use groundwater for drinking purpose.
Different drinking water standards have been set up by dif- ferent organizations, such as the U.S. Public Health Service (1962), the
World Health Organization (1971) and the U.S. Environmental Protection
Agency (1975). On the whole, there are only minor differences between these three schemes. In this study, the more comprehensive Internationa:
Standards for Drinking Water (Table 5.9) recommended by the World Health
Organization (1971) have been used for comparison with the data obtained in the study area.
Table 5.10 presents the percentage of wells used for drinkinc purpose that exceeded the highest desirable levels of those constituents analysed in the present study. It can be seen that concentrations of heavy metals (Cu, Cd, Cr) of all but one case (0.5%) are below the high- est desirable levels. Very high concentration of Cd was recorded for a sample taken from Loi Tung Tsuen East (Refer to Figure 2.1 on p.12), deriving from empty dye-chemical containers outside a nearby cottage
factory. Since Cd is highly toxic to human beings, its presence in high concentration in the drinking water can cause nausea and vomiting.
It can also be accumulated in the liver and kidney of the user.
The total hardness of about one-third of samples of both seasons exceeds the recommended limit. High level of total hardness is one of the domestic problems in this region because of the excessive scale formation- chalky deposits inside boilers, kettles and water- pipes. Furthermore, the pH of 90.5% of wet-season samples and 85.4% of drv-season samples are outside the recommended ranqe. Table 5.11 lists TABLE 5.9
INTERNATIONAL STANDARDS FOR DRINKING WATER
TENTATIVE LIMITS FOR TOXIC SUBSTANCES IN DRINKING WATER
Substance Upper Limit of Concentration (mg/1)
Arsenic (as As) 0.05 Cadmium (as Cd) 0.01 Cyanide (as CN) 0.05 Lead (as Pb) 0.1 Mercury (total as Hg) 0.001 Selenium (as Se) 0.01 *Chromium (as Cr Hexavalent) 0.05 *Barium (as Ba) 1.0 *Silver (as Ag) 0.05
SUBSTANCES AND CHARACTERISTICS AFFECTING THE ACCEPTIBILITY OF WATER 'nnMFCTT TTci
Substance Highest Desirable Level Maximum Permissible Level
pH range 7.0 to 8.5 6.5 to 9.2 Total hardness (as CaCO3) 100 mg/l 500 mg/l Chloride (as Cl) 200 mg/l 600 mg/i Calcium (as Ca) 75 mg/l 200 mg/i 0.05 'mg/1- Copper (as Cu) 1.5 mg/l Iron (as Fe) 0. 1 mg/l 1.0 mg/i Magnesium (as Mg) Not more than 30 mg/l 150 mg/l if there are 250 mg/1 of sulfate if there is less sulfate, magnesium up to 150 mg/l may be allowed. Manganese (as Mn) 0.05 mg/l 0.5 mg/l Sulfate (as SO4) 200 mg/l 400 mg/l Zinc (as Zn) 5.0 mg/l 15.0 mg/l *Nitrate nitrogen 10 mg/l *Ammonium nitrogen 0.04 mg/l *Total dissolved solids 500 mg/l
*U.S. Environmental Protection Agency Proposed National Interim Primary Drinking Water Standards (SOURCE: National Water Well Assoc., 1975).
SOURCE: World Health Organization (1971), quoted by Frits van der Leeden,
1975. 60
TABLE 5.10
COMPARISON BETWEEN THE CHEMICAL QUALITY OF GROUNDWATER AND THE DRINKING
WATER STANDARDS SET BY THE WORLD HEALTH ORGANIZATION (1971)
Percentage of Wells used for Drinking I Substance Highest Desirable Purpose that exceeded the Limit Level Wet-season Dry-season
(n=211) (n=206)
Cu 0.05 mg/1 0.5 0
Cd 0.01 mg/1 0.5 o.5
Cr 0.05 mg/1 0 0
Fe 0.1 mg/1 1.0 1.0
Mn 0.05 mg/1 15.6 31.1
Zn 5.0 mg/1 1.4 2.9
Ca 75 m/1 3.8 11.2
Mg Not more tnan su mg/l 0 0 if there are 250 mg/l of sulfate if there is less sulfate, mag- nesium up to 150 mg/l may be allowed.
Cl 200 mg/1 0 0
NO3-N 10 mg/1 54.5 36.4
NH4-N 0.04 mg/1 20.9 93.2
so4 200 mg/1 0 0
Total 100 mg/1 34.1 36.9 Hardness
90.5 85.4 pH 7.0 to 8.5 61
TABLE 5.11
EFFECTS CAUSED BY THE EXCESSIVE AMOUNTS OF INORGANIC CONSTITUENTS
IN GROUNDWATER
Substance Nature of Trouble or Effect which may arise
Cd causes nausea and vomiting, accumulates in the liver and kidney, recognized carcinogen.
Cr iausea, ulcers after long-term exposure trivalent form harmless.
Total 3xcessive scale formation danger of dissolving heavy metals if hardness the level of hardness is below the recommended limit.
pH taste, corrosion.
Cl imparts taste at concentrations above 400 mg/l corrosion in hot. water systems no known health effects.
Cu disagreeable taste above 1 mg/l discoloration and corrosion of pipes, fittings and utensils.
Fe high levels impart an unattractive appearance and taste no health effects discoloration deposits and growth of iron bacteria turbidity.
NH4-N growth of organisms danger of corrosion in pipes difficulties in chlorination.
NO3-N high levels have been associated with methemoglobinemia and diarrhoea affect cardiac function cause an earlier onset of
hypertension.
so4 at high concentrations, has a laxative effect on new users no permanent effects gastrointestinal irritation when combined with magnesium and sodium.
Total very high levels have cathartic reaction and do not quench dissolved thirst. solids
Mn disagreeable taste discolors laundry not considered health hazard in water because of unpleasant taste and other dietary sources deposits in pipes turbidity.
Zn astringent taste above 5 mg/l higher concentrations give milky appearance and form a greasy film upon boiling very high concentrations associated with nausea and fainting.
Ca excessive scale formation.
Mg hardness taste gastrointestinal irritation in the presence of sulfate.
SOURCES: Tate Trussell (1977) and Frits van der Leeden (1975). 62
the nature of domestic troubles and health effect which may arise if certain constituents are present in excessive amounts.
Since agriculture is a dominant land use in the study area, one may expect high concentrations of nitrates and phosphates in the groundwater. In fact, high concentrations of NO3-N have been found in
54.5% of wet-season samples and 36.4% of dry-season samples. The high
NO3-N content may pose health risks for inhabitants who use groundwater for drinking purpose. It can cause methaemoglobinaemia which can be fatal among infants. This is a consequence of the reduction of nitrates to nitrites by the intestinal bacteria, and the subsequent entrance of nitrites into the blood and reaction with hematin- a component of hemoglobin. This in turn reduces the oxygen-transporting function of
the blood.- The effect of nitrate in adults is less marked, but it has been reported that nitrate can impair the cardiac function and cause an
earlier onset of hypertension (Malberg et al., 1978). Moreover, nitrites
can react with amines to form the nitroso-amine compounds which are widely
acknowledged to be carcinogens (Hui Mao, 1979). But no case of the
mentioned diseases can be confirmed-in Hong Kong.
Concentrations of SO4, Cl, Mg and Pb of all the samples from
the wells used for drinking purpose in this study are below the recom-
mended levels.
5.3.2 Irrigation Purpose
52.9% of the respondents use groundwater for irrigation pur-
pose. Sodium concentration is one of the important parameters for de-
termining the quality of an irrigation water because sodium can reduce
the permeability of the soil (Todd, 1959). It can be expressed in terms
of per cent sodium (also known as sodium percentage and soluble-sodium
percentage), defined by 63
per cent sodium
where all ionic concentrations are expressed in milliequivalents per
litre (meq/l).
From Table 5.12, it can be seen that in both seasons, over
40% of the groundwater samples used for irrigation purpose are classified
as excellent or good. Only 0.5% of the dry-season samples belong to
the unsuitable water class.
Another index that assesses the suitability of water for
irrigation is the sodium adsorption ratio (SAR), proposed by the Salinity
Laboratory of the U.S. Department of Agriculture. It is defined by
sodium adsorption ratio
where the concentrations of the constituents are also expressed in meq/l.
From Table 5.12, it was found that all the samples used for
irrigation purpose in this study are classified as excellent.
5.3.3 Livestock Production
Groundwater is used by 44.4% of the respondents for the rear-
ing of pigs, chickens, ducks and pigeons in the study area. Table 5.13
presents the recommended concentration limits for water used for live-
stock production set by U.S. Environmental Agency (1973). It was found
that only the NO a -N concentration of 4% of the groundwater samples col-
lected from the wells used for livestock rearing exceed the recommended
limit. Cd, Cr and Pb concentrations of all the samples are below the
limits.
