Domestic Water Consumption in Chennai
Findings of A Sample Survey*
A.Vaidyanathan**
J Saravanan***
Introduction
Most discussions of urban water supply focus on the ability of the public system to provide
certain norms in terms of per capita supply, and various technical, managerial and financial
problems of its operation. However, the public system is not the only source of supply. Some
years back, a large scale survey of Chennai Corporation showed that the total volume consumed
per capita was considerably less than the norm of 120 lpcd considered necessary in metropolitan
areas and that public sources contributed less than half of the total consumption. That
groundwater extracted by privately owned wells and bore wells was the main private source and
that groundwater levels in the city have been falling progressively was known in a general way.
But no hard data were available. The present survey is designed to get a fuller and more detailed
assessment of systematic estimates of the overall levels and patterns of water use, the relative
contributions of different public and private sources of supply as well as the behaviour of the
groundwater table.
* The survey is part of the Centre for Science and Environment’s on-going work on the current
status, problems and prospects of water supply in urban areas of the country.
** Emeritus Professor, Madras Institute of Development Studies, Chennai
*** Former Centre for Science and Environment staff
Scope and Design of Survey
The Survey, conducted during December 2003 and January 2004, was limited to households
within the limits of the Chennai Corporation. Commercial and industrial establishments and
other public and private institutions were not covered. A representative sample of 1510
households was interviewed for collecting data. The 155 wards in the city were grouped into
three broad categories according to the availability and reach of the public system based on
assessment by Metro Water officials. Wards within each of these categories were further
categorized into upper, middle and low-income neighbourhoods. Though this was done in
consultation with several knowledgeable persons, it is necessarily impressionistic. We thus had
nine categories of wards.
A stratified random sampling procedure was used to select a total of 1510 households, the
number that seemed feasible within the constraints of time and resources available. The number
of sample households to be selected in the 9 strata was allocated in proportion to the total
number of households in each of them (obtained from the 1991 census; Since the ward wise
population of 2001 census was not available at the time of study). It was further decided that
households to be surveyed should be selected from a randomly selected sample of the streets
within each sample ward and that at least randomly selected 10 households should be
interviewed from each sample street. The number of sample wards in each stratum and the
number of sample streets in each sample ward was determined on this basis. The sample wards
and sample streets within each of them were chosen through random selection. A total of 1510
sample households in 151 streets located in 31 wards were covered by the survey. Details are
given in the annexure 1. The location of the sample wards is shown in the accompanying map.
The survey schedule (see annexure 2) was designed to elicit information of household
characteristics, the sources on which they normally depended for different uses, and the actual
quantity they obtained from different sources during the day prior to the interview, particulars of
storage tanks and sumps, purchase of water from metro tankers and private tankers, costs of
getting water from different sources, the characteristics of wells/bore-wells (including the time of
their construction, deepening and current and original depth and power source), and
implementation of rainwater harvesting.
The interviews were conducted from late December 2003 through January 2004 by postgraduate
students in social work from the Madras Christian College. Their field work was closely
supervised and the filled in schedules scrutinized by Prof. Annadurai and Dr.Mirium Samuel,
head of that department and Sri J Saravanan. In several cases investigators had to revisit the
households to fill in gaps and get clarifications. An effort was made to get the relevant
information from the head of households as well as female members who are far better informed
about domestic water use. Most were willing to answer all the questions and give information.
However some of the questions and in some cases the instructions to field investigators were not
framed clearly. For instance, the questions relating to quantum of water used from different
sources did not specify the contribution of private tankers. The treatment of multiple occupancy
households and flats raised some difficulties in estimating overall consumption and use because
the schedule did not include questions on the number of households in such cases. Information
relating to water supply and dependence on different sources under ‘usual’ or ‘normal’
conditions and in the current situation is difficult to interpret because of some ambiguities in the
questions.
These problems notwithstanding, thanks to the cooperation of the informants and the effort put in
by the field investigators, the Survey has provided much valuable data to piece together a picture
of the core aspects of sources and use of water, groundwater exploitation and rainwater
harvesting among the sample households, as well as the variations in these features between
different parts of the city and across different income groups. That the estimates of total
consumption by sources and uses based on the survey data are broadly corroborated by estimates
from other independent sources.
