Preprint - do not cite - 1 A Review of Groundwater status, challenges, and 1 research needs in the Kathmandu Valley, Nepal 2 3 Soni M. Pradhanang 4 City University of New York, Institute for Sustainable Cities, New York, NY, USA 5 [email protected]6 7 Suresh Das Shrestha 8 Tribhuvan University, Department of Geology, Kathmandu, Nepal 9 10 Tammo S. Steenhuis 11 Department of Biological and Environmental Engineering 12 Cornell University, Ithaca, NY, USA 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Corresponding Author: 36 Soni M. Pradhanang, City University of New York, Institute for Sustainable Cities. New York, 37 NY, [email protected]38 39
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Preprint - do not cite - 1
A Review of Groundwater status, challenges, and 1
research needs in the Kathmandu Valley, Nepal 2
3
Soni M. Pradhanang 4 City University of New York, Institute for Sustainable Cities, New York, NY, USA 5 [email protected] 6
7
Suresh Das Shrestha 8 Tribhuvan University, Department of Geology, Kathmandu, Nepal 9
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Tammo S. Steenhuis 11 Department of Biological and Environmental Engineering 12 Cornell University, Ithaca, NY, USA 13
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Corresponding Author: 36
Soni M. Pradhanang, City University of New York, Institute for Sustainable Cities. New York, 37 NY, [email protected] 38
3 Drinking water quality and quantity has been one of the biggest concerns in water sector in The 4 Kathmandu Valley, the biggest urban center in Nepal. Aquifer characteristics and groundwater 5 flow properties are complex. They vary laterally and, vertically and temporally creating 6
dynamic, interdependent systems that can be affected in unpredictable and irreversible ways as a 7 result of rapid development and mismanagement. Over extraction of groundwater in the Valley 8 has resulted in groundwater depletion. The problems related to groundwater quality range from 9 contamination from sewage line, septic failures, and open pit latrines, leaching from landfill 10 sites, and direct disposal of domestic and industrial wastes to the surface water. Studies have 11
shown that both the quantity and quality of groundwater in The Kathmandu Valley is in immense 12 threat that needs immediate attention. The research, development and management of 13
groundwater resources are still emerging. Priorities need to be set up for effective mapping and 14
monitoring of this resource by developing research and management plans. The goal of this 15
paper is to summarize status of groundwater quantity and quality, challenges and research needs 16 in The Kathmandu Valley based on available literature. 17 18
19 20
21
Keywords: Aquifer, extraction, water quality, mapping, development. 22
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1. INTRODUCTION 1
Groundwater resources play a major role in ensuring livelihood security across the world and 2
can provide a uniquely reliable source of high-quality water for human uses. Not all groundwater 3
is accessible. In many cases it is too deep or too salty to be used. In other case the ground water 4
is soils with little permeability. In cases that groundwater is available; it is perceived by many, as 5
inexhaustible resource. Therefore, in many places in the semi arid and arid areas of the world, 6
ground water tables are dropping with rates of 1 meter per year or more. Base flows in streams, 7
wetlands and surface vegetation are in many cases dependent on groundwater levels and 8
discharges. Change in those levels or changes in groundwater quality induce cascading effects 9
through terrestrial and aquatic ecosystems. In China, for example that had once many beautiful 10
rivers, ground water withdrawal caused these rivers to disappear or in some cases are filled with 11
the waste water from the cities. The same is true for Kansas, USA where rivers are starting to 12
disappear. 13
The ability to access groundwater plays a major role in increasing incomes and reducing 14
risks in agricultural economy (Moench et al., 2003). The depletion of groundwater is taken as a 15
first indicator of water scarcity (Shah and Indu, 2004). Drinking water quality and quantity has 16
been one of the biggest concerns in water sector in Kathmandu Valley, the biggest urban center 17
in Nepal (Cresswell et al. 2001; Pathak et al. 2009). The Kathmandu valley covers about 327 18
km2 of 664 km
2 surface watershed areas in the central Nepal with average altitude of 1350 m 19
above mean sea level. Annual precipitation in the valley is around 1755 mm, 80% of which is 20
from monsoon rain that spans from June to September (Pandey et al. 2010). Recharge to the 21
region’s main aquifer has been variously reported to be 15 million m3/yr (i.e., 165 mm/yr) 22