5.3.4 Industriat Purpose
The quality requirements of water used in different industries
can vary widely. Even within a particular industry, no uniform criteria
can he established. Thus only tentative limiting values or ranges can be 64
TABLE 5.12
COMPARISON BETWEEN THE CHEMICAL QUALITY OF GROUNDWATER
AND THE IRRIGATION WATER STANDARDS (Todd, 1959)
Percentage of groundwater samples Water Class Per Cent Sodium used for irrigation purpose that
within the limit (n=106)
Wet-season Dry-season
Excellent < 20 6.6 11.2
Good 20- 40 35.5 31.5
Permissible 40- 60 45.5 48.5
Doubtful 60- 80 12.4 8.3
Unsuitable > 80 0 0.5
Percentage of groundwater samples Water Class Sodium Adsorption Ratio used for irrigation purpose that within the limit (n=106)
Wet - season Dry - season
Excellent < 10 100.0 100.0
Good 10- 18 0 0
Fair 18- 26 0 0
Poor 26 0 0 65
TABLE 5.13
RECOMMENDED CONCENTRATION LIMITS FOR WATER USED FOR
.,IVESTOCK PRODUCTION
Constituent Recommended Limits (mg/1)
*Total dissolved solids:
Small animals 3000
Poultry 5000
Other animals 7000
*Nitrate 45
Arsenic 0.2
Boron 5
*Cadmium 0.05
*Chromium 1
Fluoride 2
*Lead 0.1
Mercury 0.01
Selenium 0.05
Items measured in this study
SOURCE: U.S. Environmental Agency (1973), quoted in Freeze Cherry (1979). 66 recommended. A proposed water quality standard for industrial uses by Nemerow (1971) is reproduced in Table 5.14.
In this region, only very few small-scale or cottage in-
dustries are still using groundwater for their production processes.
Such industries are found in Hung Leng Tsuen East, Ta Shek Wu and Kwan
Tei Tsuen North (Refer to Figure 2.1 on p.12). The former two are food- manufacturing factories (noodles and bean products like bean-curbs, dried bean-milk rolls and sprouted broad bean). The latter is a dyeing factory,
the groundwater sample from which was found to contain concentrations of
Mn and total hardness (88.9 mg/l for wet-season and 111.7 mg/l for dry-
season sample) higher than the recommended limits for textile dyeing.
High levels of total hardness can damage or reduce the efficiency of
boilers.
5.3.5 Summary
The above comparison between the chemical quality of ground-
water of the study area and the water quality standards indicates that
chemical contamination of groundwater did exist in some parts of the study
area. High NO3-N level was for example detected in nearly half of the
samples. The groundwater with high content of NO3-N is particularly
suitable for irrigation purpose. The chemical quality of groundwater
in most parts of the-study area is satisfactory for a number of uses
other than drinking.
5.4 Spatial Variation of Groundwater Quality in the Study Area
5.4.1 Spatiat pattern pf water Quatity Gnoups
Results of cluster analysis presented in Section 5.2.2 show
that the wet-season groundwater samples can be subdivided into five
groups of different chemical compositions (Table 5.8). To examine whether
there is any spatial pattern of groundwater quality in the study area,
the locations of different groups of groundwater samples were plotted on TABLE 5.14
WATER QUALITY STANDARDSFOR INbUSTRIAL USE
Total Alkalinity Hardness Suspended Iron Manganese NO3 Dissolved SiO2 Ca Mg HCO3 Colour Chloride (CaCO3) pH SO4 Solids Industry and Process (CaCO3) (mg/l) (mg/1) Solids (mg/1) (mg/1) (mg/1) (mg/1) (mg/l) (mg/1) (mg/1) (mg/1) (mg/1) (mg/1) (mg/1) (mg/1)
Textiles: Size 5 25 0.3 0.05 6.5-10.0 100 5.0 Scouring 5 25 0.1 0.01 3.0-10.5 100 5.0 Bleaching 5 25 0.1 0.01 2.0-10.5 100 5.0 Dyeing 5 25 0.1 0.01 3.5-10.0 100 5.0 raper: Mechanical 30 1000 0.3 0.1 6.0-10.0 Chemical Unbleached 30 200 100 1.0 0.5 6.0-10.0 10 50 20 12 Bleached 10 200 100 0.1 0.05 6.0-10.0 10 50 20 12
Chemicals: 100 Alkali and chlorine 10 80 140 0.1 0.1 6.0-8.5 10 40 8 Coal tar 5 50 30 180 0.1 0.1 6.5-8.3 200 400 5 50 14 60 Organic 5 125 25 170 0.1 0.1 6.5-8.7 75 250 5 50 12 128 Inorganic 5 70 30 250 0.1 0.1 6.5-7.5 90 425 5 60 25 210 Plastic and resin 2 1.0 0 0 0.005 0.005 0 7.5-8.5 0 1.0 2.0 0.02 0 0 0.1 Synthetic rubber 2 2 0 0 0.005 0.005 0 7.5-8.5 0 2.0 2.0 0.05 0 0 0.5 Pharmaceutical 2 2 0 0 0.005 0.005 0 7.5-8.5 0 2.0 2.0 0.02 0 0 0.5 Soaps and detergent 5 50 40 130 0.1 0.1 150 300 10.0 30 12 60 Paints 5 100 30 150 0.1 0.1 6.5 125 270 10 37 15 125 Gum and wood 20 200 500 900 0.3 0.2 5 6.5-8.0 100 1000 30 50 100 50 250 Fertilizer 10 175 50 250 0.2 0.2 5 6.5-8.0 150 300 10 25 40 20 210 Explosives 8 100 30 150 0.1 0.1 2 6.8 150 200 5 20 20 10 120 Petroleum 300 350 1.0 6.0-9.0 1000 10 75 30
Iron and steel: Hot-rolled 5.0-9.0 Cold-rolled 5.0-9.0 10
liscellaneous: Fruit and vegetable canning 5.0 250 250 250 0.2 0.2 10 6.5-8.5 250 500 10 50 100 Soft drinks 10 85 0.3 0.05 Leather tanning 5 250 150 50 6.0-8.0 250 60
Cement 400 250 25 0.5 6.5-8.5 250 600 500 35
OURCE: Nemerow, N.L. (1971). Liquid waste of industry: theories, practices and treatment, London: Addison-Weseley Publ. Comp. (quoted by F. Goeltenboth, 1979) 67 68
a map (Figure 5.6).
It can be seen that no well defined spatial pattern can be depicted. However, samples of group IV, characterized by relatively high levels of solute concentration were found clustered around Hung
Leng Tsuen and Loi Tung Tsuen which are the two of most densely populated villages in the north-eastern part of the study area (The Census and
Statistics Department, 1971). On the contrary, samples taken from wells
located along the River Beas, where the population density is relatively
low, all belonged to group I, the group with the lowest solute concen-
tration. This suggests that population density may be one of the factors
which affect groundwater quality. The statistical relationship between
the population density and solute concentration will be discussed in
greater details in the next section.
5.4.2 Human Factors offecting the Chemicat Quatity of Gnounduater
In an attempt to investigate the human factors which affect
the chemical quality of groundwater, a correlation analysis was carried
out. Four chemical parameters (conductivity, NH4-N, NO3-N and PO4-P)
were chosen as the dependent variables. Conductivity was chosen because
it is generally considered as a measure of total solute, and NO3-N was
chosen because of its potential health risks to those who consume the
water. NH4-N is an indication of recent sewage contamination, and PO4-P
is a major plant nutrient, which together with NO3-N, can enhance eutro-
phication of water bodies. The independent variables are the three human
factors which can be easily measured and which are believed to be the
major pollution sources. They are the number of inhabitants (POP), pigs
(PIG) and poultry (POUL) and were obtained from the Census and Statistics
Department (1971) and the Agriculture and Fisheries Department (1979).
In order to determine whether the chemical quality of the N
R. Indus R. Sutlein
R.Beas R. Chenab R.Jhelum
R. Lung
FIGURE 5.6 SPATIAL DISTRIBUTION OF THE WATER Group I QUALITY GWOUPS (WET~SEASON CASES Group II Group III
0 1 2km Group IV Group V 69 70 groundwater is affected by the large-scale pollution source or by minor pollution sources located near to the well, the correlation analysis was carried out at two different levels- the well level and the village
level. At the well level, the chemical composition of the groundwater of each well was correlated with the number of inhabitants, pigs and poultry at the dwelling unit where the well was located. The data of the dry-season were used. At the village level, the correlation analysis was
carried out using the mean chemical composition of groundwater collected
from each village, and the number of inhabitants, pigs and poultry of that
village. Villages from which less than three water samples had been col-
lected were discarded in the analysis.
With regard to the well level, it can be seen that no signi-
ficant correlation exists between any pair of dependent and independent
variables (Table 5.15). This indicated that groundwater quality was not
determined by landuses in the vicinity of the well.