Estimates of quantities consumed by purpose and source are based on informants’ recollection of
the number of pots and buckets used the day before the interview. These containers are
generally, but not always, of two or three standard sizes. Moreover, the information obtained is
based not on actual observation but on recollection of the respondents. The data are therefore
necessarily approximate. Nevertheless, a comparison of the estimates of total per capita
consumption from the public system with the Metro Water figures of the quantity supplied
during the survey period suggests that the survey estimates are in the right ball park. Estimates of
per capita consumption for individual uses (except perhaps toilets) also seem plausible.
Characteristics of sample households
The location of the 31 sampled wards can be seen from map 1. Table-1 gives their distribution
according to original stratification by conditions of public supply and a notional assessment of
relative prosperity based on the proportion of households living in slums. The location of the
sample wards is shown in Map 1.
Table 1: Distribution of sample wards by extent of public supply
and average living conditions
UPPER
MIDDLE LOWER
INCOME INCOME INCOME
GOOD SUPPLY
5
5
3
MEDIUM SUPPLY
5
4
2
POOR SUPPLY
3
2
2
The sample households had a total of 6176 members of whom roughly a third (2022) were
children. More than three fourth of the heads of sample households report having secondary or
higher level education. About a third report themselves as self-employed; a little less than half as
having regular employment. About an eighth of them are pensioners. The proportion reporting
casual wage employment is surprisingly small at 6 per cent.
Table – 2: Education and Occupation of the sample house hold head
Total members
Education of house hold head
Adult Children Non literate Elementary Secondary Diploma Degree
6176 2022
110
216
410
86
688
Table – 3: Occupation of the sample house hold head
Occupation of house hold head
Self
Regular EmployeeRegular EmployeeEmployed
Organised Sector
Unorganised Sector
521
442
227
Casual Wage
Employment
129
Pensioner
191
Of the total surveyed house holds about 42% fall in the income group of less than Rs. 5000 per
month, and about 7 percent more than Rs.15000 per month. About 63 percent of the sample
households live in their own houses and the rest in rented accommodation. The sample
households are divided more or less equally between single occupancy homes and multiple
occupancy houses. About 18 percent of the households live in flats. The relative importance of
owned housing and single occupancy also varies with income. As may be expected, the
proportion of households living in own houses and in single occupancy residences increases with
income (Table 4).
Table 4: Characteristics of House holds with different income levels
Household income
No. of
Living in own
Living in single
group in Rs.
households
house
occupancy
<5K
600
309
245
5K – 10 K
397
262
210
10K – 15 K
333
215
277
>15 K
97
83
72
All reporting households 1427
58
118
Total sample households 1510
927
922
Note: some sample households did not provide the information. their number under each
characteristic is indicated as non-reporting
Dependence on sources
The sources of supply as reported by the sample households, and the number of households
reporting different sources are presented in table 5. Roughly 55 percent of the sample households
have direct metro water connections; 64 percent report accessing fixed tanks, taps and hand
pumps provided by Metro Water; and about 11 percent metro tankers. Nearly two thirds of
sample households have their own wells or bore wells. Access through others’ wells and private
tankers is reported by less than 5 percent each of the total households. The fact that the number
of sources is nearly double the number of households shows that Chennaities depend on multiple
sources for their water supply.
Table – 5: Number of households reporting
different means of access to water supply
Sources
Sample households
Public
Direct in-house
834
Outside tap/hp
417
Storage tank
450
Metro tanker
178
Own well
1000
Others well
50
Community well
5
Private tanker
45
Total
2979
This is further highlighted by table 6, which gives the situation at the time of the survey in
respect of sources from which households draw their supplies. Only 40 percent of sample
households report using a single source mostly wells (407 households), followed by metro
tankers (178) and private tankers (45).
