Influence of anthropogenic activities and seasonal variation on groundwater quality of Kathmandu Valley using multivariate statistical analysis
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Water Quality: Current Trends and Expected Climate Change Impacts (Proceedings of symposium H04 67
held during IUGG2011 in Melbourne, Australia, July 2011) (IAHS Publ. 348, 2011).
Influence of anthropogenic activities and seasonal variation on
groundwater quality of Kathmandu Valley using multivariate
statistical analysis
DHUNDI RAJ PATHAK1,2, AKIRA HIRATSUKA3 & YOSUKE YAMASHIKI4
1 Solid Waste Management & Resource Mobilization Centre, Ministry of Local Development, Government of Nepal,
Kathmandu, Nepal
drpathak@ymail.com
2 Engineering & Geotechnical (E. & G.) Consult (P) Ltd, Kathmandu, Nepal
3 Department of Civil Engineering, Osaka Sangyo University, 3-1-1 Nakagaito, Daito, Osaka 5748530, Japan
4 Disaster Prevention Research Institute, Kyoto University, Kyoto 606-8501, Japan
Abstract Increasing anthropogenic activities in Kathmandu, the main urban centre of Nepal, have mounted
heavy stresses on groundwater quantity and quality. Changing climate reflected by significant annual
variations in temperature and precipitation may further exacerbate the situation, which will have a direct
impact on groundwater levels, reserves and quality. In this study, several water quality parameters were used
as possible indicators to trace the impact of anthropogenic activities on the groundwater quality of
Kathmandu using multivariate statistical analysis. Impact of climatic and seasonal variations on groundwater
quality was also discussed. Compared to the dry season, groundwater sources sampled during the wet season
were more contaminated. The reasons for higher contamination levels during the wet season were probably
due to the high recharge resulting in a shallow water table, and supplemented by leakages from septic tanks,
haphazard disposal of solid waste and sewage.
Key words multivariate statistical analysis; groundwater quality; anthropogenic activities; climate change;
seasonal variation; Kathmandu, Nepal
INTRODUCTION
In Kathmandu, the main urban centre of Nepal, people largely depend upon groundwater to meet
day-to-day water needs because of the inadequate and unreliable piped water supply. Rapid
urbanization and the increasing population demand more agricultural, industrial and domestic
supplies. People use a variety of groundwater sources comprising of dug wells, tube wells, stone
spouts and deep tube wells (Khadka, 1993). Most people use either tube wells or dug wells to tap
shallow groundwater for logistic and economic reasons. In addition, stone spouts are one of the
traditional and trusted alternatives to municipal piped water supply in Kathmandu. These spouts
are excavated brick-lined structures that tap the shallow groundwater, which can also be a part of a
series of spouts. They are distributed throughout the valley, both in dense urban and village
settings. Generally, shallow groundwater is susceptible to fluctuation of water quality within
relatively short time scales and therefore can be used as an indicator of anthropogenic activities at
and/or near the ground surface such as disposal of solid waste, leaching of septic materials and
infiltration of sewage and wastewater from poorly managed sewerage systems. Similarly, all the
rivers in the valley have been polluted due to improper disposal of solid waste on the riverbanks,
and direct discharge of untreated sewage and wastewater into the rivers. The highly permeable
alluvial river deposits facilitate mass transportation phenomena resulting in further deterioration in
groundwater quality. Thus, the interaction between groundwater and the surface plays a distinctive
and significant role in the present hydrogeological situation. Changing climate, represented by
annual variations in temperature and precipitation, may have adverse impact on changes in
groundwater quantity and quality.
Several researchers have studied the groundwater quality of Kathmandu (Khadka, 1993;
Chettri & Smith, 1995; Jha et al., 1997; ENPHO, 1999; Khatiwada et al., 2002; GWRDB, 2000,
2001; JICA & ENPHO, 2005; Warner et al., 2008; Pathak et al., 2009, Panta, 2010). As discussed
in several previous studies, anthropogenic activities influence the shallow groundwater regime
warranting regular monitoring. However, systematic investigations on the current status and trends
of groundwater quality and its relation to various anthropogenic activities, climate change and
Copyright © 2011 IAHS Press68 Dhundi Raj Pathak et al.
seasonal variations have not been carried out in the region. Therefore, it has become imperative to
elucidate and investigate the factors effecting groundwater quality and quantity. This will facilitate
the design and development strategies that can protect the environment and prevent further
deterioration of the affected systems. In this study, various water quality parameters were used as
possible indicators to trace the impact of anthropogenic activities on the groundwater quality of
Kathmandu using multivariate statistical analysis. In addition, impacts of climatic and seasonal
variations on groundwater quality are discussed.
