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Assessment of the Effect of Aruwakkalu Waste Dump 
on Surrounding Water Resources
Chirantha D, Herath HMDK, Chandrapala HMNI, *Chaminda SP, 
Dassanayake ABN and Jayawardena CL 
 
Department of Earth Resources Engineering, University of Moratuwa, Sri Lanka 
 
*Corresponding author – chaminda@uom.lk 
Abstract 
In developing countries like Sri Lanka, waste management is a vital necessity. Solid waste 
dumps play a major role in handling waste in most countries. These solid waste dumps can 
cause severe environmental pollution via leachate generation and transport of toxic material 
along with both surface and underground water flows. The Aruwakkalu waste dump, which 
is the subject of the study, is a sanitary landfill situated in Puttalam district, Sri Lanka. The 
landfill is planned to receive and store municipal solid waste (MSW) from Colombo 
metropolitan area. Locations for these waste dumps must be selected strategically to 
minimise the risk of contamination of the surrounding environment. A distributed 
hydrological model was used to determine the effect of rainfall, evapotranspiration, and 
surface runoff on the site. It identified the direction of the water flow through the waste 
dump. The analyses have illustrated that the area receives lesser rainfall and a higher rate of 
evapotranspiration. The hydrological analysis illustrates the water flow direction from the 
waste dump to the outside is towards the West and away from the nearby settlement areas. 
The results were used to assess the effect of the waste dumpsite on the surrounding water 
resources. 
Keywords: Evapotranspiration, Flow direction, Hydrology, Landfill, Rainfall 
 
1. Introduction 
Solid waste is one of the leading 
undisputable problems in most developing 
countries. With increasing population and 
urbanisation, the management of solid 
waste is getting complicated day by 
day [1]. 
Solid waste is considered as any non-
flowing/non-fluidic substance which has 
no use or no immediate economic demand. 
Municipal solid waste (MSW) can be 
generated via various human aspects such 
as domestic, hospital, industrial and 
agricultural activities [1]. The quality and 
the quantity of the MSW depends on many 
factors such as population, lifestyle, food 
habits, standards of living, the extent of 
industrial and commercial activities, 
cultural practices, and climate. The 
collection, transportation, and disposal of 
MSW in unscientific ways caused chaotic 
results in many countries [2]. 
One of the main means of waste disposal is 
by sanitary landfills, where waste materials 
are spread over the land surface and 
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covered and compressed by soil. These 
landfilling sites can cause surface water as 
well as groundwater pollution unless 
proper management and monitoring are 
done [3]. 
Solid waste in these landfills causes 
environmental pollution as well as water 
pollution both on the surface and 
underground. Direct precipitation on the 
site and surface runoff through the site can 
carry the waste unless the dumpsites are 
properly designed [4]. Precipitated water 
can be easily mixed with waste materials in 
the dumpsite and produce a mixture called 
leachate. This mixture can access nearby 
surface water flows and groundwater 
aquifers unless proper controlling 
measures are implemented [5].  
In Sri Lanka, the Aruwakkalu sanitary 
landfill located in Puttalam district is one 
of the recently designed MSW dumpsites, 
which is at the final stages of completion. 
The people living in the vicinity of the 
dumpsite consume well water as their 
primary water source. The location of the 
dumpsite and the effect of surface water 
runoffs are critical factors which determine 
the degree of impact on waste dump 
contaminants on these settlement areas. 
Runoff modelling and hydrological 
analyses are commonly used to determine 
the effect of precipitation, 
evapotranspiration, and water flow 
direction in an area. These methods can 
illustrate the nature of the water flow and 
the potential changes of the hydrology of a 
site utilising key factors like precipitation, 
temperature, elevation, and surface water 
flow. 
This research study is mainly intended to 
determine the nature of the surface flow 
along the waste dump area and to 
determine the possibility of water 
contamination of the nearby settlements 
via surface runoff. 
 
 
Figure 1: Study area location map. 
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2. Methodology 
2.1 Study Area 
The Aruwakkalu sanitary landfill is 
situated in Puttalam District, Northwestern 
province of Sri Lanka. Upon completion, it 
is expected to receive 1600 metric tons of 
waste daily. The waste dump is planned to 
store more than 4.7 million m3 solid waste 
in the coming ten years [6]. 
As illustrated in Figure 1, the waste dump 
location is in the proximity of the Puttalam 
lagoon, and there are several settlement 
areas like Sewarakkuli, Karaitive, 
Periyanaga Villu etc. The area receives a 
total average annual rainfall of 2500 mm, 
and the temperature ranges from 23° C to 
34.4° C [6]. 
 
2.2 Project Flow 
 
The flow of the project can be logged into 
four parts. 
1. Data acquisition 
2. Model setup 
3. Hydrological analysis 
4. Analysis of results 
 
2.3 Data Acquisition 
 
 
Figure 2:  Locations of the Kala Oya Basin 
in Sri Lanka. 
 