Of those who report multiple sources, by far the largest number supplement own well with other
sources; a sizeable number use metro water tankers along with other sources (again mostly wells)
The large majority of households depend on a single source for each purpose, but different
sources for different purposes. A sizeable proportion (ranging from one eighths in the case of
toilets to one fifth for drinking) uses two sources. A much smaller number of respondents use the
three sources. Only 40 percent of sample households report using a single source mostly wells
(407 households), followed by metro tankers (178) and private tankers (45). Of those who report
multiple sources, by far the largest number supplement own well with other sources; a sizeable
number use metro water tankers along with other sources (again mostly wells) (Table 6)
Table 6: Dependence of sample
households on multiple sources
Sources
Own Well and Metro tanker
Own well and Other well
Own well and Community well
Own well and Private tanker
Metro tanker and Other well
Metro tanker and Community well
Metro tanker and Private tanker
Other well and Community well
Own well, Metro tanker & Other well
Own well, Metro & Private tanker
Metro & Private tanker, Other well
Homes
462
23
2
31
116
73
18
1
9
6
1
The pattern of source dependence varies with income. Taking all uses together, (see Table 8) the
proportion of sample households reporting dependence on wells as the sole source increases
progressively from about 11 percent in the lowest to more than half in the highest income group;
dependence on metro tankers is inversely related to income: the proportion being roughly a sixth
of lowest income group and practically zero in the 15+K group; on the other hand, dependence
on private tankers as the sole source is negligible in low income groups and is relatively high (12
percent) in the highest. The incidence of multiple sources does not show a clear pattern.
Table 7: No. of sample households by income group reporting use from various sources
Own well Met
Other
Comm.
Private
Multiple
Total
tanker
well
Well
tanker
sources
Homes
5k
65
106
44
5
2
273
600
5k-10k
101
45
5
0
3
39
397
10k-15k
109
17
1
0
27
159
333
15k-20k
51
0
0
0
12
25
97
105 households in the 5k group, 204 households in the 5k-10k group, 20households in the 10k15k group and 5households in the >15k group haven’t responded
This is further highlighted by table 8, which gives the number of households reporting use of
different sources for different purposes. The following features are noteworthy:
-
Public supply from tap inside and outside the house is used for practically all
purposes more or less with equal frequency.
- Fixed tanks and tankers of the public system are used for drinking and cooking
far more frequently than for other uses
- Wells (own or others’) are used mainly for washing, bathing and toilets.
- Private tanker supply is used by sizeable number of households in all uses, but more so
for purposes other than drinking.
- It is noteworthy that nearly a fourth of the households use bottled water for drinking
and about 8 percent for cooking.
Table 8: Number of sample households using different source for different uses
Uses
Total
Sources
Drinking Cooking Washing Bathing Toilet Other Households
Public in- house
270
271
204
209
187
28
1169
Public outside
49
44
50
50
48
26
267
Public handpump/tap 143
149
150
122
118
29
711
Public fixed tank
176
160
59
62
52
60
569
Public tanker
558
549
228
216
166
28
1745
Own well
153
325
804
808
811
147
3048
Others well
17
31
60
63
60
28
259
Community
well/handpump
5
9
86
85
85
14
284
Private tanker
41
91
97
110
88
37
464
Bottled water
424
114
1
0
0
0
539
Total households
1836
1743
1739
1725
1615
397
9055
The survey data further show that households with less than Rs 5000 per month depend on public
supply both in-house and outside for all the daily uses. Water from public tankers and from fixed
tanks is used mainly for drinking and cooking purposes. Water from private wells is used mainly
for washing and bathing purposes. The dependence of bottled water is very low in this group.
This pattern is noticed in the middle groups as well except that a larger proportion of them
depend on bottled water for drinking. Those in the highest income group depend on public
system to a much smaller extent than others. This group depends more on own wells and private
tankers for all uses except for drinking. The dependence on bottled water is quite high for
drinking and cooking in this group.
Storage devices
Chennai households combine use of multiple sources with the use of overhead tanks and sumps
to store water. Nearly 55 percent of sample households report having overhead tanks (with
capacities ranging from less than 500 litres to over 8000 litres) and somewhat over a fifth have
sumps Capacities ranging between less than 1000 litres to over 10,000 litres). The proportion of
households reporting OHTs and Sumps is relatively higher among single occupancy households.
