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Plot 4, Lenyadri society, Sus road, Pashan, Pune-411021.
Phone: +91-20-25871539
Email:
Website: www.acwadam.org
acwadam@vsnl.net
Advanced Center for Water Resources Development and Management
ACWADAM
Technical Repor
RAPID GEOHYDROLOGICAL APPRAISAL OF
PURAINEE AND ORLAHA VILLAGES
SUPAUL DISTRICT, BIHAR
with special emphasis on
drinking water management
August 2009
t
Conducted for
Owner Driven Reconstruction (ODR) Collaborative
Technical Report: ACWA/2009/H-MPA 1
Rapid Geohydrological Appraisal of Purainee and Orlaha villages, Supaul
district, Bihar, with special regard to drinking water management and
alternative sources
Conducted for
Owner Driven Reconstruction (ODR)
Collaborative
Advanced Center for Water Resources Development and Management
Plot 4, Lenyadri society, Sus road, Pashan, Pune-411021.
Phone: +91-20-25871539
Email: acwadam@vsnl.net
Website: www.acwadam.org
ACWADAM
Principal authors:
Himanshu Kulkarni, Devdutt Upasani, Siddharth Patil and Harshvardhan Dhawan
August 2009
Acknowledgement:
ODR Collaborative & Megh Pyne Abhiyan
Contents
chapter 1: Background Page 1
chapter 2: REGIONAL SETTING page 3
chapter 3: OBSERVATIONS page 6
chapter 4: INFERENCES AND RECOMMENDATIONS page 19
chapter 5: BIBLIOGRAPHY page 18
Chapter 1: Background
The role of groundwater in irrigated agriculture is a well-known fact. Groundwater irrigation has played a
central role in enabling rural communities to transition from low-productivity subsistence agriculture to
much more intensive forms of production, during the last century, and especially during the last few
decades. This is a phenomenon that is observed from many parts of the world, but clearly more so in the
changing agrarian economies of South Asia. Nearly 85% of all rural water use in India depends upon
groundwater from aquifers, not just for irrigation needs, but also for their day-to-day domestic supply of
water, the latter often being underplayed in discussions on groundwater.
The more ‘obvious’ role of groundwater in supporting irrigation has implied that many of its other roles
often go unnoticed. Most discussions on groundwater are linked to problems of dryland areas, almost
ignoring its relevance in flood-prone regions such as the Gangetic plains of large parts of Northern India.
In such flood-prone regions, groundwater is commonly the only source of perennial domestic water,
especially for meeting drinking water needs of scattered habitations that dote the flat landscapes. The
problem of during floods leads to difficulties in to established sources in an habitation. In
summer, problems of access are uncommon, but issues pertaining to are surfacing in the
region, with evidence suggesting a strong nexus between groundwater quality and related health problems.
Clearly, in such areas, the quantity of groundwater is of secondary importance as compared to accessing
water. This is proving to be a particular challenge in initiatives undertaken as part of the flood-
mitigation and rehabilitation exercise, especially after the deluges by the Kosi and other rivers in North
Bihar.
Considering the peculiar ‘typology’ of groundwater conditions in the region, and the need to develop
village-based strategies in provision of safe and sustainable potable
supplies, a good understanding of local conditions is necessary to
plan and manage groundwater resources in an area or a village.
Information and data that often drive such strategies, are however
rare in such regions. The absence of basic data and scientific
understanding of groundwater from such regions only increases the
risk society faces in the process of developing sound strategies of
drinking water supply.
The plains of North Bihar are prone to flooding because they form
an integral part of a complex river system, which itself is a part of the
The value of groundwater as a buffer drought and flood risk has been a major factor underlying rapid
development of the resource in recent decades. While global estimates are unavailable, groundwater
development has expanded exponentially in many regions since the
1950s, so much so that Tushaar Shah, an eminent economist and
groundwater scholar, has termed the expansion of groundwater
development as “anarchy”. The impact that this has on the resource
base is only now becoming evident. In many locations, groundwater
resources are under threat with many states of India clamouring for
a formal groundwater legislation. The impacts of over-pumping of
groundwater has led to falling water tables, increased costs of lifting
water, deterioration in quality of water available from wells and
serious health consequences like fluorosis and arsenicosis. The
variability in conditions controlling the accumulation and
movement of groundwater, combined with the lack of a solid
scientific understanding of mobilization dynamics, makes it difficult to forecast the impact of
development on groundwater quantity and quality, raising basic questions on sustainability.