Results for the village level are slightly different. From
Tables 5.16 5.17, it can be seen that fairly high positive correlation
exists between COND and POP for both seasons. This reveals that increases
in the solute level of groundwater are related to the increase in population
size. This is expected because domestic sewage contains high levels of
dissolved salts and, as discussed in previous chapters, is a major source
of groundwater contamination. Further analysis was undertaken to see
whether or not this correlation is spurious by means of partial correlation.
After controlling the two other variables- PIG and POUL, results show that
the partial correlation coefficient between COND and POP has not decreased
substantially (Tables 5.18 5.19) and is still statistically significant.
Therefore, it may be concluded that the number of inhabitants is one of
the human factors which can cause increases in solutes, and hence con- TABLE 5.15 PEARSON BETWEEN FOUR CHEMICAL PARAMETERS AND THE 71 HUMAN FACTORS (DRY-SEASON CASES AT THE "WELL LEVEL")
Human Factor
POP PIG POUL
0.10 *-0.15 *-0.15 COND (s=.094) (s=.023) (s=.020)
Chemical 0.01 -0.04 0.10 (a NH -N 4 (s=.079) (s=.307) (s=.091)
0.08 -0.06 NO3 -N -0.07 (s=.370) (s=.222) (s=.170)
0.03 -0.03 0.11 parameterPO4 -1 (s=.463) (s=.326) (s=.067)
TABLE 5.16 PEARSON'S r BETWEEN FOUR CHEMICAL PARAMETERS AND THE HUMAN FACTORS (WET-SEASON CASES AT THE "VILLAGE LEVEL")
Human Factor
POP PIG POUL
*0.61 -0.26 -0.37 COND (s=.003) (s=.163) (s=.076)
Chemical -0.16 -0.19 -0.20 NH4 -N (s=.256) (s=.236) (s=.224)
-0.02 -0.30 -0.13 NO3 -N (s=.469) (s=.126) (s=.315)
0.23 parameterPO4 -P -0.25 (s=.177) (s=.171) (s=.171) (s=.060)
TABLE 5.17 PEARSON'S r BETWEEN FOUR CHEMICAL PARAMETERS AND THE HUMAN FACTORS (DRY-SEASON CASES AT THE "VILLAGE LEVEL")
Human Factor
POP PIG POUL
*0.56 -0.48 -0.28 COND (s=.008) (s=.035) (s=.158)
Chemical -0.16 -0.18 -0.03 NH4 -N (s=.258) (s=.260) (s=.454) 0.01 -0.31 0.18 NO3 -N (s=.496) (s=.129) (s=.262)
(s=.230) parameter -0.10 -0.21 PO4 -P (s=.076) (s=.343) (s=.343)
NOTE Figures in the brackets are the significance levels. *The correlation coefficients significant at 0.050 level. COND- conductivity
POP- no. of inhabitants PIG- no. of pigs POUL- no. of poultry 72
TABLE 5.18
PARTIAL CORRELATION BETWEEN COND AND POP
(WET-SEASON CASES AT THE "VILLAGE LEVEL")
Control Variable(s) Partial Correlation between COND and POP
PIG 0.60 (s=0.009)
POUL 0.59 (s=0.010)
PIG and POUL 0.59 (s=0.013)
TABLE 5.19
PARTIAL CORRELATION BETWEEN COND AND POP
(DRY-SEASON CASES AT THE VILLAGE LEVEL)
Control Variable (s) Partial Correlation between COND and POP
PIG 0.53 (s=0.025)
POUL 0.52 (s=0.027)
PIG and POUL 0.52 (s=0.033)
NOTE: Figures in the brackets are the significance levels.
COND- conductivity
pop- no. of inhabitants
PIG- no. of pigs
POUL- no. of poultry 73 ductivity, in groundwater. The lack of significant correlation uetween
NH4-N, PO4-P and the independent variables seems to suggest that factors other than those being selected in this study (e.g. landuse) are involved in determining the phosphate and ammonium levels of groundwater. The lack of significant relationship between NO3-N and the independent variables, particularly PIG and POUL, is somewhat surprising. It has not been able
to ascertain whether this is due to denitrification in the groundwater
and more research is needed to resolve the problem.
5.5 Temporal Changes in Groundwater Quality
Groundwater quality does not only varies over space Dui. d15V UVCL
time. This section aims at depicting and explaining seasonal and daily
changes in groundwater quality.
5.5.1 Seasonat Differences in Gnoundwater Quatity
In order to see whether or not groundwater quality in the wet
and dry season is different, a paired t-test was performed for each of
the 25 parameters shown in Table 5.20. Only the data obtained from those
184 wells where water samples were collected both in the wet and dry sea-
son were used.
Results in Table 5.20 indicate that samples collected in the
dry season contained significantly higher levels of Ca, Si02, Zn and Mn,
but lower levels of NO3-N and SO4. No significant difference in the con-
centrations of other chemical constituents can be observed.
Seasonal differences in the quality of groundwater can be
caused by physical as well as human factors. During the summer season,
the relatively lower level of SiO 2 could probably be accounted for by
the dilution effect of the abundant rainfall. On the other hand, the
higher level of NO3-N is likely caused by the flushing effect of the
summer rain. The co-existence of dilution and flushing effects may appear 74
TABLE 5.20
RESULTS OF PAIRED t-TEST OF WET-SEASONAND DRY-SEASON GROUNDWATERQUALITY
Difference between Difference between No. of Mean of Mean of wet and Dry Seasons Significance Level Parameter Wet and Dry Seasons Cases wet-Season (Dry-season minus of Paired t-test Dry-Season (in%) Wet-season) pH 184 6.2 6.4 + 0.2 0.01
K mg/1 181 6.6 5.6 N.S.
Na mg/1 181 22.6 23.3 N.S.
Ca mg/1 181 25.7 27.1 + 1.4 + 5.4 0.01
Mg mg/1 181 6.03 6.19 N.S.
NH4-N mg/1 181 0.26 0.57 N.S.
HCO3 mg/1 184 52.3 51.7 N.S.
Cl mg/1 184 32.0 35.8 N.S.
NO3-N mg/1 184 19.4 13.2 - 6.2 - 32.0 0.01
PO4-P mg/1 181 0.24 0.25 N.S.
SO4 mg/1 184 15.4 13.3 - 2.1 13.6 0.01
Si02 mg/1 181 13.7 14.6 + 0.9 + 6.6 0.01
Zn mg/1 181 0.365 0.620 + 0.255 69.9 0.05
Pb mg/1 181 N.D. N.D.
Fe mg/1 184 0.003 0.002 N.S.
Mn mg/1 184 0.051 0.113 + 0.062 + 121.6 0.05
Ni mg/1 184 0.006 0.002 N.S.
Cd mg/1 184 0.002 0 N.S.
Cr mg/1 184 N.D. N.D.
Cu mg/1 184 0.001 0 N.S.
TH mg/ 1 181 89.0 102.2 + 13.2 + 14.8 0.01
PERNA 181 43.1 40.6 2.5 5.8 0.01
SAR 181 1.13 1.10 N.S.
WrEMP °C 164 27.5 21.0 - 6.5 23.6 0.01
TEMPDIF 0 C 164 3.4 1.8 -.1.6 67 1 0.01
NOTE: N.S.= not significant at 0.05 level SAR= sodium adsorption ratio
N.D.= not detectable WTEMP=groundwater temperature
TH= total hardness TEMPDIF= air temperature- groundwater temperature
PERNA= per cent sodium 75
to be contradictory. However, it should be pointed out that the rate of release of silica is limited by the rate of chemical weathering and is
rather slow whereas the release of NO3-N is rapid and unimpeded owing to
the accumulation of large amount of pig and poultry wastes in the water
courses in the New Territories.
The application of lime to neutralize acidic soils in the
New Territories during the winter season when most farmlands lie fallow
is probably the reason why Ca level is higher in winter. This is also
reflected in the higher average pH value for the winter samples.
No obvious reasons can be used to account for the seasonal
differences in the concentrations of Zn, Mn and SO4. More research is
needed to unravel the causes for such changes.
5.5.2 Day-to-day Changes in Groundwater quatity
Attempts have also been made to investigate the day-to-day
changes of three chemical parameters (conductivity, pH and NO3-N), and
to examine their relationship with the antecedent precipitation index
(API) and the depth of water level from the ground surface (GDEPTH).
API is a measure of the amount of rainfall before the day of
sampling and was derived from the following equation (Gregory Walling,
1973):
APIn =ppt +0.65XAPIn-1
where API n= antecedent precipitation index at day n of a year
API n-1= antecedent precipitation index at day n-1 of a year
ppt= precipitation at day n of a year.
The rainfall records at Fanling Army Depot and Tai Lung Farm (Figure 5.7)
were used for the computation.