The incidence of these storage facilities is relatively limited in the case of households in the
lowest income group (where about 28 percent of households report OHT and barely 7 percent
sumps) while it is practically universal in the highest income group (88 percent with OHTs and
75 percent with Sumps)
Table 9: Distribution of OHTs
and Sumps by income groups
Total
No. of homes No. of homes
households with OHT
with Sump
5K
600
171
40
5K-10K 397
289
78
10K-15K 333
300
142
15K-20K 97
86
73
All
1427
846
333
About 83 households of the total sample of 1510 haven’t reported on the monthly income
Patterns of water consumption
Per capita use
Average per capita daily domestic water consumption of sample households during the survey
period (in December 03-January 04) ranged from less than 25 litres to more than 125 litres.
About one third of the households reported consumption rate between 25 and 50 lpcd and around
39 percent between50 and 75 lpcd. The range of variation is considerably reduced if we adjust
for differences in the composition of households in terms of the proportion of adults and
children, Assuming that two children are equivalent to one adult unit,
Table – 10: Frequency distribution of sample house holds by level of per capita daily use
Level of daily use in litres per day
Per capita
of hhs
Per Adult Unit
of hhs
<25
25-50
50-75
75-100
100-125
>125
All
59
475
599
227
113
37
1510
34
366
539
327
172
72
1510
No
No.
Distribution by use
The major part (nearly two thirds) is used for cooking and washing; and a little over a sixth for
toilets. The average use for drinking is 4 lpcd and for cooking 4.9 lpcd. Per capita usage both
overall and for different purposes varies: the coefficient of variation– which is a measure of the
degree of variation – is around 30 percent for total usage; the variation is much higher than
average in the usage for washing and toilet; about the same as average for drinking and the least
for bathing.
Table 11 : Mean Per capita consumption in litres per day for different uses*
Drinking Cooking Washing Bathing
Toilet
Others
Total
Mean
4.0
4.9
22.6
15.1
10.3
1.1
58.1
Standard
Deviation 1.2
1.1
12.2
2.9
4.0
1.8
17.3
0.30
0.23
0.54
0.19
0.39
1.55
0.30
cv
Distribution by source of supply
Metrowater accounts for about 35 percent of the reported consumption of sample households, the
major part of it from tanks, pumps and taps outside the side the house as well as metro tankers.
The major part is from wells – about half the total use is accounted by own wells and the balance
by others’wells.(Table 12)
Table – 12 : Source wise per capita consumption of sample households*
Source
Households reporting
Consumption
number and % of
lpcd % of total
sample household
consumers
Metro Inhouse
321
21
6.8
13
Metro outside
828
55
11.8
22
Own Well
821
54
26.5
50
Other well
351
23
6.3
l1.2
Bottled water
389
25
0.8
1.5
*Excludes private tankers and ‘other sources’
Spatial variations
The levels and patterns of use across sample wards grouped according to the condition of public
supply and the proportion of slum households does not show a clear pattern. This may be due to
the error in the group classification especially by income. The latter, as already mentioned, was
based on the percentage of slum tenements in different wards and some general impressions
about the nature of the neighbourhood.
However, as can be seen from Table 13, the mean per capita consumption is the lowest and the
proportion of total consumption contributed by public systems is the highest in wards rated by
officials as having ‘good’ public water supply. Wards with poor public supply also have a much
lower degree of dependence on public supply but only a slightly higher level of average. It is
interesting that the wards with moderate public supply report the higher level of mean
consumption and also the lowest proportion obtained from public systems.
Table 12 : Consumption levels and contribution of public supply in sample wards
classified by conditions of public supply
Condition of Public
Number of wards
number of wards with number of wards
supply
per capita
where the Public
consumption
system accounts for
<50 lpcd
>50% of total use
Good
13
9
9
Medium
11
3
1
Poor
7
4
2
Variations across income groups
A much clearer pattern emerges when we look at the levels, sources and uses of water by
households classified by incomes as reported in the Survey. (Table 14) Per capita consumption
clearly increases with income. The lowest income group consume around 50 lpcd, and this level
increases progressively to around 80 lpcd in the 15+k group. This is largely a reflection of the
fact that higher income groups consume more for washing, bathing and toilets. The lowest
income group uses nearly a fifth of its total consumption for drinking and cooking, while the top
group uses barely 9 percent. Among other uses, it is washing that seems to be the main reason for
higher level and a larger share of total consumption as incomes increase.
