Analysis of Variation of Water Quality in Kelani River, Sri Lanka

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International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-6, Nov-Dec- 2017
http://dx.doi.org/10.22161/ijeab/2.6.1 ISSN: 2456-1878
www.ijeab.com Page | 2770
Analysis of Variation of Water Quality in Kelani
River, Sri Lanka
N.M.DE.A. Abeysinghe1, M.B. Samarakoon2
1Department of Civil Engineering, Faculty of Engineering, General Sir John Kotelawala Defence University, Sri Lanka
2Senior Lecturer, Department of Civil Engineering, Faculty of Engineering, General Sir John Kotelawala Defence University,
Sri Lanka
Abstract This research attempted to analyze the
variation of surface water quality in Kelani River and
finally to create a mathematical model for the Water
Quality Index (WQI) by using the data that have been
obtained. Kelani River is the second largest river in Sri
Lanka while being the most polluted river in the country. It
is one of the main sources of drinking water for human
beings while being the home for many aquatic species. The
ecological aspects of Kelani River are threatened due to
the increasing number of industries along both sides of the
watershed. The present study is conducted to analyze the
water qu ality in Kelani River using s ix p arameters
including pH, Turbidity, Temperature, Total phosphate,
Nitrates, Dissolved Oxygen (DO), and ultimately finding
the Water Quality Index (WQI) by collecting 5 sets of
samples from seven lo cations from March 2017 to August
2017. The highest WQI (72.90) was reported near the
Water Treatment Plant in Biyagama, while the lowest WQI
(62.98) was achieved near the Water Board Pump in
Ambathale. Water quality of five of the sa mples were in
good q uality range and th e other two samples were in
medium quality range. A mathematical model for WQI was
created using the above mentioned six water quality
parameters.
Keywords Kelani River, Surface Water, Water Quality
Index.
I. INTRODUCTION
Water is one of the main sources on which our existence
and settlement are built upon. Water sources can be found
in the forms of rivers, glaciers, rain water, gro und water
etc. Degradation of these natural water resources and
management of available fresh water is becoming more
challenging due to various rea sons such as Climate
change, Geology, topography and soil type. Other than the
natural characteristics of these natural water resources, the
main factor which disturbs the water quality and the
management of these water re sources is the anthropogenic
influence. As a result it has made the water quality and
available fresh water management task more challenging
for the water service providers, especially in developing
countries. Somehow these activities generate contaminants
which finally end up in rivers, streams and oceans through
runoff and disposal of effluents. Climate change and land
use can be identified as the factors that will directly affect
the water bodies available for human and agricultural
purposes. Improper land use will lead to soil erosion
increasing the mobilization of suspended solids in
receiving waters through runoff [1,2,5].
There are 103 natural river basins in Sri Lanka, with a total
length of about 4,500km. However, the i ncreasing demand
of urban activities due to the rapid growth of population
has been affecting the water quality of these river bodies.
It has been identified by several researchers that the
decreasing of water quality in rivers is due to point source
of pollution such as the direct discharges from various land
use types including residential, industrial and agricultural,
and also non-point source of pollutant s such as urban
storm water run-off.
Kelani River is one of the main rivers in Sri Lan ka which
is considered as the most important river as it covers 80%
of the water supply to Colombo. The starting point of the
Kelani River is the Sri Pada mountain range and it travels
along the hill country and finally flows in to the ocean at
Colombo. Apart from being one of the main sources for
potable water, Kelani River is used for transportation,
hydropower generation, fisheries, irrigation, sewage
disposal and sand extraction. T he flow of the river varies
between 800-1500 m³/s during the monsoon and 20-25
m³/s in the dry season, depending on the operation of 3
reservoirs in the catchment. The a nnual sand extraction is
600-800,000 m³ per year. The sand is mined exclusively
by hand. The sand mining causes the river bed to sink by
some 10 cm per year [8].
However the Environmental Foundation Limited (EFL)
has stated that Kelani River is the most polluted and
threatened river in Sri Lanka due to agricultural runoff and
domestic and municipal effluents and the effluents that
have been discharged in to the river by the increasing
number of industries which are located in the close vicinity
of the Kelani River [3].
It has being identified that Kelani River is being pollute d
day by day due the increasing amount of pollutants that are
released into the river. As a result it may reach a point in
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-6, Nov-Dec- 2017
http://dx.doi.org/10.22161/ijeab/2.6.1 ISSN: 2456-1878
www.ijeab.com Page | 2771
the future where it will no longer be obtainable for the
purpose of supplying drinking water. This can be a huge
problem as Kelani River plays a vital role in providing
drinking water to the Colombo city. So understanding the
current status of water quality in Kelani River will be
useful for the future.
The aim of th is study is to find out how the water quality
parameters and the Water Quality Index has been varying
along the Kelani River with the influence of the waste
disposed by different land use types and finally to cr eate a
mathematical model for the Water Quality Index using the
collected water quality data.
II. METHODOLOGY
2.1 Study Area
Samples were collected from seven sampling sites on a
stretch of 8 km alo ng the Ke lani River. Fig. 1 shows the
selected sampling sites namely,
1 Hela Textiles
2 Water board pump division
3 Pattivila
4 Biyagama Water Treatment Plant
5 Kaduwela Expressway Entrance
6 Lion Brew Factory
7 Malwana
Fig.1: Sampling sites
Five sets of surface water samples were collected at
monthly intervals from March, 2017 to August, 2017. P oly
ethylene terephthalate (PET) bottles were used to collect
the water samples and they were tr ansported to laboratory
within 24 hours in a cooler box containing ice.