GDEPTH was estimated at the time of sampling by counting the
number of cement-rings (Photo 5.1) of fixed length above the water sur- 76
FIGURE 5.7 DAILY FLUCTUATION OF RAINFALL, DEPTH OF WATER LEVEL
FROM GROUND SURFACE (GDEPTH) AND CONCENTRATIONS OF NO3-N
OF THE THREE MONITORING STATIONS. (m m)
20-
40-
Rainfall 60.
80-
100-
station A 120-
station B
station C 140-
160-
180-
(mg/I)
16.0
14.0
NO3-N 12.0
10.0
8.0
6.0
4.0
2.0
DEC JUL AUG SEP 0 CT 0
(m)
1.0
2.0 GDEPTH
3.0.
4.0 77
PHOTO 5.1
CEMENT-RINGS" USED FOR CONSTRUCTION OF THE INNER WALL OF THE WELL 78
face. It is a measure of the relative rise and fall of the water table
and could be an indicator of the dilution effect of rainfall.
Three wells were selected as monitoring stations (Refer to
Figure 3.1 on p.22) where daily water samples were taken. Stations A
and B are located close to each other at Pak Fuk Tsuen and station C at
Ta Shek Wu. These three stations are surrounded by farmland growing
vegetables and flowers. The sampling programme lasted for six months
from 1st of July to 31st of December, 1980 at stations A and B, but only
for three months from 1st of July to 30th of September, 1980 at station C.
Figures 5.7, 5.8 & 5.9 portray the daily fluctuation of
rainfall, GDEPTH, NO3-N concentration, pH and conductivity at the three
monitoring stations respectively. The monthly means of these variables
were also computed and shown in Figure 5.10. From Figures 5.7, 5.8
5.9, it can be seen for stations A and B. the concentrations of NO 3-N,,
like rainfall, are higher in summer than in winter whereas the pH is
higher in winter than in summer. The daily fluctuations of NO3-N con-
centration, ph and conductivity at stations A and B are similar but are
different to that of station C. This suggests that the solute levels at
stations A and B are controlled by the same mechanism because of their
closed locations. On the other hand, water chemistry at station C may
be controlled by other factors. This observation seems to indicate that
the chemistry of well water in different parts of the study area are con-
trolled by different mechanisms and are more complicated than was original-
ly envisaged.
A correlation analysis was carried out to examine the relation-
ship between API, GDEPTH and conductivity, pH and NO3-N concentration. The
results (Table 5.21) indicate that there was no significant correlation
between the three chemical parameters and GDEPTH. Conductivity was not 79
FIGURE 5.8 DAILY FLUCTUATION OF RAINFALL, DEPTH OF WATER LEVEL FROM
GROUND SURFACE (GDEPTH) AND pH OF THE THREE MONITORING
STATIONS.
Cmrn]
20-
40-
Rainfall 60-
80-
100-
station A 120- station B
station C 140-
160-
180-
9.0
pH pH
8.0
7.0
6.0 0 CT N0V DEC JUL AU G SEP
CmJ
gyro
2.0 DEPTH
3.0
4.0 FIGURE 5.9 DAILY FLUCTUATION OF RAINFALL, DEPTH OF WATER LEVEL FROM 80 GROUND SURFACE (GDEPTH) AND CONDUCTIVITY OF THE THREE
MONITORING STATIONS. I I I I Cmm1 j
20-
40-
Rainfall 60-
80-
100-
station A 120- station B
station C 140-
160-
1 8 o
us/cm)
250
Conductivity
210
170
130
90
50 OCT NOV DEC JUL AUG SEP
(m) 1.0
2.0 GDEPTH
3.0
4.0 FIGURE 5.10 81
MONTHLY MEANS OF RAINFALL, CONDUCTIVITY, NOD-N AND pH
OF THE THREE MONITORING STATIONS Monthly Rainfall (mm)
700 651 Conductivity
600 (S/cm) 300
500 250
400 200
303 296 300 150
200 l00
100 50 42 34
0 0 JUL AUG SEP OCT NOV DEC JUL AUG SEP OCT NOV DEC
pH NO3-N (mg/1)
15 8.0
7.5
10 7.0
6.5
6.0 5
5.5
0 5.0 JUL AUG SEP OCT NOV DEC JUL AUG SEP OCT NOV DEC
LEGEND: station A station B
station C * (only the data of the first three months
are available for station C) TABLE 5.21
PEARSON'S r BETWEEN API, GDEPTH AND CHEMICAL PUALITY DATA COLLECTED AT THE THREE MONITORING STATIOS
NO -N pH 3 Condustivity Station Station Station Station Station Station Soation Station Station A B C A B C A B C
*-0.17 *-0.50 *-0.41 *-0.17 *-0.21 0.14 -0.02 -0.14 0.20 (s=.030) (s=.008) (s=.181)
API (s=.030) (s=.001) (s=.001) (s=.816) (s=.086) (s=.056)
0.08 -0.13 0.03 0.11 0.02 0.09 0.05 0.02 0.15 (s=.321) (s=.107) (s=.307) GDEPTH (s=.183) (s=.8.17) (s=.390) (s=.545) (s=.846) (s=.524)
NOTE: Figures in the brackets are the significance level
*The correlation coefficients significant at 0.050 level
API - antecedint precipitation index
GDEPTH - depth of water level from ground surface
82 83 significantly related either to API or GDEPTH. On the other hand, pH was inversely correlated with API at all three stations. This can be explained by the fact that rain water is typically slightly acidic.
The correlation between NO3-N concentration and API were only signifi- cant at stations A and B. The negative sign of the correlation co- efficients indicates that NO3-N levels are slightly lower after long periods of rain. This seems to contradict my earlier deduction that
the higher levels of NO3-N during the summer season were due to the
flushing effects of the rainfall. Considering the different time spans
considered in the previous and this section, the contradiction is more
apparent than real. Whilst NO3-N levels could be generally higher
during the summer season owing to the percolation of NO3-N rich water
from the ground surface to the water table, it could also be lower
during the rainy days of the summer season owing to the dilution effect.
It can be seen from Figure 5.7 that NO3-N concentration at the monitoring
stations dropped at the day of rainfall but rose very rapidly on sub-
sequent days to levels exceeding that of the pre-storm days. However,
it should be admitted that the behaviour of NO3-N, as shown in Figure 5.7,
is very complicated and may not be readily explained by API and GDEPTH.
5.6 Summary
Groundwater in the Fanling-Sheung Shui area is slightly acidic
with Ca and Na as the most abundant cations, and Cl and HCO3 as the most
abundant anions. Heavy metals exhibit the largest amount of variability
and are believed to be derived from a limited number of point sources.
No well defined spatial pattern in groundwater quality can be depicted.
The major cations in the groundwater are contributed by the re-
lease of solutes from chemical weathering of the welded tuff in the study
area. The significant correlation between the conductivity and the number 84
of inhabitants suggests that the overall solute levels in groundwater are also determined by contaminants of anthropogenic origin.
Levels of nitrate higher than the recommended limit for drinking were detected in over half of the water samples, suggesting health risk could arise from using groundwater for drinking purpose. Although no case of methaemoglobinaemia has been reported, it is necessary to caution the inhabitants in the study area of such risks. 85
CHAPTER 6
PERCEPTION OF GROUNDWATER QUALITY BY THE WELL USERS
In the preceding two chapters, it has been mentioned that ground- water is not the only source of drinking water in the study area. Nearly
40% of the well users had more than one type of drinking water supply.
Their choice for a particular use of water is believed to be partly determined by their perception of the cleanliness of that water resource.
As the groundwater in the study area contains excessive amounts of NO3-N
and NH4-N, people using this water for drinking purpose are likely to be
subjected to some adverse health effects.
This chapter attempts to determine users' level of concern for
groundwater pollution in the study area and to examine the factors which
may affect their concern. Attempts have also been made to investigate
the users' perception of groundwater quality and the discrepancy between
the perceived and actual quality of the groundwater. The incongruity
between perception and action will also be discussed.
The data were obtained by face-to-face interview with 187 well
users whose wells were sampled during the period from December 29, 1980
to January 4, 1981.
6.1 Well Users' Concern of Groundwater Pollution
Figure 6.1 portrays a conceptual moael ror the percepLlor1 01
water pollution. It shows the possible factors which may affect people's
perceived quality of a water body. These factors can be classified into
two main groups, namely, environmental components and personal components. FIGURE 6.1
CONCEPTUAL MODEL FOR THE PERCEPTION STUDY OF WATER POLLUTION
NVIRONMENTAL COMPONENTS
Characteristics of surrounding area (e.g. types of land- use nearby, relief, rock types, etc.)
Physical, chemical, biological and hydrological PERCEPTION BEHAVIOUR
characteristics of water body Perceived Preferences attributes and attitudes Uses made of water toward water of water body body body
Observer's personality characteristics (e.g. past experience, values, disposition, etc.)