(Binnie and Partners 1989) to less than 5 million m3/yr (i.e., 55 mm/yr) (Gautam and Rao 1991). 23
Recharge to the deep confined aquifer, however, is suggested to be < 80,000 m3/yr (1mm/yr) 24
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(Gautam and Rao 1991).The study by CES (1992) reported that almost 50% of the valley’s water 1
supply is derived from groundwater. The extraction rate is reported to be 20 million m3/yr. 2
Large inconsistencies in reported recharge and extraction rates warrant a standard protocol of 3
research. 4
The problems related to groundwater range from contamination from sewage line, septic 5
failures, open pit latrines (Jha et al. 1997), leaching from landfill sites, and direct disposal of 6
domestic and industrial wastes to the surface water (Khadka 1992; Karn and Harada 2001). 7
Surface water in Kathmandu Valley is highly polluted due to unregulated disposal of domestic 8
and industrial wastes. Such haphazard waste disposal systems cause contamination of shallow 9
aquifers. About 50% of the water supply in KTM is from groundwater systems that consist of 10
both shallow and deep aquifers (Jha et al 1997; Khatiwada et al. 2002). Variety of systems such 11
as tube wells, dug wells, and stone spouts constitute major mechanisms of groundwater use, due 12
to insufficient supply of surface water for both drinking and non-drinking uses. These systems 13
are also known to be contaminated by pollutants and pathogens (Table 1). 14
The population of KTM valley in 2001 was 1.6 million with a projected growth rate of 15
5% (MOPE, 2000; ADB, 2004; Dixit and Upadhyaya 2005) (Figure 1). Various other 16
organizations have different projections for the population of the Valley. After the inception of 17
municipal system in 1970s, which promoted use of surface water and deep aquifer tube wells and 18
shallow wells, many communities abandoned other sources of water which include traditional 19
stone spouts, dug wells and shallow aquifer tube wells (Khadka 1993; Warner et al. 2008). 20
However, the study conducted by Brown and Watkins (1994) reported that almost 20% of the 21
population of greater Kathmandu still rely on stone spouts during much of their year for their 22
water supply. 23
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Year
1990 2000 2010 2020 2030
Po
pu
lati
on
in
mil
lio
ns
0.0
2.0
4.0
6.0
MOPE Census
BDS Design
SAPI Phase II
KUKL service area
1
Figure 1. Population census and projection for Kathmandu Valley [ Kathmandu Valley Census and 2 Projection (MOPE, 2000); Bulk Distribution System (BDS) Design Projection ; Special Assistance for 3 Project Implementation (SAPI) Phase II Projection; and Kathmandu Upatyaka Khanepani Limited 4 (KUKL) service area (~650 sq. km).[Source: ADB (2006)]. 5
The water demand of increasing population cannot be met by current supply from municipal 6
corporations (Dixit and Upadhyaya 2005). The inadequate and inefficient supply systems of 7
municipal corporations have led the population at large to supplement their water supply by 8
tapping into traditional water sources, i.e., stone spouts (Shrestha et al. 1996). Unfortunately 9
many stone spouts are now converted into temporary refuse dumps that need proper 10
rehabilitation. 11
The objective of this article is to present current status of groundwater both quantity and 12
quality, in Kathmandu Valley based on available literature and reports. Compilation of past 13
researches, methodologies and major findings that are relevant to ground water systems in 14
Kathmandu Valley is presented in Table 1 and discussed in following sections. 15
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2. VULNERABILTY ASSESSMENT 1
2
The groundwater of Kathmandu Valley is under immense pressure as it is being heavily 3
utilized for both drinking and non-drinking purposes. Although groundwater overexploitation is 4
recognized as a serious problem (Cresswell et al. 2001), until mid 1990s, ground water resource 5
development received greater attention. The approaches of ground water resource development 6
coupled with monitoring, management and research is still developing. There are number of 7
researches that address the potential impacts of groundwater overuse on both quantity and 8
quality (Table 1), however, such researches are usually bound through contractual agreements to 9
keep data confidential from public access. Availability of such information will not only help to 10
develop scenario on groundwater use spatially and temporally, but also allow researchers to 11
evaluate vulnerability of groundwater usage addressing availability and water quality. Potential 12
dangers to drinking water sources, water quality and its availability are some indicators that are 13
considered for this study. 14