Table 13: Per Capita Consumption based on Reported Use
Group
Drinking Cocking
Washing
Bathing
5K
4.6 (9%) 5.0 (10%) 18.0 (36%) 13.4 (26%)
5K-10K 4.2 (7%) 5.2 (9%) 22.7 (37%) 16.6 (27%)
10K-15K 3.4 (5%) 4.6 (6%) 33.5 (46%) 16.8 (23%)
15K-20K 2.9 (4%) 4.4 (5%) 39.7 (49%) 17.1 (21%)
Toilet
8.1 (16%)
11.6 (19%)
13.4 (18%)
13.2 (16%)
Other
0.8 (2%)
1.3 (2%)
1.2 (2%)
3.4 (4%)
Total
49.9
61.6
72.9
80.7
The poorer households tend to depend more on metro water supply thru tankers and static tanks.
This may be due to the study conducted at a time when the in-house supply was not there. The
table shows that the poorer groups meet more than 50% of their daily requirement from public
supply and the percentage of dependency decreases in higher income groups. The high-income
groups depend more on own well (79%) sources. The dependency on bottled water is also more
in high-income groups.
Table 14: Per capita consumption source wise*
MW.Inside MW.Outside Ownwell
Other’s well Bottled
Total
5K
7.7
17.1
5K-10K 7.9
7.9
10K-15K 2.7
10.8
15K-20K 4.2
1.4
*excludes private tankers.
12.5
33.6
44.2
56.3
9.4
2.5
4.0
6.8
0.4
0.7
1.5
2.3
47.2
52.6
63.2
70.9
Cost of water
To get an idea on the amount spend by each hh to source water, sample house holds were asked
on the annual tax paid to metro-water for water supply, amount spent to purchase water from
tankers and bottled water.
The amount collected as tax per household by metro water is fixed as Rs.50 per month
irrespective of the quantity consumed per household. Users do not pay anything for water from
outside taps and hand pumps provided by Metro water. They are also supposed to get water from
Metro sources outside the house through fixed tanks and mobile tankers free of charge. However
in fact they pay for supply from these sources. The average expenditure is reported to be
Rs.24.70 / Kilo-litre (KL) in the case of static tanks and Rs. 25.70/ KL from metro tankers.
Sample households spend about Rs12.10/KL on the average for water sourced from others wells.
The average cost of bottled water is about Rs.1.30 per litre by purchasing bottled water.
In the case of water sourced from own wells the costs includes payment for energy used for
lifting as wells as depreciation and maintenance, as well as interest on capital costs. We do not
have sufficient information to estimate these costs. However, based on information regarding the
average duration of operation of pumps, the number of wells, and assuming electricity charges at
a notional Re 1 per unit, the energy costs alone would work out to Rs.0.70 per KL.
We did not collect information on the quantum and cost of water taken from private tankers. We
assume that the average cost per tanker of 10,000 litres at Rs. 600. The average household size,
based on the survey, is around 5.2 and the average per capita daily consumption is around 52
litres. The total consumption of an average household works out to 8112 litres per month. Based
on the sourcewise composition of consumption and the rate per KL of different sources, the
average expenditure per house works out to be Rs. 316 per month or Rs. 36 per KL. (Table 15)
Table 15: A rough estimate of cost incurred by an average household for its water
Source
Consumption Total Consumption in litres per
Cost in Rs.
In lpcd
household per month month
Metro Inhouse 6.8
1061
50
Metro outside
11.8
1840
46
Own Well
26.5
4134
4
Other well
6.3
983
12
Bottled water
0.8
125
162
private tankers 4.4
693
42
56.6
8836
316
Estimates of total domestic consumption in Chennai city
The estimates of mean per capita consumption (overall and by major sources) of sample
households in different strata were applied to the estimated total number of households in each of
them. (Table 16) Based on this, the total consumption of the city population from all sources
during the period of the survey works out to 235 million litres per day (mlpd) and consumption
from Metro Water sources to 80 million litres per day.