2.2 Measurement of Parameters
Temperature and Dissolved Oxygen (DO) were measured
using a EUTECH DO meter, pH value was measured by a
HANNA Combined pH/TEMP/MV meter, Total
phosphate and Nitrate was measured using a UV visible
spectrophotometer and Turbidity was measured by a
HACH Turbidity meter . Model and the serial numbers of
these apparatus are given in Table 1.
Table.1: Specifications of apparatus
Apparatus
Model
Serial Number
EUTECH DO Meter
DO600
S/N965992
HANNA Combined
Digital PH/TEMP/MV
Meter
HI2211-02
S/N08702309
UV Visible
Spectrophotometer
DR6000
S/N1569293
HACH Turbidity Meter
2100N
S/N14010C0310
37
2.3 Data Analysis
Microsoft excel 2013 was used to calculate the water
quality index value and to interpret the variations of the
water quality parameters along the Kelani river.
Water quality Index can be found by using the equation
shown in Fig. 2.
Fig.2: WQI equation
Here, the corresponding q values for the raw data must be
taken from the standard q value graphs. Each of the water
quality factors is assigned a weighting factor which
signifies its importance [6].
A mathematical model for the Water Quality Index was
created using The R Project for Statistical Co mputing with
the use of collected water quality data.
III. RESULTS AND DISCUSSION
The final results obtained for each and every seven
sampling sites are given in Table 2.
3.1 Dissolved Oxygen
The dissolved oxygen (DO) is the amount of oxygen that is
dissolved in water. The Dissolved Oxygen (% sat) values
for this study varied between 19.63 and 41.45. T he oxygen
dissolved in lakes, rivers, and oceans is very important
when it comes to the living of the organisms and creatures
in it. The quality of water can be affected, as the amount of
dissolved oxygen drops below normal levels in water
bodies. As a result the organisms and creatures livi ng in it
may die. Moving water contains a large amount of
dissolved oxygen while stagn ant water has less amount of
dissolved oxygen. If the DO concentration is high, then the
quality of water can be considered as good [7]. The
maximum DO value (41.45) was recorded near the
Biyagama Water Treatment Plant while the minimum DO
value (19.63) was recorded near the Hela Textiles
Company. The standard value for DO (% sat) is given as
40 or more and here, only one sample has passed that
International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-2, Issue-6, Nov-Dec- 2017
http://dx.doi.org/10.22161/ijeab/2.6.1 ISSN: 2456-1878
www.ijeab.com Page | 2772
value. The variation of DO along the selected area of the
Kelani River is given in Fig. 3.
Fig.3: Variation of DO (%sat)
Fig.4: Variation of pH (units)
3.2 pH value
pH is an important parameter for water quality
measurement. It is a measure of the acidity or alkalinity of
the water. It can also be identified as the measure of
hydrogen ion concentration. The pH scale ranges from 0 to
14. The highest pH value was recorded near the Kaduwela
Expressway Entrance while the lowest pH value was
recorded near the Hela Textiles Company.
Table.2: The average value of each parameter
Parameter
1
2
3
4
6
7
DO (% sat)
19.63
19.91
34.47
41.45
36.61
27.47
29.77
pH
5.95
6.07
6.34
6.52
6.68
6.62
6.52
Turbidity (NTU)
8.13
4.54
9.27
9.41
6.16
11.84
9.31
Temperature (0C)
28.32
28.28
28.44
28.36
26.14
27.96
26.66
Total Phosphate (mg/L)
0.09
0.36
0.08
0.17
0.46
0.14
0.09
Nitrate (mg/L)
0.70
1.28
0.58
0.60
0.46
0.34
0.56
WQI
65.24
62.98
70.40
72.90
70.22
70.03
70.37
The normal range of pH for surface water is 6.5 to 8.5 [7].
Here, four of the samples are in the normal range. The
variation of pH values is given in Fig. 4.
Fig.5: Variation of Turbidity (NTU)
3.3 Turbidity
Turbidity is the amount of cl oudiness in the water. Water
with high turbidity is cloudy, while water with low
turbidity is clear. When the turbidity is high, water will be
less aesthetically pleasing and also sunlight will warm it
more. As a result temperature o f the water will be
increased. Turbidity is measured by Nephelometric
Turbidity Units (NTU). T he turbidity of surface water is
usually between 1 and 50 [7]. The maximum turbidity
value (11.84 NTU) was recorded near the Lion Brew
Factory and the minimum turbidity value (4.54 NTU) was
recorded near the Water Board Pump Division. The
variation of turbidity of the samples is shown in Fig. 5.
3.4 Temperature
Temperature is a critical water quality and environmental
parameter. It impacts the dissolved oxygen levels,
chemical processes, biological process, water density and
stratification of a river. The temperature of surface water is
usually between 0ºC and 30ºC and all the values which
were obtained are in this range [7]. The highest
temperature (28.44 0C) was recorded near Pattivila area
while the lowest temperature (26.14 0C) was recorded near