2.1 Mapping Groundwater Resources: 15
Conventional approaches to understanding groundwater resources involve geological 16
provinces describing broad physical characteristics of regional geological systems. These maps 17
describing the physical settings in which groundwater accumulates and modes need to be further 18
disaggregated to make them useful for local situations. The first step to understand the 19
vulnerability of groundwater system is to develop boundary maps and identify potential problem 20
areas. 21
Within the unconsolidated sediment of the Kathmandu Valley, there are two major aquifers 22
that provide locals with potable drinking water (Figure 2). The upper aquifer is composed of 23
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quaternary arkosic sand, with some discontinuous, interbedded silt and clay of the Patan and 1
Thimi Formations (Yoshida and Igarashi 1984). The surficial sediments that compose the upper 2
aquifer are underlain by an aquitard of interbedded black clay and lignite that reaches up to 200m 3
in thickness in the western valley. The Pliocene sand-and-gravel, with interbedded lignite, peat 4
and clay lies beneath the clay aquitard and constitutes the deeper confined aquifer used by 5
several hotels, private companies and municipalities (Jha et al. 1997). 6
7
Figure 2. Map of Kathmandy Valley showing geological formation and ground water districts. 8
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Table 1. Some relevant peer reviewed literature on Groundwater studies in The Kathmandu Valley. 1
Authors Objective of Research Methods Major Findings
Cresswell, R. G et
al., 2001
Quantification of groundwater
recharge rates and residence times
Radioisotope study Current recharge rate is about 5 to 15 mm/year
contributing 40,000 to 1.2 million m3/year to
the groundwater. Current extraction rate is 20
times of this amount and reserves will be used
up within 100 years at current rate of
extraction.
Dixit A. and
Upadhya M. 2005
Summarize existing knowledge on
groundwater conditions and identify
potentials for development
Compilation of relevant literature
and analysis
Substantial opportunity may exist for increasing
municipal supplies by conjunctive management
of surface and groundwater sources including
direct and indirect recharge and rainwater
harvesting.
Pattanayak S K.
and Yang J-C.
2005
Test the coping costs and stated
preferences for willingness to pay
for improved services
Household Survey of 1500
randomly sampled households;
develop profile of sample
households.
Coping costs arise from behaviors such as 1)
collecting, treating, storing and purchasing, 2)
are equivalent to 1% of current incomes, 3) are
lower than the willingness to pay, and 4) vary
across household with different socio-economic
backgrounds.
Villholth K G. and
Sharma B. 2006
Present major issues related to
groundwater in South and South
East Asia
Summary of literature To tackle the problem of groundwater
depletion, there is a need to integrate
environmental, social and economic factors
Effective groundwater resource management
requires an optimum balancing of the
increasing demands of water and land users
with the long-term maintenance of the complex
natural resource.
Gurung, J. et al.,
2007
Examine geochemistry of the
Kathmandu aquifer sediments, the
elution behavior of arsenic(As) and
evaluate the mechanism causing
mobilization of As in groundwater
Elution analysis to determine
potential leaching of As from the
aquifer sediment
Arsenic concentration in the sediments of
Kathmandu Valley average 8mg/kg, similar to
typical modern sediments (5-10mg/kg). The
mobilization of As in the Kathmandu Valley is
mainly related to change in the redox
conditions resulting from iron oxide rich sediment along with high organic content.
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Table 1. Contd…
Authors Objective of Research Methods Major Findings
Kannel et al. 2007 The assessment of variation of water
quality, classification of monitoring
networks and identification of
sources
Water quality analysis of
important physical, chemical and
biological parameters
Upstream river water qualities in the rural areas
are affected mostly due to sewage disposal and
transport of fertilizers and manure applied to
agricultural fields. Urban water is mostly
polluted due to untreated municipal sewage and
can have impacts on shallow aquifers.
Warner et al. 2008 Identify common drinking water
contaminants; compare water quality
between sources; evaluate
relationship between water quality
parameters and site characteristics.
Water sampling (115 samples)
prior to monsoon season and
laboratory analyses for bacterial
contamination, inorganic
pollutants and heavy metals;
Household surveys using
questionnaire; statistical analyses
using non-parametric statistics.