)server's socio-economic characteristics (e.g. sex, age, occupation, income, education level, length of residence, etc.) PERSONAL COMPONENTS 86 87
People's behaviour towards and use of any water resource are directly determined by their perceived attributes of that resource.
In the study of environmental perception, people's concern about pollution is always the first thing to be studied. This is important because the level of concern may in turn influence their choice and uses made of the water source. In order to find out the factors affecting well users' level of concern of groundwater pollution, two indiced were
constructed, namely the concern index and pollution index.
For each respondent, a concern index was calculated, based on his
responses to certain relevant questions (Table 6.1). The frequency dis-
tribution of the concern index is presented in Figure 6.2. For each
water sample, a pollution index was also calculated, based on the amount
of each chemical pollutant in excess of the maximum limit of that con-
stituent for drinking purpose and the relative effects of these pollutants
on human health. According to their effects on human health, the chemical
parameters are divided into four categories:
category 1- those with serious health effect (Cd, Cr, Pb, NO3-Nf. NH4-N)
category 2- those with slight health effect (Zn, SO4, Mg)
category 3- those will cause domestic troubles but have no known health effect (pH, HCO3, Cl, Cu, Fe, Mn, Ca, Ni, PO4-P)
category 4- those will not cause domestic troubles and
have no known health effect (K, Na, SiO2)
To calculate the pollution index, different weightings were given to
different categories of pollutants.- For example, a factor of 3 was given
to category 1, 2 to category 2, 1 for 3 and 0 for 4. If a pollutant of
category 1 exceeds 4 times of the standard, for example, then the score
for that pollutant would be 3 X 4= 12. For each water sample, the
scores for individual pollutants were summed up to give the pollution
index. 88
TABLE 6.1
CALCULATION OF CONCERN INDEX
Question Score allocated
No score for category of no Q.25 whether or not respondent recog- 1 score for category of yes nize that groundwater in the
New Territories is polluted.
Q.26 indicators used to identify No score for category of don't know 1 score for other categories groundwater pollution.
No score for category of don't know Q.27 whether or not groundwater pollution exists in the 1 score for category of probably yes
study area. or probably not 2 scores for category of "certainly yes" or certainly not
Q.29 user's perceived quality of the No score for category of don't know groundwater in his/her own or refuse to answer 1 score for category of probably well. polluted or probably unpolluted 2 scores for category of definitely
polluted or "definitely unpolluted"
No score for category of don't know' Q.32 sources of the pollutants. 1 score for other categories
No score for category of no Q.34 whether have complaint to the 1 score for category of yes authorities concerning the
groundwater pollution.
No score for category of no Q.36 any action taken to tackle the 1 score for other categories problem of polluted ground- water.
No score for category of don't know Q.37 any action taken if the ground- or impossible water is proved to be polluted. 1 score for other categories
concern index= total scores obtained (minimum= 0 maximum= 9) 89
FIGURE 6.2
FREQUENCY DISTRIBUTION OF THE CONCERN INDEX (n=187)
0 10 20 30 40 50 60 70 80 of cases
0 no case (NOT CONCERNED)
1- 3 34 (SLIGHTLY CONCERNED)
(MODERATELY CONCERNED) 4- 6 119
Scores 7- 9 34 (HIGHLY CONCERNED)
LEVEL OF CONCERN
FIGURE 6.3
FREQUENCY DISTRIBUTION OF THE POLLUTION INDEX (n=134)
of cases 0 10 20 30 40 5O 60 70 80
0- 10 47 (UNPOLLUTED)
(SLIGHTLY POLLUTED) 11- 30 102
(MODERATELY POLLUTED) 31- 50 2n scores
>50 15 (HIGHLY POLLUTED)
LEVEL OF POLLUTION 90
Frequency distribution of the pollution index is presented in
Figure 6.3. The results show that most of the well users in the Fanling-
Sheung Shui area are moderately concerned with the problem of groundwater pollution.
Studies carried out overseas indicate that the level of concern
about pollution is positively related to the level of exposure to the
pollutant, but is not necessarily related to social characteristics of
the respondents (Cutter, 1981). In order to investigate the factors that
may affect users' level of concern of groundwater pollution, the relation-
ships between the level of concern and some environmental and socio-
economic factors were measured.
Since most of the variables included in the analysis possess either
nominal or. ordinal properties (Table 6.2), the analysis of the relationships
between independent and dependent variables is based largely on nonpara-
metric statistics. The coefficient of contingency (C) was used to measure
relationships between nominal variables. Where one variable is nominal
and the other ordinal, the Mann-Whitney U test (Taylor and Hall, 1977) is
the most appropriate statistics to ise._ However, it is not available in
the Statistical Package for the Social Sciences (SPSS), thus the co-
efficient of contingency had to be used in its place. In cases where
both variables were ordinal, Kendall's tau b or tau c was calculated as
a measure of the degree of relationship. Chi-square statistics were also
computed to test the statistical significance of the measured relation-
ships and in some cases to determine whether or not the variables are
statistically independent. It must be borne in mind that Kendall's tau
and the coefficient of contingency are nonprobability statistics which
can be compared only to themselves. They are even incomparable when the
tables are of unequal size. 91
TABLE 6.2
MEASUREMENT SCALES FOR VARIABLES IN THE ANALYSIS
Variable Measurement Scale
Independent Variables:
(i) Socio-economic components-
1. sex nominal ordinal 2. age (in groups) 3. education level ordinal 4. occupation nominal
5. income (in groups) ordinal 6. length of residence (in groups) ordinal 7. ownership of the well nominal
8. whether respondent uses groundwater for drinking purpose or not nominal 9. whether respondent recognized the
problem of groundwater pollution in the New Territories or not nominal
(ii) Environmental components-
1. types of land use nominal 2. smell nominal 3. colour nominal 4. turbidity nominal 5. pollution index (level of chemical ratio and ordinal pollution) 6. pollution sources exist nearby
or not nominal
Dependent Variables:
1. 1 evel of concern ratio and ordinal
2. user's perceived cleanliness of the
three water sources nominal
3. user's perceived cleanliness of the groundwater he/she uses ordinal
4. categories of discrepancy between the
perceived and actual groundwater quality- under-estimated, about
right and over-estimated ordinal 92
Table 6.3 presents results of the statistical relationships between level of concern and certain environmental and socio-economic factors. Only 3 of the 14 factors show significant but rather weak relationship with the level of concern. Man is found more concerned with groundwater pollution than woman (Table 6.4). Smell from ground-
water also contributes to the users' higher level of concern (Table 6.5).
Moreover, there is a positive but rather weak relationship between the
respondent's level of concern and his family monthly income. No
significant relationship between level of groundwater pollution and
level of concern of the user. This may be explained by the fact that
the deterioration of chemical quality of the groundwater can hardly be
perceived and its effects are also unfamiliar to the well users. This
lack of significant relationships precludes any further attempt to
evaluate the relative importance of the environmental and socio-economic
factors in determining the level of concern.
6.2 Perception of Groundwater Quality by the Well Users
6.2.1 Comparison of the perceived Degree if Cteantiness between
Gkoundwater, Tap water and Stream Water
As mentioned in the introduction of this cnapter, uuun LcN
water and groundwater are available to nearly 40% of the well users in
the study area. The cleanliness of the water sources as perceived by
the user is one of the factors which affect user's choice of water.
Therefore, comparison of the degrees of perceived cleanliness between
groundwater, tap water and stream water was made in order to find out
which water source is considered as the cleanest by the well users.
This was estimated by the method of paired comparison (Mun and Yau,
1979), which takes into account not only the first rank figures but also
the second and third rank values. The procedures and results of calcu- 93
TABLE 6.3
COEFFICIENTS OF CONTINGENCY AND KENDALL'S TAU C FOR MEASUKINV
THE RELATIONSHIP BETWEEN LEVEL OF CONCERN AND SOME SOCIO-
ECONOMIC AND ENVIRONMENTAL FACTORS
Dependent variable= level of concern (ordinal scale)
Statistics used for
Measure- the measure of re- Signifi- Independent ment lationship between cance variable scale dependent and inde- level pendent variables
C= 0.196 *(0.707) 0.020 sex nominal
ordinal tau c N.S. age (in groups) N.S. education level ordinal tau c
C N.S. occupation nominal
ordinal tau c= 0.126 0.020 income (in groups) tau c N.S. length of residence (in groups) ordinal N.S. ownership of the well nominal C
whether respondent uses ground- N.S. water for drinking purpose or nominal C
not N. S. types of land use nominal C C= 0.294 *(0.707) 0.001 smell nominal C N.S. colour nominal
C N.S. turbidity nominal N.S. ordinal tau c level of pollution
pollution sources exist nearby N.S. nominal C or not
NOTE: C= the coefficient of contingency tau c= Kendall's tau c Only the coefficients significant at 0.050 level or above are shown. *The figure shown in the brackets is the upper limit of the coefficient of contingency. It is calculated by (k-1)/k where the k is equal to the smaller number of rows or columns of the table. 94
TABLE 6.4
CROSS-TABULATION OF LEVEL OF CONCERN BY SEX
Frequency Level of Concern ow%) Slightly Moderately Highly Category concerned concerned concerned
Male 11.9 65.3 22.8 (n=l0l)
Female 25.6 61.6 12.8 Respondent's (n=86)
Sex
TABLE 6.5
CROSS-TABULATION OF LEVEL OF CONCERN BY SMELL
Level of Concern Frequency (row%) Slightly Moderately Highly concerned concerned concerned Category
With smell 0 16.7 83.3 (n=6)
Smell 18.8 65.2 16.0 No smell
of (n=181) Groundwater 95
lation are listed in Tables 6.6, 6.7 & 6.8.