excess access
water quality
good quality
1
Ganga river basin. The region is part of what is called the . Hydro-meteorology, river
morphology, neotectonics and afforestation of the sources areas are the main factors influencing flooding
in the region. Rivers such as the Kosi, Gandak, Budhi Gandak and Bagmati run in spate almost each year
and inundate large regions in North Bihar, causing misery to millions and resulting in loss of life, damage
to infrastructure and displacement of communities. The floods of 2007 and 2008 were especially
devastating with rehabilitation work still under progress. The rehabilitation mainly includes construction
of robust houses and the process of setting up a sustainable and safe drinking water system in the villages
of Bihar.
is an initiative by a group of organisations aiming to develop improved alternatives of
drinking water supplies in the flood-prone regions of North
Bihar. What has begun as an initiative during the peak distress
flood period has matured into a much broader initiative looking
into drinking water supplies, keeping the
of communities in mind. The MPA initiative in two
villages - Purainee and Orlaha, Supaul district - includes
developing a strategy for drinking water, a strategy based on
understanding of water sources and their characteristics.
These characteristics include quantitative and quality aspects,
especially in the backdrop of the physical setting, including the
flood-vulnerability of the areas within which these villages are
located.
Most villages in the region of North Bihar depend upon groundwater for their domestic supply, including
drinking water. The proliferation of the - a locally designed hand-pump assembly that fits into a
shallow or deep ‘augured’ hole - has meant easy access to water in a
village. There are chapakals for groups of households, or even more
than one for a single household. The , which used to be the
traditional water access mechanism, has gone out of use. At the
same time, dug wells remain unused but in place, in many villages.
What then is the status of groundwater under this scenario? It is a
well known fact that groundwater conditions tend to vary greatly,
both spatially and over time, in any area. As a result, a good
understanding of local conditions becomes necessary to plan and
manage groundwater in a village. Data that feed into such planning
are seldom available and groundwater management remains largely
constrained as the in large parts of India,
especially in regions such as North Bihar, remains a blank.
MPA, a member of ODR Collaborative, is attempting to fill in parts of this domain, mainly through
extensive water quality monitoring of sources, many of them tapping groundwater, in order to identify the
main challenges in the provision of safe and secure drinking water. It is during this endeavour that MPA
contacted Advanced Center for Water Resources Development and Management (ACWADAM) for
technical capacity building support. ACWADAM has been interacting with MPA and made a
reconnaissance visit to some of its project areas in the summer of 2009. As a first step in developing a
concrete partnership, MPA’s programme co-ordinator attended ACWADAM’s basic training on
groundwater in Pune in July 2009. The visit by ACWADAM in August 2009, was specifically to develop
strategic steps in the management of groundwater resources in Purainee and Orlaha villages. This report is
the result of a quick appraisal of the geohydrological conditions in these two villages, but also attempts to
use findings in these two villages to strengthen MPA’s work in other villages of Supaul as well as the other
districts of North Bihar.
Himalayan foredeep
ODR Collaborative
risk free, sustainable flood
vulnerability
micro-
level
chapakal
dug well
information domain
2
RIVER TOTAL LENGTH in
km
TOTAL CATCHMENT
AREA in km2UPLAND / PLAINS
AREA RAT IO
Gandak 625 45035 3.33
Kosi 736 59503 5.31
Burhi Gandak 431 13191 0.00
Baghmati 330 8439 0.68
Kamla-Balan 266 11347 0.19
Chapter 2: Regional Setting
Study area: Location in context to regional hydrology
Purainee and Orlaha are flood affected villages in North Bihar. Purainee is located within Basantpur
tehsil, while Orlaha is part of Triveniganj tehsil; these tehsils belong to Supaul district, located in the
north-central part of Bihar. Both villages can be approached by road from Patna, via Khagaria-Saharsa-
Madhepura. Purainee is located close to the border between India and Nepal, within close proximity to
the town of Birpur. Orlaha is located close to its tehsil headquarters, i.e. Triveniganj.
Purainee and Orlaha represent the of thousands of villages located in the North Bihar Plains.