Pathogens (coliform, both total and fecal) were
found in 72% of the water sampled. Nitrate-N
and ammonium-N exceeded the Nepali
guidelines for 45% of the samples, arsenic and
mercury exceeded WHO standards for 10% of
the samples.
Pathak, D. R. et
al., 2009
Development of groundwater
vulnerability map
GIS based DRASTIC model;
sensitivity analysis
The GIS based aquifer vulnerability map was
developed which is used to reflect an aquifer’s
inherent capacity to become contaminated
based on pollution index. The resulting range of
groundwater pollution potential index values
extended from 59 to 205. The vulnerability
index of Kathmandu indicated high
susceptibility to contaminations.
Chapagain et al.,
2010
Assess the current state of water
quality and identify the major
factors affecting water quality of
deep groundwater in the Valley
both.
Physico-chemical analysis of
major cations and anions;
Principal Component Analyses,
Factor Analyses and Cluster
Analyses of all water quality
parameters.
The groundwater in the valley is classified as
Ca-HCO3 and (Na+ K)- HCO3 types with
concentration of NH4+-N, Pb, As, Fe, Cd found
at most of the sampling locations. Water quality
of deep groundwater is affected primarily
related to hydrogeochemical properties and less
to the human activities.
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Table 1 Contd…
Authors Objective of Research Methods Major Findings
Kannel et al. 2010 Evaluation of seasonal variations of
water qualities of Bagmati River.
Multivariate statistical analysis Seasonal variation in water quality were observed
especially for parameters such as, temperature,
DO, EC, COD, Cl, Ca, alkalinity, PO4-P,and TP.
Pandey et al., 2010 Develop a systematic knowledgebase
of the Kathmandu Valley’s
groundwater environment by
separating both natural and social
systems, analyzing their extent and
interrelationships.
Indicator that reflect valley’s
groundwater environment based on
review of published and
unpublished reports, papers, and
data.
The indicators show that the anthropogenic
factors are major drivers that exert pressures on
groundwater environment. Over-exploitation of
groundwater has lowered the groundwater levels
and raised concerns on risks of land subsidence in
area with high compressible clay and silt layers.
Pant B R. 2010 Assess quality of groundwater in the
Kathmandu Valley.
Groundwater samples from shallow,
deep-tube wells from October to
December 2004 were analyzed for
physical, chemical and biological
properties.
The groundwater in the Valley were found to be
contaminated with iron (1.5-1.9 mg/L) and
coliform bacteria (129 CFU/100 mL and 148
CFU/100 mL in tube well and deep well
respectively). Study showed high electrical
conductivity and turbidity.
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Based on the hydrologic formation of various characteristics including river deposits, the
Kathmandu Valley is divided into three groundwater districts(Figure 2) a) northern, b) central,
and c) southern districts(JICA 1990). The northern groundwater district is composed of
unconsolidated highly permeable materials, which are about 60m thick and forms the main
aquifer in the valley. The coarse sediments are interbedded with fine impermeable sediments at
many places. This area is categorized to have relatively good recharge capacity. The central
district comprises of impermeable stiff black clay (sometimes ~200m thick), along with lignite
deposits and underlying layer of unconsolidated coarse sediment deposits of low permeability.
Existence of soluble methane gas in this area indicates stagnant aquifer condition. This area is
categorized to have low recharge capacity due to thick impermeable layers. The geologic
formations of the southern district consist primarily of thick impermeable clay and low
permeable base gravel. The aquifer in this area is known to be less developed (Pathak et al.
2009). According to the sedimentary development, the area suitable for recharging aquifers is
located mainly in the northern part of the valley and along the rivers. In the southern part
recharge is restricted to the areas along the gravel fans near the hillside. Detailed investigation on
this boundary is necessary or future researches. Until this is fully resolved pumping of this part
of the aquifer should be restricted.
Wide spread silty lacustrine deposits that are usually fine grained control groundwater
recharge for shallow aquifers in the Valley. The aquifer is interbedded with the impermeable
clay and prevents easy access of percolating rainwater to the aquifers. Most of the annual
precipitation falls during monsoon from June to September, but runs off quickly as surface flow
and is not sustained during the dry season. Streams of the Kathmandu valley receive some water
from the shallow aquifer after the monsoon season (Kharel et al. 1998). Recharge of the deep
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aquifer occurs in the northeast part of Kathmandu Valley where the thick confining unit of clay
is not present (Figure 2).