Table 16: Estimated daily consumption by source,
Chennai Corporation January 2004 (millon litres)
Source
Consumption
% share
Metro in house
Metro outside
house
Own wells/
borewells
Others’ wells
27.8
11.8
52
22.1
123.3
28.3
52.4
12.0
Bottled water
3.9
1.7
Total
235.3
100.00
At the time of the survey, Metro-water accounted for a little over a third of the total
consumption. Surface sources being practically dry during this period, supply through the public
system was entirely from groundwater extracted from wells bore wells and tube wells within the
city limits and from wells outside. Though the survey was carried out at a time when there was
no piped water supply, houses in some wards located in close proximity to the distribution lines
got in-house supply to distribution mains. The greater part of public supply was provided
through fixed public tanks, mobile public tankers and public hand pumps located outside
consumers’ premises.
Sources other than Metro-water – which includes private wells and bore wells, private tankers
and bottled water – accounted for about two thirds of the total domestic water consumption. The
bulk of it was from private wells owned by users. But a sizeable amount (28 million litres) was
taken from wells owned by others or from community wells.
Altogether 98 percent of the total consumption was contributed by groundwater. The balance is
accounted by bottled water.
Estimates of mean per capita consumption (overall and by uses) of the city’s population are
presented in Table 17. Based on this, the total consumption of the city population for all uses
during the period of the survey works out to 255 mld
Table 17: Estimated Daily water consumption for various uses
Uses
Drinking
Cooking
Washing
Bathing
Toilet
Other
Total
Quantity in Million litres
per day
17.7
21.1
100.1
65.7
45.3
5.1
255
It will be noticed that estimated total consumption by source is less than that based on reported
quantities by uses. This difference is partly because the questions relating to source wise
consumption did not elicit information on private tankers. It should also be noted that the
estimate relates only to domestic use. They do not cover consumption by private and public
institutions, commercial and industrial establishments. The total consumption including all users
will obviously be higher than that of households.
The estimates are roughly corroborated by available data on the quantum of metro supply during
the survey period (January 2004), which was marked by acute water scarcity. In this month
Metro Water had introduced a system of supplying some 180 mlpd on alternate days (compared
to some 300-400 mlpd daily in normal years) or an average of 90 mlpd every day which is higher
than the survey based estimate of household consumption of 80 mlpd from metro water. The
difference could be accounted by non-domestic consumption and wastage.
During the survey period the public system depended totally on groundwater extraction ie, water
being tapped from the borewells present in the wells fields of AK basin (which is inclusive of
both government borewells and the water purchased from the farmers whose borewells are in
line with the supply main), southern coastal aquifer, and from the hand pumps fitted within the
city limits. Which means that the total water consumption during scarcity periods includes
public groundwater from outside, inside the city (the private groundwater wells and borewells in
residences) and private water tankers that get water from the wells and borewells located on the
fringes of Chennai city.
The Survey data gives information on the no of sample households with wells in each ward and
in turn for all the nine groups was worked out. From this the total number of private wells in the
city has been estimated as follows: (1) sample households in each of the 9 categories of wards
have been grouped into single occupancy and multiple occupancy households; (2) on this basis,
the total number of single and multiple occupancy households in the city have been estimated;
(3) the number of wells in single occupancy residences is estimated by multiplying the total
number of this class of households and the sample survey estimate of the number of open and
bore wells per household in different strata; (4) in respect of multiple occupancy, we have
assumed that on the average wells in this category serve 4 households. On this basis we estimate
that there are about 4.2 lakh wells ( about 27,000 open wells and nearly 4 lakhs of borewells) in
Chennai city. The average no. of persons per household works out to 5.2 members per house
hold. Considering an average per day extraction of about 400 litres per well per day then the
daily extraction works out to about 168.9 MLD. Also the extraction calculated based on sources
wise consumption (for wells and borewells) works out to about 170 MLD.
Characteristics of wells and their usage
Particulars of Own Well
The particulars of own wells ie., open dug wells and borewells present in the surveyed
households were classified based on the reported income (Table –18). In general the no. of
borewells is more than the open dugwells which is an indication of tapping water from the
deeper source. Of the reported households 8% of them have open wells which are still in use
and 54% depend on borewells. About 7.5% have both open well and borewell. The ratio of no. of
well per house hold was calaculated for all the income group. The poor income group have one
well for every 2 households (with more dependence on the public system) and the rest of the
groups have almost a well in each household.