The physical setting of the region is defined by clearcut boundaries - the northern linear boundary of the
Himalayan Siwalik foothills and the southern boundary of the meandering Ganga. The North Bihar
Plains are said to cover an area of about 52500 km . These plains are mainly characterised by what is
currently called a “megafan”, or in more common terms, an ‘inland delta’. The overall slope regime for
the region changes from SE in the west to South in the east. The (ox-bow lakes) and (abandoned
river channels or palaeo-channels) are important local-level features that influence water behaviour in the
region. The North Ganga plains have been further sub-divided into a number of units based on fluvial
geomorphology. Of this division, the particular areas of this study are located within the Gandag-Kosi-
Mahananda interfluves, regions subjected to frequent shifting of river channels and floods.
The catchment characteristics of the North Bihar Plains have been presented succinctly by Mahadevan
(2002). A summary table, based on their study is presented here.
micro-setting
tals chaurs
2
3
RIVER Length to Catchment Area
Ratioinkm/km
2Relevance
Gandak 0.014
Kosi 0.012
Relatively higher flux of water and
sediment load
Burhi Gandak 0.033
Baghmati 0.039
Kamla-Balan 0.023
Relatively lower flux of water and
sediment load
The length to catchment area ratios for Gandak and Kosi are much smaller than those for the remaining
rivers, implying that greater fluxes of water and sediment loads are involved in case of these two basins;
this, in simple terms, implies that the risk from flooding by these two rivers (including the stresses on
structures like embankments) will be greater. This analysis also points to the fact that the dynamics
4
involved in deposition of sediments from these two rivers is also quite complex; hence, various
combinations of clay-sand-gravel sequences are likely to be found in these two river basins. Both Purainee
and Orlaha are part of such systems, and even before venturing into surveys in these two villages, it was
understood that the sedimentation sequences in these two locations, especially at the shallow levels, would
be quite complex.
While much of the regional architecture of the North Bihar
flood plains is determined by the main rivers, including the
Kosi, numerous interconnected minor channels participate in
carving out features of the plains by reworking and
redistributing sediments deposited by the main rivers and their
tributaries. The overall system of river alluvia in the region can
only be estimated to be of the order of thousands of metres
thick, especially when one considers that the Kosi alone carries
a sediment load of 130 million cubic metres annually.
Overbank sedimentation is common to the region. This implies
sediments deposited during and after the flood episodes during
which river banks overflow and there is progressive of the banks. This is especially important in
context to development of aquifer systems in the region. As Mahadevan (2002) sums up in his narrative:
“...the Gandak-Kosi interfluve region exhibits a fining upward grain size distribution bottoming in sand or
silt and interleaved with beds of coarse silt and sand; sediments show post-pedogenic alterations including
decomposition of plant and shell material, carbonate dissolution and precipitation,
accumulation and illuviation of clays”. Such sediments usually constitute the host-regime for groundwater
accumulation and movement and aquifers are developed as a consequence of the geometry of overbank
deposits. An understanding of such deposits becomes important in understanding groundwater
accumulation, movement and quality, especially in context to the small and large habitations located in
the region.
A variety of factors affect the resilience and vulnerability of deep (unconsolidated) sedimentary
groundwater systems. The main ones are:
In general, deep sedimentary basins represent a myriad of physical
and chemical dynamics. Distinctions between individual “aquifers”
are often unclear, and experts often differ in the way they identify units for monitoring and analysis. It is
now a well known fact from well-studied deep alluvial aquifer systems that the physical ability of users to
continue pumping for long periods of time (often several decades) despite declines in water level and
water quality creates long-term irreversible changes to such systems; such changes often take longer periods
building up
1. that the volume of water in storage within deep sedimentary basins generally is many orders of magnitude larger
than the annual volume of flow;
2. the complex changes in water chemistry and flow patterns that generally
occur with natural and human-induced changes such as frequent floods,
extraction patterns and the overall development in the region;
3. the large scale of such aquifers – most deep sedimentary basins underlie
large areas and, thus, are subject to a variety of uses and are affected by
decisions occurring across numerous administrative units (districts, states
and even country boundaries);
4. that, in many regions, the temporal scale on which recharge and
discharge from such aquifers occurs is unique and may involve orders of
magnitude of years.
iron oxide / hydroxide
Groundwater occurrence in deep alluvial systems
5
to manifest themselves. In simpler words. deep alluvial systems are not “self-limiting”. Users can continue
to pump long after aggregate extraction exceeds aggregate recharge. Some of the changes that can occur as
a result of this, such as land compaction and quality declines, may be irreversible. Second, basin water
balances are often poorly understood. Major components in the basin water balance, such as
evapotranspiration by native vegetation and deep groundwater flow patterns, are difficult to measure with
a degree of accuracy. As these can be major components of the basin water balance, the lack of
information on them undermines the utility of water balance estimates, even in systems where there is no
pronounced use of groundwater resources.