METHODS
Description of study area
Water quality data were sampled from the groundwater aquifers, including samples from dug
wells, shallow tube wells and deep tube wells, in Kathmandu Valley, the main urban centre of
Nepal (Fig. 1). Kathmandu Valley includes five of the 58 municipalities of the country, including
three major cities; Kathmandu, Lalitpur and Bhaktapur.
Fig. 1 Study area.
The current population of Kathmandu Valley is estimated to be about 3 million people, which
is about 30% of the total urban population. Kathmandu-centric development has resulted in rapid
urbanization in the valley. The rapid urbanization in Kathmandu is stretching municipal boundaries,
converting open spaces and agricultural fields into concrete jungles. Between 1984 and 2000,
agricultural land in the valley has decreased from 62% to 42%. If this trend continues, by 2025
there will be no agricultural fields left in this once fertile valley (ICIMOD, 2007). The unplanned
and haphazard urbanization in the valley have led to poor drainage and sanitation. The solid wastes
are disposed along the riverbanks and the untreated sewage and wastewaters from domestic and
industrial areas are directly discharged into the rivers (Fig. 2) rendering them as open sewers.
The Kathmandu Valley can be considered to be a closed groundwater basin with several
independent or interconnected aquifers. In general, the aquifers in the Kathmandu Valley can be
divided into shallow and deep systems that provide residents with drinking water. The upper
unconfined aquifers are composed of unconsolidated coarse sediments, but become confined at a
greater depth due to the presence of extensive clay layers. The shallow unconfined aquifers occurAnthropogenic activities and seasonal variation on groundwater quality in Kathmandu Valley 69
at depths below 10 m, while the deep confined aquifers occur at around 310–370 m (Khadka,
1993). In addition, isolated confined aquifers are located at significantly deeper levels (Gautam &
Rao, 1991). The objective of this study is to investigate the influence of anthropogenic activities
and seasonal variation on groundwater quality in the unconfined shallow aquifers, which are
exploited by many dug wells, tube wells and traditional stone spouts. The shallow aquifers are
recharged mostly along the basin margins, directly from precipitation and by supply from several
small rivers. Average annual precipitation in the Kathmandu Valley is around 1400 mm of which
80% occurs during the monsoon from June to September. The shallow aquifers of the valley are
characterized by a high recharge rate.
Discharge of untreated
wastewater Improper dumping of solid waste on
the bank of rivers
Fig. 2 Solid waste disposal on the river banks and the direct discharge of untreated sewage and
wastewater into the rivers.
Groundwater quality parameters
The data sets on quality parameters of water samples collected from shallow groundwater systems
of Kathmandu, including stone spouts, dug wells and shallow tube wells, in different time
windows from 1999 to 2008 were analysed to trace the impact of anthropogenic activities, climatic
and seasonal variations on groundwater quality. The data sets of 120 water quality sampling sites
comprising 16 quality parameters obtained from ENPHO (ENPHO, 1999) and 253 water quality
sampling sites comprising 8 water quality parameters obtained from ENPHO & JICA (ENPHO &
JICA, 2005), were used to study the influence of anthropogenic activities. In addition, nitrate-N
values from shallow groundwater aquifers sampled by the authors in September and October of
2008 were also utilized in this study. Further selected water quality characteristics of shallow
groundwater sources, including dug wells and shallow tube wells sampled during the wet
(monsoon) and dry (winter) seasons by the Ground Water Resources Development Board
(GWRDB) of Nepal (GWRDB, 2000, 2001), were used to trace the impact of climatic and
seasonal variations on the groundwater quality of Kathmandu Valley.