Figure 3. Cross section through the Kathmandu Valley, with vertical exaggeration, adapted from
Jha et al. 1997 and Creswell et al. 2001
Pathak et al. (2009) developed groundwater aquifer vulnerability map by incorporating
the major hydro-geological factors that affect and control groundwater contamination. They used
the United States Environmental Protection Agency (EPA) approved groundwater vulnerability
analysis method called DRASTIC (Aller et al. 1987). The maps produced from such researches
are extremely valuable and serve as important resource to begin further impacts and vulnerability
assessments. In addition, such maps may be used for planning and predictive management of
groundwater resources. There are not many works that have focused on delineating groundwater
boundary and mapping of sub-surface groundwater systems. The lack of literature in this regard
is a clear indication that there is a need for research and development of mapping ground water
resources in Kathmandu Valley.
Stagnant Zone
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2.2 Water Resource Issues:
The challenge associated with groundwater resource in Kathmandu valley is that there is
an over-exploitation of the resource in some parts of the Valley, whereas some areas have
relatively low levels of extractions. The study by Metcalf and Eddy (2000) showed that there was
a drop in pumping water level from 9 m to 68 m over the few years. The total sustainable
withdrawal of groundwater from the valley’s aquifers is approximately 0.0263 million m3 /d
(Stanley 1994), and increased to 0.0586 million m3 /d by 2000 (Metcalf and Eddy 2000).
However, it is unclear whether this withdrawal rate is representative of the shallow or deep
aquifers. One might be able to pump a lot from the shallow aquifer if there is sufficient rainfall to
fill up each year, given that the surface has good infiltration capacity.
Pandey et al. (2010) conducted a study to estimate groundwater storage potential in
Kathmandu Valley. They reported that the total extraction was less than 0.04 million m3/yr in
early 1970s, which went up to around 12.2 million m3/yr in late 1980s with another 90% increase
in late 1990s consistent with the findings of HMG (2004) (Figure 4). The study also classified
the period from 1970s to late 1990s as 1) early 1970s as the baseline situation where
groundwater availability was high with less being supplied to the public, 2) early 1980s as the
low impact period with inception of groundwater development and extraction systems, 3) mid
and late 1980s as the period when NWSC started well fields and impacts of extraction became
visible, 4) early 1990s when number of private wells increased and impacts increased, and 5) late
1990s as the period where haphazard pumping occurred resulting in groundwater table to decline
considerably.
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Systems
NWSCHotels
PrivateDomestic
Government InstitutionsEmbassy
Gro
un
dw
ate
r E
xtr
acti
on
(m
3/d
)
0
5000
10000
24000
Shallow well
Deep Well
Dug Well
Figure 4. Groundwater extraction rate in The Kathmandu Valley for different systems from NWSC ( Nepal Water Supply Corporation currently known as Kathmandu Upatyaka Khanepani Limited) to other uses such as hotels, domestic uses, and institutions. [Source: HMG , 2004].
They also conducted a systematic knowledgebase study of the Kathmandu Valley’s
groundwater environment by separating both natural and social systems, analyzing their extent
and interrelationships. Their study concluded that the indicators show that the anthropogenic
factors are major drivers that exert pressures on groundwater environment. Over-exploitation of
groundwater has lowered the groundwater levels and raised concerns on risks of land subsidence
in area with high compressible clay and silt layers. This does not necessary mean that the
pumping should entirely focus on shallow aquifer systems.
Deep tube wells are the main means of extracting groundwater for use in the water supply
system. The study conducted by Asian Development Bank (2004) showed that out of 73 existing
deep tube-wells only ~74% were in operation. Most of the tube wells’ electro-mechanical parts
were considered to be in non operable condition with flow meters missing or broken. Tube wells
were used to be operated only in the dry season in order to supplement reducing surface water
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sources, but, due to demand exceeding supply, the general public is now forced to use this
alternative source of water supply even during wet seasons. Deep wells usually have a very slow
recharge capacity. Further studies need to be done to explore other sources of groundwater
systems.
Table 2. Groundwater storage potential in municipalities of Kathmandu Valley