Hence, most significantly, due to the complex nature of flow regimes within such systems and the
difficulties inherent in defining hydrological boundaries, it is often difficult to attribute changes in
groundwater conditions to changes in use within specific areas as a consequence of natural and human-
induced fluxes. It is also difficult to understand specific recharge mechanisms for a small area. While
upper unconfined systems may receive direct contributions through vertical recharge from precipitation or
return flows from overlying use, lateral flows from streams and other sources are usually significant,
especially in determining groundwater quality. In many situations, surface and groundwater systems are
linked in complex ways with, for example, some sections of a stream either gaining or losing water from
and to groundwater respectively.
This has major implications for the viability of
regional attempts to increase recharge, such as those occurring as part of the water harvesting movement
in India. Basic questions on what a body of ponded water actually serves as – a percolation tank, an
evaporation pond or an irrigation tank – are seldom understood, their utility falling under the general
categories of “water harvesting” and “water conservation”. Finally, water quality dynamics become
complicated with changes occurring as different formations are tapped and as
flow patterns evolve with development.
Particularly in case of the deep confined and semi-confined systems, groundwater
is often released owing to compression of the aquifer material.
Methodology
The current study was undertaken keeping in mind the hydrogeological
complexity of deep alluvial systems and the flood-context of North Bihar.
Inputs to this study were generated from three main sources:
1. Field observations and limited measurements in the villages of Purainee and
Orlaha.
2. Discussions with members of ODR collaborative involved in rehabilitation
work including MPA partners.
3. Primary data on water quality analysed by MPA from the other five panchayats of the district.
Field observations were limited to observing surface exposures, stream cuttings, excavation sections and
one test hole drilled for collecting sub-surface samples (as part of the foundation planning for
construction in Purainee village). The other component of the field work involved opening the head-works
of representative (hand pumps) to record water levels and depths. This enabled plotting water
levels in the form of contours. During the earlier visit (May 2009), qualitative mapping of from
different parts of both villages was undertaken through MPA; this distribution was compared to the water
level distribution measured during the current visit to understand if there was any correlation between
groundwater movement and water quality (especially iron distribution).
Fieldwork included use of instruments such as GPS, geological compass, tape measures and water tracers.
Compilation of data and analysis was done at ACWADAM’s office, using appropriate software. The
report was compiled at ACWADAM’s office after returning from the field and analysing the data
collected. The following chapter highlights salient observations and inferences from this study.
chapakals
iron
Chapter 3: Observations
Topography and drainage
The topography in both the villages seems quite flat. However, there are gentle gradients even at the scale
of the village. Figures 3.1 and 3.2 show 3-D surfaces of the topography in the two villages. In Purainee, the
land slopes gently to the west and southwest, towards the stream located on the western margin of the
village. The village itself is located around two mounds, on the eastern extremity, one in the north and the
other in the south. In Orlaha, the village centre is on higher ground, with the land sloping gently
outwards, in all directions. Topographic gradients are relatively gentler northwards and southwards. A
canal flows along the western extremity of the village. The topography of the village, although magnified
in the diagrams, is too gentle to support drainage lines (streams). Due to the loose, unconsolidated nature
of the material (and much of it is sand or silt on the surface, in both villages), a large proportion of the
rain falling on the ground is likely to infiltrate, although whether it recharges aquifers below, is another
question.
6
Fig. 3.2
Orlaha: Topography
(vertical scale enhanced)
Fig. 3.1
Purainee: Topography
(vertical scale enhanced)
N
N
7
Geology
It would be difficult to completely do justice to the complex geology at both sites. Moreover, this study was
only a rapid appraisal of the two sites, and hence, only observations of direct relevance to the immediate
need of ascertaining the groundwater conditions on a level are given below.