It was found that groundwater got the highest score (1.88)
followed very closely by tap water (1.86). Stream water got the lowest
score (0.76) reflecting the very serious level of pollution in streams
of the study area. Results of X2-test also show significant differences
in the perceived cleanliness between these three types of water sources
(p= 0.001).
The observation that groundwater is regarded as the cleanest
is also reflected by the fact that in those villages where tap water is
available, some well users still prefer to use groundwater as drinking
water. Moreover, over half (51.3%) of the well users who are using
groundwater for drinking purpose state that they would continue to do so
even if tap water is supplied to their dwelling units. 18% of the house-
holds insist that they will not find other water sources even if the ground-
water is proved to be chemically contaminated
In order to find out whether respondents' rankings are related
to their socio-economic background, some nonparametric statistical tests
were carried out (Table 6.9). Among the twelve factors considered, only
two of them exhibit statistically significant yet rather weak relationship
with the dependent variable. These are respondent's education level and
user's perceived cleanliness of the groundwater. The lack of strong re-
lationships between the dependent and independent variables probably arise
from the deep-rooted Chinese traditional belief that the groundwater tastes
sweet and is clean.
The relationship between the dependent variable and the educat-
ion background of the respondents was further assessed by a X2-test. Sign-
ificant differences are revealed (p= 0.013) indicating that the higher the
education level, the more likely would be the respondent to regard tap
water as the cleanest (Table 6.10). 96
TABLE 6.6 RESPONDENTS' RANKING OF CLEANLINESS AMONG THREE TYPES OF
WATER SOURCES
No. of Respondents TvDe of Water Source lst rank 2nd rank 3rd rank
Groundwater 82 (43.9%) 93 (49.7%) 12 (6.4%)
Tap Water 93 (49.7%) 70 (37.4%) 24 (12.9%)
Stream Water 12 (6.4%) 24 (12.9%) 151 (80.7%)
Total 187 (100.0%) 187 (100.0%) 187 (100.0%)
TABLE 6.7 NUMBER OF RESPONDENTS WHO PERCEIVE THAT WATER SOURCE i
IS CLEANER THAN WATER SOURCE j
Water Source 1 Groundwater Tap Water Stream Water
Water Source j
Groundwater 97 19
Tap Water 90 29
Stream Water 168 158
PERCENTAGE OF RESPONDENTS WHO PERCEIVE THAT WATER SOURCE i TABLE 6.8
IS CLEANER THAN WATER SOURCE j
Water Source i Groundwater Tap Water Stream Water
I Water Source j
10.50 0.52 0.10 Groundwater
0.50 0.16 Tap Water 0.48 k0.50 Stream Water 0.90 0.84
1.86 0.76 Total 1.88
100 9.
Total No. of Respondents
110.50 will be given if comparison is macte netween Scuitu Lype UL WQL-GL vliL 97
TABLE 6.9
COEFFICIENTS OF CONTINGENCY FOR MEASURING THE RELATIONSHIP
BETWEEN USER'S PERCEIVED CLEANLINESS OF THREE WATER SOURCES
AND SOME SOCIO-ECONOMIC AND ENVIRONMENTAL FACTORS
Dependent variable= user's perceived cleanliness of three water sources - groundwater, tap water and stream water (nominal scale)
Statistics used for
Measure- the measure of re- Signifi- Independent ment lationship between cance variable scale dependent and inde- level pendent variables
sex nominal C N.S.
C N.S. age (in groups) ordinal C= 0.282 *(0.816) education level ordinal 0.013
N.S. occupation nominal C
C N.S. income (in groups) ordinal N.S. length of residence (in groups) ordinal C
ownership of the well nominal C N.S.
whether respondent uses ground- water for drinking purpose or nominal C N.S. not
whether respondent recognized
the problem of groundwater nominal C N.S. pollution in the New Territories or not
N.S. level of concern ordinal C
user's perceived cleanliness C= 0.367 *(0.816) 0.001 of the groundwater he/she ordinal uses
pollution sources exist nearby nominal C N.S. or not
NOTE: C= the coefficient of contingency Only the coefficients significant at 0.050 level or above are shown. *The figure shown in the brackets is the upper limit of the coefficient of contingency. It is calculated by (k-l)/k where the k is equal to the smaller number of rows or columns of the table. 98
TABLE 6.10
CROSS-TABULATION OF RANKING OF CLEANLINESS BY EDUCATION LEVEL
Frequency Water Source Ranked Cleanest (row %) Groundwater Tap water Stream water ranked the ranked the ranked the cleanest Category cleanest cleanest
No formal education 52.5 39.0 8.5 (n=118)
Primary 4.2 education 37.5 58.3 Education (n=48)
Secondary 0 Level education 19.0 81.0
in=21)
X2-test: p= 0.013
TABLE 6.11
RESPONDENTS' PERCEIVED QUALITY-OF-THE GROUNDWATER THEY USE
No. of Respondents Frequency(%) Category
0 Refuse to answer 0
3.2 Don't know 6
20 10.7 Definitely polluted.
22 11.8 Probably polluted
9.1 Probably unpolluted 17
65.2 Definitely unpolluted 122
L87 100.0 Total 99
6.2.2 Well Users'Perceived Cteantiness of Groundwater of their own
Wetts
As shown in Table 6 .61 nearly nal or Lrle well users regard
groundwater as the cleanest of all available water sources. It is in-
teresting to investigate how well users perceive the quality of the
groundwater of their own wells and what factors affect their perception.
The data from the questionnaire survery confirm that the
majority of the respondents (65.2%) regard the groundwater they use is
definitely unpolluted. Only 10.7% of the well users assert that the
groundwater is definitely polluted (Table 6.11). According to their
perception of the cleanliness of groundwater, the well users were sub-
divided into four groups. Group 1 are those who regard groundwater as
definitely polluted, group 2 probably polluted, group 3 probably un-
polluted and group 4 definitely unpolluted. Based on these ranking,
coefficients of contingency and Kendall's tau c were calculated to
measure the relationships between users' perceived cleanliness of ground-
water and some environmental and socio-economic factors (Table 6.12).
Significant and relatively_ strong relationships are found
between the users' perceived cleanliness and factors such as whether
respondent uses groundwater for drinking purpose or not, smell,
colour and turbidity. Also, results of X2-test (Table 6.13) reveal
significant differences in the rating of groundwater quality between the
respondents who still use the groundwater for drinking purpose and the
respondents who do not (p= 0.001). The percentage of respondents who
perceive their groundwater as definitely unpolluted or probably
unpolluted (as opposed to definitely polluted or probably polluted)
is much higher among those who still use groundwater for drinking purpose
than those who do not (Table 6.13). 100
TABLE 6.12
COEFFICIENTS OF CONTINGENCY AND KENDALL'S TAU C FOR MEASURING
THE RELATIONSHIP BETWEEN USERS' PERCEIVED CLEANLINESS
OF THE GROUNDWATER THEY USE AND SOME QUALITY
AND SOCIO-ECONOMIC FACTORS
Dependent variable= users' perceived cleanliness of the groundwater they use (ordinal scale)
Statistics used for Measure- the measure of re- Signifi- Independent ment lationship between cance variable scale dependent and inde- level pendent variables
sex nominal C N.S.
age (in groups) ordinal tau c= 0.131 0.005
education level ordinal tau c= -0.105 0.010
occupation nominal C N.S.
income (in groups) ordinal tau c N.S.
length of residence (in groups) ordinal tau c N.S.
ownership of the well nominal C N.S.