Figure 3:  Locations of meteorological 
stations relative to the Kala Oya basin. 
Data for the surface runoff model was 
collected as per the requirements from the 
Department of meteorology, Sri Lanka. As 
illustrated in Figure 3, daily rainfall data 
and maximum and minimum temperature 
data of 5 stations for the selected Kala Oya 
basin were acquired. The location of the 
Kala Oya basin in Sri Lanka is illustrated in 
Figure 2, and the selection of the Kala Oya 
basin was made considering the location of 
the Aruwakkalu waste dump. 
Digital Elevation Model (DEM) files with 
12.5 m resolution and 30 m resolution were 
acquired from the USGS and ASF archives.  
2.4 Model Setup 
 
The model setup consists of the 
preparation of the surface runoff model 
using rainfall and evapotranspiration 
maps, and the model inputs are given in 
Table 1. 
The model is designed to determine the 
variations of precipitation and 
evapotranspiration of the Kala Oya basin. 
The model is employed with a self-written 
Fortran program which consumes daily 
rainfall, daily maximum, and daily 
minimum temperature data as main inputs. 
Using the Hargreaves equation, the 
potential evapotranspiration is determined. 
12.5 m resolution digital elevation file was 
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obtained from ALOS PULSAR satellite. The 
DEM file was resampled into 100 m 
resolution.  
Table 1: Input data for the model 
Required Data Source(s) 
Daily rainfall 
(2008-2010) 
Department of 
meteorology 
Daily maximum 
and minimum 
temperature data 
(2008-2010) 
Department of 
meteorology 
Elevation data 
(DEM) 
USGS SRTM digital 
elevation model 
Catchment 
boundary and 
terrain 
SRTM and ALOS 
PULSAR digital 
elevation models 
Soil data 
World soil map 
and literature 
Land use map 
Sentinel 2 satellite 
image classification 
via Arc Map 10.5 
Data from 5 meteorological stations from 
2008 to 2010 were used to map the rainfall 
and evapotranspiration of the basin via the 
inverse distancing method. The location of 
each station with relative to the basin was 
given using a latitude grid of the same size 
(1063 columns and 701 rows). 
All these above parameters and procedures 
were included in the self-written Fortran 
code. The outputs of precipitation and 
evapotranspiration were in binary format. 
They were visualised using Envi Classic 5.0 
and ArcMap 10.5, and the variations were 
studied. 
The location of the Aruwakkalu waste 
dump site is in the vicinity of the selected 
basin. Using the variations and trends 
observed within the basin, the impact of 
precipitation and evapotranspiration on the 
surface water flow along the waste dump 
was determined. 
2.5 Hydrological Analysis 
 
The hydrological analysis was carried out 
using the digital elevation models (DEM) 
via Arc Map hydrological Analysis tool. 
The DEM files were used to create flow 
accumulation of the area. Flow direction 
file was created using the flow 
accumulation to determine the direction of 
the water flow through the area.  
A buffer zone of 1 km around the 
Aruwakkalu waste dump was extracted 
from the original flow direction file. A 
threshold value of 2000 was used to 
enhance the water flow paths of the area.  
Together with the results of the 
hydrological analysis and the digitised 
location map of the surrounding 
settlements, the degree of water 
contamination of the nearby villages was 
determined. 
The location of the dumpsite within the 
basins and the elevation of the dumpsite 
location relative to the surrounding areas 
were further analysed to determine the 
water flow direction and the effect of water 
flow on the location. 
3. Results 
3.1 Results of the Model 
The model was created by the self-written 
Fortran code, and the resulted precipitation 
and evapotranspiration files were in binary 
format. They can be visualised via Envi 
classic 5.0 and Arc Map 10.5 software. 
Monthly variations of years from 2008 to 
2010 were taken as outputs for analysis of 
the effect of surface running water along 
with the waste dump site. 
 
Figure 4:  Rainfall map for January         
2008. 
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The circled area of Figures 4 and 5 is the 
area extent where the waste dump is 
located within the basin. 
Figure 4 and Figure 5 are the resultant 
rainfall and evapotranspiration maps 
generated from the Fortran code for the 
month of January 2008. A total of 72 files 
for precipitation and evapotranspiration 
were output by the model, and they can be 
visualised as GIF files to illustrate the 
variations. 
 
Figure 5:  Evapotranspiration map for 
January 2008. 
 
Figure 6: Average monthly rainfall 
variations, evapotranspiration, surface 
runoff and infiltration. 
The average monthly precipitation, 
evapotranspiration, surface runoff and 
infiltration are graphically illustrated in 
Figure 6. 
3.2 Results of Hydrological Analysis 
The result of the hydrological analysis is 
illustrated in Figure 7. 
 