Table: 18
No. of household
reporting
OW OW in Use
5K
55 42
5K-10K 30 37
10K-15K 39 31
15K-20K 8
5
132 115(8%)
BW
190
279
237
71
777(54%)
OW+BW Total wells
24
311
34
380
37
344
13
97
108(7.5%)
Table : 19 Period of construction
No. of Open Well by Original Date
<1970
5K
15
5K-10K 10
10K-15K 7
15K-20K 2
1970-80
17
27
34
3
1980-90
25
23
23
11
1990-2000
14
4
13
5
No. of Borewell by Original
date
<1970
5
0
2
0
1970-80
1
8
7
3
1980-90
1
59
67
18
19902000
146
229
197
62
In general there is a gradual decline in the construction of open wells after 1980 in all the groups
and the no. of borewell construction increases rapidly after 1980.
Table 20: Characteristics of wells based on Lifting Device,
Type of Pump and Horse Power of Motor
No. by type of
No. by type of lifting device pump
No. by type of HP
Manual Electric
Centrifugal Jet 0.5HP
1HP
5K
45
157
25
170 51
76
5K-10K 17
245
17
274 23
156
10K-15K 13
225
15
251 22
98
15K-20K 2
62
4
80 4
16
77
689
61
775
1.5HP
21
57
75
40
2HP
0
0
5
6
The wells were classified based on the type of lifting device (manual and electric). Manual
extraction is an indication of shallow water table. Only 10% of the wells are used for manual
extraction the rest of them are electric driven.
The wells were also classified based on the type of pump. The working head (water pulling
capacity) of centrifugal pumps is only 30ft below ground level whereas the Jet pumps work up to
200ft. here again more than 90% of the wells are fitted with Jet pumps is an indication of tapping
water from deep water table.
The classification of Motor based on HP also shows similar trend with more wells falling the 1hp
and 1.5 hp motor which is normally used to pump water from depth between 100ft –150ft.
The Sample households were asked about the year of construction of the wells, their original and
current depth. The information for open wells is presented in Table 21, 22 and those relating to
bore wells in Table 23,24. While most could give information on year of construction and
current depth, many either did not know or could not remember the original depth. About 360
sample house holds reported to have open wells of which 65% of them were not in use. More
than three fourths of the wells were constructed before 90. the average depth of the open wells is
about 30 feet below ground level. Most of the borewells were constructed after 1990 with their
average depth around 90feet below ground level.
Table: 21 Year of Construction of Open wells with their mean Current and Original Depth
Year of Construction
Mean Depth
No. of wells
No. reporting
Original
Current
Before 1970
35
10
27.4
28.3
70 – 80
83
48
34.1
33.3
80 – 90
88
47
29.9
27.1
After 90
38
23
31.1
27.7
Total
244
Table : 22 Year of Construction of Open wells with the frequency distribution of depth
Year of
Frequency Dis. Of Open Wells by
construction
depth(ft)
25
50
75
100
Before 1970
7
7
0
0
70 – 80
19
33
4
2
80 – 90
24
24
4
1
After 90
13
9
2
2
Total
63
73
10
5
Table : 23 Year of Construction of Bore wells with their mean Current and Original Depth
Year of Construction
No. of
Mean Depth
Borewells
No. reporting
Original
Current
Before 1970
10
9
55.5
65.5
70 – 80
20
14
87.5
92.1
80 – 90
194
122
90.1
93.5
After 90
664
422
92.7
94.1
Total
888
Table : 24 Year of Construction of Open wells with the frequency distribution of depth
Year of
Frequency Dis. Of Bore Wells by
construction
depth(ft)
50
100
150
200
>250
Before 1970
3
1
0
0
0
70 – 80
2
7
3
2
1
80 – 90
26
83
9
6
11
After 90
70
290
45
44
21
Total
101
381
57
52
33
The house holds were asked to report on the frequency of pump operation in each day and the
duration of hours. It was found that the average rate of pumping of wells to be 1.3 hrs daily
The households were asked to report on the time taken to fill up the over head tank / sump when
the borewell/well is in operation and their storage capacity. Based on this the yield of the
borewells in litres per minute(lpm) was worked out and the results are tabulated in the above
table. About 40% of the wells fall within 16lpm ie., an yield of 1000 litres per hour, 36% of the
households reported an yield of less than 2000 litres per hour and about 24% reported the
borewell yield as more than 2000 litres per hour.