whether respondent uses ground- C= 0.363 *(0.866) water for drinking purpose or nominal 0.001 not
pollution sources exist nearby nominal C N.S. or not
whether respondent recognized
the problem of groundwater nominal C N.S. pollution in the New Territories or not
C 0.346 *(0.894) smell nominal 0.001
C= 0.342 *(0.707) co lour nominal 0.001
C= 0.331 *(0.707) turbidity nominal 0.001
tau c= -0.109 level of concern ordinal 0.020
nr inal tau c N.S. level of pollution
NOTE: C= the coefficient of contingency tau c= Kendall's tau c Only the coefficients significant at 0.050 level or above are shown. *The figure shown in the brackets is the upper limit of the coefficient of contingency. It is calculated by (k-l)/k where the k is equal to the smaller number of rows or columns of the table. 101
ABLE 6.13
CROSS-TABULATLON OF "RESPONDENTS' PERCEIVED ELEANLINESS OF THE
GROUNDWAYER THEY USE" BY THREE SENSIBLE QUALITY PARAMETERS -
SMELL", "COLOUR" & "TURBLDITY" AMD " AND "WHEYHER OR NOT THE
RESPONDENT USES GROUNDWATER FOR DRINKING PURPOSE"
Frequency Perceived Cleanliness
(row %) Definitely of Defnitely of probably probably
polluted unpolluted Category
Smelly 100.0 0 (n=6)
Smell No smell 20.6 79.4 (n=175) of Groundwater
Coloured 60.0 40.0 (n=15)
Colour Colourless 19.9 80.1 (n=166) of Groundwater
Turbid 50.0 50.0 (n=26)
Turbidity Clear 18.7 81.3 (n=155)
of Groundwater
Yes for (n=133) 15.8 84.2
Use Np 43.8 56.2 (n=48) drinking of groundwater
2 -test: p = 0.001 X 102
Significant differences are also found between the users'
rating of quality of the groundwater and the three sensible quality parameters (Table 6.13). X2-tests show that these three are all signi- ficant at 0.001 level. It can be seen from Table 6.13 that well users are more likely to regard their groundwater as definitely polluted or probably polluted if the water is smelly, coloured or turbid. These are visible or tangible properties and are probably the indicators which users would use to evaluate groundwater quality.
6.2.3 Indicatons used identify gnoundwater pottution by the wett Users
As elucidated in the preceding section, significant relation- ships are found between the user's perception of groundwater quality and three sensible quality parameters- smell, colour and turbidity. These findings are consistent with many studies undertaken overseas (David, 1971
Ditton Goodale, 1973 Akintola et al., 1980).
In the present study, respondents were also asked how they would identify water pollution, and the indicators commonly used are listed in Table 6.14. The data were obtained from an open-ended question and the sequence of the answers given is also taken into account by giving a weighting factor to the indicators. For example, the first answer given will be given 5 scores, the second 4 and so on. Therefore, only 1 score will be given for the fifth answer. After that, the total scores for each indicator were summed up and then the relative importance between indicators can be evaluated by the total scores that each indicator obtained. It was found in Table 6.14 that turbidity, the existence or otherwise of nearby pollution sources, the smell, dirt and colour in the well water are the five indicators most frequently mentioned. This accords with an earlier deduction that the local well users employed visible or tangible characteristics to assess the water quality. 103
TABLE 6.14
INDICATORS COMMONLY USED BY RESPONDENTS FOR EVALUATING
THE GROUNDWATER QUALITY
Category Score Computed
Turbidity 324
Existence or otherwise of 263 nearby pollution sources
Smell 148
Dirt in the well water 100
Colour 94
*Other categories mentioned including (in descending order of score computed)- muddy bed of the well, sandworm existed, bacteria existed, low relief, oil spill, without maintenance, render illness after consumption, algae existed, small depth of the well, moss existed, insect existed, sunlight cannot
reach the water surface, unusual temperature, drinking purpose is prohibited by the government, cause the death of fish, near the sea, cannot used for production of sprouted broad bean, chemical substance existed, small amount of water and not sweet.
TABLE 6.15
FREQUENCY DISTRIBUTION OF THE THREE CATEGORIES OF DISCREPANCY
BETWEEN ACTUAL AND PERCEIVED GROUNDWATER QUALITY
Category of Discrepancy No. of Cases (n=181)
under-estimation of the level of pollution 101 (55.8%)
about-right assessment of the level of 53 (29.3%) pollution
over-estimation of the level of pollution 27 (14.9%) 104
6.2.4 Discrepancy between Actuat and Perceived Gnoundwater Quatity
Some studies report that people are able to perceive water pollution, and that their perceptions are reasonably consistent with
scientific measurements of chemical, biological and physical properties of the water body observed (Coughlin, 1976). This section attempts to investigate whether or not such observation can be applied to the well users in the Fanling-Sheung Shui area. This was accomplished by comparing the actual quality, as represented by the pollution index, and the well users' rating quality of the groundwater. The discrepancies can be generalized into three categories- under-estimation, about-right
assessment and over-estimation of the pollution level as shown in
Figure 6.4. Frequency distribution of these three categories of discre- pancy are presented in Table 6.15. It is found that over half of the respondents have under-estimated the level of pollution and only 29.3% of the assessments could be considered as about right. Only a very small percentage of the respondents have over-estimated the pollution level.
Furthermore, the coefficients of contingency shown in Table
6.16 exhibit that significant relationships are found between the variable of discrepancy and the factors such as occupation, education level, whether respondent uses groundwater for drinking purpose or not, level of concern of groundwater pollution, turbidity, colour and whether
respondent recognized the problem of groundwater pollution in the New
Territories or not. The first four factors show relatively strong re- lationships with the variable of discrepancy, and therefore were cross- tabulated with the categories of discrepancy respectively for further
interpretation (Tables 6.17 6.18).
Table 6.17 indicates that respondents who still use ground- water for drinking purpose are more likely to under-estimate the pollution
level. Moreover, less educated people also have a greater tendency to 105
FIGURE 6.4
CATEGORIES OF DISCREPANCY BETWEEN THE ACTUAL AND PERCEIVED
GROUNDWATER QUALITY
User's Rating of Groundwater Quality
Definitely Probably Probably Definitely Polluted Polluted Unpolluted Unpolluted
Highly Polluted
Actual Moderately Polluted
Slightly pollution Polluted
Level
Unpolluted
LEGEND
Symbol Category of Discrepancy
under-estimation of the pollution level
about-right assessment of the pollution level
over-estimation of the pollution level 106
TABLE 6.16
COEFFICIENTS OF CONTINGENCY AND KENDALL'S TAU C FOR MEASURING
THE RELATIONSHIP BETWEEN CATEGORIES OF DISCREPANCY AND
SOME SOCIO-ECONOMIC AND ENVIRONMENTAL FACTORS
Dependent variable= categories of discrepancy between perceived and actual groundwater quality- under-estimated, about right assessed and over-estimated (ordinal scale)
Statistics used for Measure- signifi- Independent the measure of re- ment lationship between cance variable scale dependent and inde- level pendent variables
sex nominal C N.S.
age (in groups) ordinal tau c= -0.114 0.024
education level ordinal tau c= 0.148 0.013
occupation nominal C= 0.462 *(0.866) 0.004
income: (in groups) ordinal tau c N.S.
length of residence (in groups) ordinal tau c N.S.
ownership of the well nominal C N.S.
whether respondent uses ground- water for drinking purpose or nominal C= 0.356 *(0.707) 0.001 not
smell nominal C N.S.
colour nominal C= 0.253 *(0.707) 0.005
turbidity nominal C= 0.284 *(0.707) 0.001
pollution sources exist nearby nominal C N.S. or not
whether respondent recognized
the problem of groundwater nominal C= 0.226 *(0.707) n_niR pollution in the New Territories or not
level of concern ordinal tau c= 0.162 0.002
NOTE: C= the coefficient of contingency tau c= Kendall's tau c Only the coefficients significant at 0.050 level or above are shown. *The figure shown in the brackets is the upper limit of the coefficient of contingency. It is calculated by (k-l)/k where the k is equal to the smaller number of rows or columns of the table. 167
TABLE 6.17
CROSS-TABULATION OF CATEGORIES OF DISCREPANCY BY FARMER.
WHETHER OR NOT THE RESPONDENT USES GROUNDWATER FOR DRINKING PURPOSE
AND EDUCATION LEVEL
Frequency Category of Discrepancy (row%) Under-estimation About-right Over-estimation
of the pollution assessment of the of the pollution Category level pollution level level
Yes 57.7 29.7 12.6 (n=lll)
Farmer No 52.8 28.6 18.6 (n=70)
for Yes 62.4 29.3 8.3 (n=133) Use
of No 37.5 29.2 33.3 groundwaterdrinking(n=48)
No formal
education 62.0 26.5 11.5 (n=113) Level
of Primary education 46.8 36.2 17.0 (n=47)
Secondary education 42.8 28.6 28.6 education (n=21) 108
TABLE 6.18
CROSS-TABULATION OF CATEGORIES OF DISCREPANCY BY
LEVEL OF CONCERN OF GROUNDWATER POLLUTION
Frequency Category of Discrepancy (row%) Under-estimation About-right Over-estimation
of the pollutior assessment of the of the pollution Category level pollution level level
Tightly
concerned 53.3 40.0 6.7 Level (n=30)
of Moderately
concerned 61.5 27.4 11.1 (n=117)
Highly Concern concerned 38.2 26.5 35.3 (n=34) 109 under-estimate the pollution level. It is because that the, caules of groundwater pollution or its effects are not known and understood by them. This can be further supported by the fact that respondents who are highly concerned with groundwater pollution are less likely to under- estimate the level of pollution.(Table 6.18)
6.3 Adaptative Behaviour towards Groundwater Pollution
Users' behaviour towards groundwater, such as the uses made of it and the measures taken to tackle the pollution problem, is affected by their perception of its quality (Refer to Figure 6.1 on p.86). This section attempts to find out what levels of action will be taken by the users who rate the degree of cleanliness differently.