Figure 7: Hydrological map of the 
Aruwakkalu waste dump area. 
4. Discussion 
The modelling process was carried out to 
the Kala Oya basin, and it was observed 
that the location of the Aruwakkalu waste 
dump is in the boundary regions of the 
Kala Oya basin and the basin which is 
situated in the south of the Kala Oya basin. 
 
Figure 8: Position of the waste dump and 
1 km buffer zone on two basins. 
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In the hydrological analysis illustrated in 
Figure 7, water paths through the waste 
dump area and the buffer zone were 
determined using a very low threshold 
value of 2000. This value was selected as 
there was no major or significant water 
flow through the area under higher 
threshold values which are commonly used 
to generate major water networks in basins. 
The elevation of the waste dump area was 
also considered in the study to further 
determine the water flow direction and to 
analyse the position of the waste dump 
relative to the surrounding areas. 
The precipitation and evapotranspiration 
models, which are created as stacks starting 
from Figure 4 and Figure 5 clearly indicate 
that the area that belongs to the 
Aruwakkalu waste dump (circled area) 
receives lesser precipitation and is 
subjected to higher evapotranspiration 
than the average values of the basin. 
Figure 6 also illustrates that more than 55% 
of the average annual rainfall is removed 
from the area as evapotranspiration. This 
affects the surface runoff of the area as the 
generation of runoff is lesser with low-
intensity rainfall and high-intensity 
evapotranspiration. 
As illustrated in Figure 8, the location of 
the Aruwakkalu waste dump is in the 
boundary areas of the two basins. Also, the 
location is in low elevation than the 
surrounding areas. The amount of running 
water through the area is minimum due to 
the location at basin boundaries, and as 
illustrated in Figure 7, the flow of the 
surface water is towards the lagoon and 
away from the nearby settlements. 
The hydrology analysis clearly illustrates 
that the water flow gradient extends away 
from the surrounding settlements within 
the 1 km buffer zone. The effect of 
contamination of water sources through 
surface running water is minimum. 
The EIA report [6] reveals that according to 
the boring tests carried out, the 
groundwater level fluctuates between –0.05 
and -6.85 meters. Thus, the bottom 
foundation level of the sanitary landfill is 
higher than that of the groundwater. But in 
case of a rise in the groundwater table 
during the rainy season, a bottom liner 
system is placed to drain the groundwater 
from the site [6]. 
The development of the floor of the waste 
dump is carried out with layers of in situ 
soil and bentonite. Further, the HDPE sheet 
layer is used to reinforce the floor by 
reducing the permeability [6]. 
According to the EIA report, there is no 
history of major floods in the area. There 
were several minor flooding that occurred 
up to 3 MSL contour levels. Since the waste 
dump is located above 5 MSL, there will be 
a lesser impact from flooding in the 
future [6]. 
Accumulated drainage flows along minor 
undulations, and valleys in the area have 
formed rills causing erosion and fines 
washout in the sloping ground areas. These 
flows are finally diverted to the abandoned 
quarry pits in the North-west and 
Northside boundaries of the waste dump, 
and stagnant water is presumed to remain 
for a short duration after rainfall events 
before vanishing due to seepage losses and 
direct and soil evaporation. The average 
annual reference evapotranspiration and 
potential soil evaporation are relatively 
high in this arid region [6]. 
According to the borehole tests carried out, 
the groundwater levels were not 
encountered at any borehole pit, even 
though the bored pits were driven up to a 
maximum depth of 33.45 m and 58.00 m, 
respectively [6]. 
5. Conclusions 
From the results of the model obtained 
from the hydrological model, it can be 
cognitively concluded that more than 55% 
of precipitation in the Kala Oya basin goes 
out as evaporation and transpiration. The 
rest is turned to surface runoff and 
infiltration.  
Further, it can be concluded that the lagoon 
area is more vulnerable than the water 
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sources in the settlement areas in case of a 
possible contaminant leakage from the 
waste dumpsite. 
The findings of the EIA report of the 
Aruwakkalu waste dump conclude that the 
effect of pollution from the waste dump to 
the surrounding surface water as well as 
groundwater environment is less. 
Following this study, further investigation 
of the groundwater profile of the area 
should be conducted to determine the 
groundwater flow trends of the area. 
Further, a detailed groundwater quality 
assessment should be conducted in both 
upstream and downstream areas of the 
waste dump, covering both the wet season 
and dry season of the year. 
Acknowledgements  
We would like to extend our heartfelt 
gratitude to the following personnel who 
helped us in many ways to conduct this 
research project. Firstly, we would like to 
acknowledge the staff members of the 
Department of Meteorology for providing 
necessary data sets upon request. Finally, 
we would like to acknowledge the 
academic staff and the non-academic staff 
of the Department of Earth Resources 
Engineering, University of Moratuwa, for 
their immense support and contribution 
towards the project success. 
 
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