Multivariate statistical analysis
Groundwater water quality parameters were subjected to basic descriptive statistical parameters
and multivariate analyses, such as principal component analysis (PCA) and factor analysis (FA),
for interpretation of groundwater quality. Spearman’s rank correlation coefficient was used to
calculate the correlation between the variables. All mathematical and statistical computations were
made using Microsoft Office Excel 2003 and SPSS 17. PCA expresses the association between
variables with reducing dimensionality of data structure. It involves the transformation of the
original variables into new uncorrelated ones called principle components (PCs), which is
accomplished on the diagonals of the correlation matrix (Vega et al., 1998; Helena et al., 2000).
The principal component (PC) can be expressed as:
z ij = a i1 x1 j + a i 2 x 2 j + a i 3 x3 j + ..... + a im x mj (1)70 Dhundi Raj Pathak et al.
where z = the component score, a = the component loading, x = the measured value of variable,
i = the component number, j = the sample number and m = total number of variables. FA followed
by PCA reduces the contribution of less significant variables to simplify even more of the data
structure coming from PCA. This purpose can be achieved by rotating the axis defined by PCA
according to well-established rules and constructing new groups of variables, which are also called
varifactors (Vega et al., 1998; Helena et al., 2000; Chapagain et al., 2009). The FA can be
expressed as:
z ji = a f 1 f1i + a f 2 f 2i + a f 3 f 3i + ..... + a fm f mi + e fi (2)
where z = the measured variable, a = the factor loading, f = the factor score, e = residual term
accounting for errors or other source of variation, i = sample number and m = the total number of
factors.
RESULTS AND DISCUSSION
Results of multivariate statistical analysis
PCA was used as an extraction technique to investigate the chemical characteristics of ground-
water and to distinguish the anthropogenic processes affecting groundwater quality in the system
after which the factor loadings matrix was rotated to an orthogonal simple structure according to
the varimax rotation technique. From the 1999 and 2005 groundwater quality data sets, PCs were
extracted on the symmetrical correlation matrix computed with the 16 and 8 variables, respectively.
The first five components and three components extracted have eigen values greater than 1,
and account for 78% and 60% of the total variance in the 1999 and 2005 data, respectively. To
maximize the variance of the extracted principal axes, the varimax normalized rotation was
applied (Cloutier et al., 2008). In the 1999 data set, PC1 represents the hardness loading, which
explains the greatest amount of variance (22%). This component is characterized by highly
positive loadings in total hardness (0.97), calcium (0.89), magnesium (0.86) and conductivity
(0.72). The high loading factor of conductivity is likely due to the contribution of high
concentrations of dissolved ions in the groundwater. PC2, which accounts for 17% of the total
variance, contains high loadings of temperature (0.67), turbidity (0.58), phosphate (0.82) and
ammonia (0.8). The variables nitrate-N (0.83), chloride (0.82) and total coliform (0.75) contribute
most strongly to the third component (PC3), which explains 17% of the total variance associated
with anthropogenic activities influencing the shallow aquifers, such as septic tank leachate,
domestic sewage, industrial effluent, and solid waste disposal. The significant correlation of
nitrate-N with chloride, nitrate-N with total coliform and chloride with total coliform also support
this interpretation. PC4 explains 14% of the variance, which is mainly related to ferrous iron (0.7),
manganese (0.69), turbidity (0.63) and E. coli bacteria (0.69), assumed to be indicative of
industrial pollution. PC5 projects 7.6% variance relating to high loadings of pH.
Similarly, in the data set of 2005, PC1, which accounts for 23% of total variance, contains
high loading for ferrous iron (0.84), manganese (0.74) and ammonia (0.66), which is attributed to
the influence of domestic and industrial wastes. PC2 explains 21% of variance and is associated
with high negative loading of pH (–0.83) and positive loading of depth (0.60) and conductivity
(0.71). PC3 accounts for 15% of total variance and is associated with high loadings for nitrate and
age of the groundwater sources. This indicates that long-term urban anthropogenic activities, e.g.
poorly designed septic systems and inadequate containment and treatment of sewage, may be
directly related to nitrate contamination in the traditional water sources, such as stone spouts and
some dug wells installed at old urban centres that have been used as “safe” drinking water sources
for hundreds of years in Kathmandu.