Kendall's tau c was used to measure the relationship between the level of pollution and the level of concern of groundwater pollution and respondents' perceived cleanliness of groundwater(Tables 6.3 6.12).
But no significant relationship can be found. Therefore, this section only focusses on how the level of action is determined by the level of concern and respondents' rating of the quality of the groundwater.
Table 6.19 explains how the action index is constructed and Table 6.20 shows the results. Kendall's tau statistics was again used, but no signi- ficant relationship was found. X2-test also shows no significant differ- ences in level of action among different categories of the two independent variables (Table 6.20).
These findings are contrary to the popular belief that people who have higher levels of concern of groundwater pollution or who regard the environment as more polluted are-more likely to take action. This highlights an important area for future research so that the incongruity between the people's concern for and appraisal of water pollution, and their action could be better understood. 110
TABLE 6.19
CALCULATION OF ACTION INDEX
Question Score allocated
Q.9 apply for tap water. No score for category of no 1 score for category of yes
Q.13 remain to use groundwater for No score for categories of yes,
drinking purpose when tap can't tell or don't know water is available. 1 score for other categories
Q.18 use the groundwater for drinking No score for categories of yes,
purpose again when tap water probably yes or don't know supply is rationed. 1 score for category of no
Q.34 complain to the authorities of No score for category of no 1 score for category of yes groundwater pollution.
No score for category of no Q.36 pretreatments of the polluted groundwater. 1 score for other categories
Q.37 effort made if the groundwater No score for categories of don't know they use is proved to be or continue to use polluted. 1 score for other categories
Action Index= sum of scores of all the questions listed above (minimum= 0 maximum= 4) *More scores are obtained. hiher level of action will be 111
TABLE 6.20
CROSS-TABULATION OF LEVEL OF ACTION BY
LEVEL OF CONCERN OF GROUNDWATER POLLUTION AND
RESPONDENTS' PERCEIVED CLEANLINESS OF THE GROUNDWATER THEY USE
Frequency (row%) Level of Action (Scores)
Category 0 1 2 3
Definitely
polluted 0 45.0 50.0 5.0 (n=20) of Probably
the polluted 0 63.6 18.2 18.2 Perceived (n=22)
Probably
unpolluted 17.6 35.3 29.5 17.6 (n=17)
cleanlinessgroundwaterDefinitely unpolluted 14.7 53.3 24.6 7.4 (n=122)
Not concerned of 0 C) 0 0 (n=O)
Slightly concerned 29.5 44.1 2.9 23.5 (n=34) Level
Moderately concerned of groundwater 9.2 56.4 25.2 9.2 (n=119)
Highly concerned 0 52.9 35.3 11.8 (n=34) concern pollution 112
6.4 Discussion of Results
Most of the well users in the Fanling-Sheung Shui area are moderately concerned about the problem of groundwater pollution, but cannot correctly assess the quality of the groundwater they use. Over half of them have under-estimated the pollution level in their wells.
This finding is not consistent with Coughlin's (1976) statement that people are able to perceive water pollution, and that their perceptions are reasonably consistent with scientific measurements of chemical, biological and physical properties of the water body observed. This can be explained partly by the fact that, unlike other water bodies, ground- water always look clean and tastes sweet. But in actual fact, the chemi- cal pollutants in groundwater are not visible. People who rely on visible or tangible characteristics to evaluate water quality would inevitably make biased judgements.
Furthermore, no relationship can be found between the perceived degree of groundwater quality and level of action in this study. How-
ever, some of the well users did take some actions to tackle the problem such as complaints to the authorities, application for tap water supply and pretreatment of the groundwater before consumption. 113
CHAPTER 7
SUMMARY AND CONCLUSION
7.1 Introduction
The main objectives of this thesis has been to investigate the chemical quality of groundwater in the Fanling-Sheung Shui area to ex- amine its spatial and temporal variations and to study the local well users' perception of groundwater pollution and the discrepancy between the perceived and actual quality of the groundwater. It is hoped that findings of this study may have relevance for evaluating the potential health risk arising from groundwater consumption and understanding the people's choice of water resources. This chapter has, therefore, two major emphases. The first summarizes the major findings, and the second examines the significance of these findings in the context of local water supply.
7.2 Summary of Findings
Groundwater in the Fanling-Sheung Shui area is slightly acidic with Ca and Na as the most abundant cations, and Cl and HCO3 as the most abundant anions. Heavy metals like Cd and Cu are only detected in very few samples and are believed to be derived from localized point sources.
No distinct pattern of spatial variation in groundwater quality can be found. Stability field analysis of the ionic composition of the ground- water indicates that the major cations are mainly controlled by the chemi- cal weathering of fine welded tuff in the study area. However, the signi- ficant correlation found between the conductivity of groundwater and the 114
number of inhabitants in each village also suggests that the overall
solute levels in groundwater may be influenced by the level of human activities.
24 out of the 81 villages investigated were not adequately
served by metered water supply or public standpipes. Of the 187 res- pondents, only 32.6% had tap water supplied to their premises whereas the
rest had to rely on wells (61.0%), public standpipes (2.1%) or nearby
streams (4.3%). Groundwater was mainly used for drinking, bathing,
irrigation, stock rearing, laundry and other washing purposes. Com- parison of the groundwater quality with the water quality standards
indicates that the groundwater in the study area is generally suitable
for uses such as irrigation and livestock rearing but not for human
drinking purposes. Although no case of methaemoglobinaemia caused by
excessive amount of nitrates or illness attributed to high levels of
heavy metals could be confirmed, the potential health risks arising from
the consumption of polluted groundwater do exist. This should not be
taken too lightly because results show that most of the well users hold
a strong positive bias towards the quality of the groundwater they use.
81.8% of the respondents are moderately or highly concerned about
the problem of groundwater pollution, but the level of concern was not
significantly related to the commonly used socio-economic variables.
Results of this study also suggest that groundwater is regarded as the
cleanest of the three water resources (namely groundwater, tap water,
and stream water) followed very closely by tap water. Furthermore, the
users' rating of the groundwater quality was found to rely heavily on
the visible and tangible indicators such as turbidity, smell, colour,
litter and the existence of nearby pollution sources.
Comparison of the actual and oerceived quality indicates that
only 29.3% of the users can correctly assess the quality of the ground- 115 water, and the majority have under-estimated the level of pollution.
Such phenomenon is especially common among the well users who still
use groundwater for drinking purpose. This may be explained by the
fact that the chemical pollutants in the groundwater are invisible
and intangible, and for those people who have no water source other
than groundwater, they have to put up with whatever is available.
7.3 Discussion of the Findings
There are two reasons why a large number of well users in the
Fanling-Sheung Shui area are still using groundwater as the drinking
water. Firstly, groundwater is the only source of water in many remote
villages because tap water is not available. Secondly, most of the well
users hold a biased view against other water sources. Among those res-
pondents who have wells as well as tap water supply, 79% still use ground-
water for drinking purpose.
Unfortunately, the problems of groundwater pollution and its
associated adverse health effects are not familiar to many users. The
pretreatment of groundwater is not widely practised. Even if it is pract-
ised, it is not very useful because boiling and precipitation can only
kill bacteria and remove suspended solids they cannot remove the chemical
constituents, particularly nitrate. The grave situation is likely to
deteriorate further in the near future as a consequence of the rapid
increase in population, cottage industries and the use of chemical fert-
ilizers in the study area. It is imperative that the authority should
caution, by way of mass media, the well users of the nature and extent
of groundwater pollution, and also of the potential health risks arising
from drinking such groundwater. At the same time, the government should
accelerate the supplying of piped water to the remote communities in the 116
New Territories. Research similar to this study should also carried out in other areas where the use of groundwater is popular, such as in Yuen
Long, Ping Shan, Kam Tin and in many remote villages near the northern boundary (Refer to Figure 1.1 on p.4). Further studies should include
the chemical as well as bacteriological aspects of the groundwater quality.
Since perception of water pollution is a central consideration in the choice of water sources, the perception aspect of research should also be strenthened. To rely solely on objective chemical measurements is not sufficient for understanding the effects of water quality on the well users. Any attempt to formulate water supply management strategies without giving due consideration to the perception of the user is likely
to court frustration and failure. 117
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