Rainwater harvesting
Due to over dependence on groundwater in the city there has been a progressive decline in the
ground water levels reflected in the decrease of number of open wells in use and increase in the
number of borewells. In order to conserve the groundwater within the city limits there has been a
considerable amount of initiatives taken by the state government in controlling the commercial
exploitation of groundwater. The Chennai groundwater regulation act, which was passed in
1987, was mainly to curb the commercial groundwater exploitation within the city limit. This
was followed by making rainwater harvesting (RWH) mandatory in multistory buildings. During
2001 RWH was made mandatory for all the new buildings and in 2003 it was made compulsory
for all the buildings (existing and new) through an ordinance. But the general opinion about the
implementation of this ordinance is that
 the time frame given was too short
 the structures were not properly designed
 not many trained and skilled labours were available for implementation
 non availability of quality materials for implementation
Hence the households were asked to report on the design, implementation, cost and maintenance.
About 92% of the surveyed households have reported RWH implemented out of which about
86% of the households implemented after the promulgaion of ordinance (ie., after august 2003)
and about 5% before 2002.
With regards to the guidance sought to design the RWH system, nearly 11% got it designed with
the help of Metro water, 12% of the sample households got it designed through consultants.
Fairly large amount of of households (41%) sought the help of local plumbers in designing and
about 24% self designed their own RWH system. 65% - 70% of the households have
implemented rwh designed by plumber or self is an indication of
1. non availability of experts in designing nor the experts help was sort for designing
2. quality of rwh structure (in general households in Chennai opted for the normal bore type
percolation pit which is cheaper but gets clogged and hence in-effective)
Table: Percentage of sample house holds reporting on the help sought from different
agencies for designing RWH system in their houses
Agencies
Approached by % of
house holds to get
RWH design
Metro Water
11%
NGO
0%
Other Consultant
12%
Plumber
41%
Self
24%
Majority (66%) of te sample house holds got the system implemented through plumbers. About
9% engaged authorized contractors, 0.1 % on Voluntary NGO’s and about 11% depended others
to implement.
Table : Percentage of sample house holds reporting on the help sought from different
agencies to implement the RWH system in their houses
Approached by % of
Agencies
house holds to get
RWH design
NGO
0.1%
Authorised Contractor 8.6%
Plumber
66%
Others
11%
With regard to the cost of RWH about 9% have spend less than Rs.1000, 31% have spend
between Rs.1000 to Rs.2000 to get the structures installed. About 16% of the households
reported spending between Rs.2000 – Rs. 3000 and an equal percentage reported spending more
than Rs.3000 to get the structures implemented.
Cost of RWH
Cost in Rs
> 1000
1000 – 2000
2000 – 3000
> 3000
Non reported
Percentage of
Households
9%
31%
16%
15.6%
28.4%
Majority of the households (more than 3/4th) reported tapping roof top water. Just 10% of the
house holds have reported tapping surface run –off.
House holds reporting on the source of harvested water
Source
Roof Water
Surface Water
Both
Non reported
Percentage of
Households
79%
2%
8%
11%
With respect to designs as shown in the table below about 52 % of the sample house holds have
designed a proper system wherein the roof top water diverted to recharge well, percolation pit or
stored in sumps. About 10% of the households have reported faulty structures. The rest have not
reported on the design aspects.
Table: Design characteristics of RWH
RWH Design
Roof top directed to existing OW/BW
Surface water directed to existing OW/BW
Roof top to recharge well
Surface water to recharge well
Roof top to percolation bore pit
Surface water to percolation bore pit
Roof top to percolation pit
Surface water to percolation pit
Rooftop to sump thro filter
Surface water to sump thro filter
Percentage of Sample
Households
38%
4%
9%
0.6%
14%
1.5%
24%
4%
5%
0.8%
Of the total sample house holds 28% were aware of the maintenance required in RWH structures.
Nearly 45% of the households were not aware of the maintenance aspects and 22% have not
responded.