Seasonal and climatic water quality variations
Of contaminants originated at or near ground surface due to different anthropogenic processes,
nitrate, BOD, total coliform, faecal coliform, sulphate, phosphate, ammonia and manganeseAnthropogenic activities and seasonal variation on groundwater quality in Kathmandu Valley 71
Concentration (mg/L, CFU/100); 10 x
coliform bacteria & 10 x sulphate 8
Monsoon Winter
7
6
5
4
3
2
1
0
Manganese
Nitrate
Ammonia
Sulphate
Phosphate
BOD
Coliform
Coliform
Fecal
Total
Water quality parameters
Fig. 3 Concentration of selected contaminants in the monsoon (wet season) and winter (dry season).
concentrations tend to be highest during the monsoon (wet season) period corresponding to high
rainfall intensity and groundwater recharge, compared to the drier winter season (Fig. 3).
Considering that precipitation and corresponding recharge are typically highest from June to
September, it follows that contaminant concentrations tend to be higher during these months.
Climate change would further increase this seasonal imbalance due to the occurrence of higher
rainfall during the rainy season and less rainfall during the dry season. An analysis of 30 years of
rainfall data at Kathmandu indicates that rainfall (1125.6 mm) during the monsoon (June–
September) is about 80% of total average annual precipitation. Climate change also could affect
groundwater quality by changing the vulnerability of shallow aquifers to diffuse pollution. The
case study presented for shallow aquifers in Kathmandu employs vulnerability indices for the
susceptibility of aquifer to pollution (Pathak & Hiratsuka, 2010). The indices were derived from
GIS-based methods such as DRASTIC (Depth to water, net Recharge, Aquifer media, Soil media,
Topography, Impact of the vadose zone and hydraulic Conductivity) and a fuzzy pattern
recognition model based on the DRASTIC system. The analysis suggests that depth to the water
table and recharge are the most important parameters in determining aquifer vulnerability. During
the wet season, the rising water tables due to the higher amount of recharge through porous sandy
soils is accompanied by an increase in the transport of contaminants, i.e. from leaching of septic
tanks, the poorly managed sewerage system and solid waste disposal. In addition, improper solid
waste disposal and leachates from septic systems cause the germination of harmful vectors, viruses
and bacteria, especially during the monsoon (wet season). Climate change is expected to change
the frequency and magnitude of extreme weather events, which will further contribute to changing
patterns of morbidity and mortality associated with vector-borne and water-borne diseases
(Marashini, 2010).
Current status of nitrate in groundwater: possible indicator of anthropogenic activities
The quality of water extracted from groundwater sources of Kathmandu Valley, especially from
the shallow aquifers is under threat of degradation by nitrate, coliform bacteria and other
contaminants because of different anthropogenic activities, resulting from rapid, unplanned and
haphazard urbanization of the entire valley. Nitrate-N is commonly used as an environmental
indicator to trace the impact of anthropogenic activities on groundwater. Nitrate-N ranged from 0.0 to
26 mg L-1 in shallow groundwater systems of Kathmandu, where 16% of the sampled wells
exceeded US Environmental Protection Agency (USEPA) guidelines of 10 mg L-1 as nitrate-N
(USEPA, 2009). However, another 33% of the wells have high nitrate-N concentrations ranging
from 2 to 10 mg L-1 (Pathak et al., 2009). Extremely high nitrate-N concentrations (>10 mg L-1)
have been observed, particularly in the northern areas of the valley. This area is dominated by72 Dhundi Raj Pathak et al.
sandy formations and contains an old city where many households use septic tanks. Therefore,
nitrate contamination for the shallow aquifers in Kathmandu Valley is mostly due to septic tanks,
poorly managed sewer pipes and disposal of solid wastes. In addition, groundwater in areas of
intensive washing activity has severe contamination problems. An investigation using nitrate
nitrogen and oxygen isotope concentrations to trace sources (Nakamura et al., 2010) also reported
that human waste is the major source of nitrate contamination in the shallow groundwater of
Kathmandu. This study also revealed that significant differences existed in contamination levels
based on the type of groundwater source (dug wells, stone spouts and tube wells), which was also
reported in other work. Dug wells and stone spouts were the most contaminated with bacteria and
nitrate due to anthropogenic activities.
Acknowledgements Thanks are given to the editor(s) and reviewer(s) whose comments and
suggestions have significantly contributed to the improvement of this manuscript. The first author
is very grateful to Dr Jake Peters for his editorial review and comments on the manuscript.
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