Light coloured sand marks the surface of the ground in Purainee. The sand, clearly shows the presence of
micaceous material, some of which is dark coloured. The presence of sand on the surface is reported to be
sand brought along with flood waters that entered the village during the Kosi deluge of 2008. In Purainee,
it was possible to undertake some sub-surface on the basis of shallow pits dug for construction and
mainly also, on the basis, of samples collected from a 24 foot test hole drilled under a housing project in
the village. The description of these samples is given below, in the form of two illustrative tables.
Table 1 is a for the excavation pit of the foundation of one of the house-construction sites in
Purainee. Table 2, on the other hand, is the compilation of the in Purainee. The
shows that the sediments in the uppermost 1.5 m show a fining upward sequence, topped by silt or
fine sand. The salient feature of the log is a clay horizon at 0.5 m below ground level - bgl (bearing a
consistent thickness of about 0.2 m), wherein the clays swell after saturation and preclude major
infiltration. The clays are underlain by silt at about 1 m bgl. The pit bottoms out with lighter
coloured sands.
Table 2 shows the , which can be broken up into three main sections. At the shallow level
(0 to 4 m bgl), it is dominated by clays, followed by dark coloured, relatively finer sand, which is followed
by coarse, lighter coloured sand, probably with some lenses of (?)finer material. The main water bearing
horizons are likely (from the bore hole log data) to be at 3.5 m and 5.5 m bgl, these two horizons
separated by a layer of finer material.
Both the diagrams show that there are distinct layers of sediment, both in terms of the and ,
the understanding of which would require more elaborate studies. However, a few observations can be
made on the basis of the limited data gathered. In Purainee, the consistent clay layer at a shallow level
indicates some degree of ‘hydrostatic’ pressure, implying at least partial confinement to the groundwater
in the chapakals. Hence, water levels are likely to be representing a potentiometric surface, rather than the
water table of an unconfined aquifer. This, would also have some bearing on the presence of iron in the
chapakals.
generic
logging
shallow pit log
test borehole log shallow pit
log
dark-coloured
test bore hole log
size composition
Purainee
0m
0.4 m
0.8 m
1.2 m
Fine sand / silt
Clay
Dark coloured silt
Sand
Saturated
Fig. 3.3
Log of foundation pit - Purainee
8
0 - 2 feet
2 - 4 feet
6 - 8 feet
8 - 10 feet
10 - 12 feet
12 - 14 feet
14 - 16 feet
16 - 18 feet
18 - 20 feet
20 - 22 feet
22 - 24 feet
4 - 6 feet
(˜0.30 m)
(˜0.92 m)
(˜1.52 m)
(˜2.13 m)
(˜2.74 m)
(˜3.35 m)
(˜3.96 m)
(˜4.57 m)
(˜5.18 m)
(˜5.79 m)
(˜6.40 m)
(˜7.01 m)
24 - 26 feet
(˜7.62 m)
26 - 28 feet
(˜8.23 m)
The upper section includes finer grained material,
dominated by clays. Effect of weathering also
noticed. The dominance of saturated clays at
about 0.5 m bgl implies limited infiltration to
deeper layers.
Coarser material, dominated by sand, with dark
coloured minerals and rock-fragments; micaceous
material apparent. This section corresponds to the
water-bearing horizon.
Finer material, grading downwards into coarser
material. Rock fragments also part of material at
5.18 m (coarsest material in the section). Also
corresponds to water bearing formation, especially
in deepened .chapakals
More consistent sediments, as far as size is
concerned. Mainly sand and some coarser
fragments; grain size decreases below depth of
5.18 m - still mainly in the range of sand-sized
particles.
Fig. 3.4
Borehole log - Purainee
9
Orlaha
Direct subsuface observations, on the lines of the ones made in Purainee, could not be attempted in
Orlaha due to the absence of test pits (foundation work was already complete for most houses) and test
bore holes. However, the overall landscape is flatter, bordered on one side by a canal. The landscape is
probably less obliterated as an effect of the last flood, than in Purainee. Sediments are generally darker
coloured (as appearing on the surface with the dominance of sand). Apart from
this, the regional sedimentation patterns would not be significantly different from
those in Purainee. The subtle differences in the conceptual hydrogeological
model, again based on observations are presented in the following section. The
dominance of sand-sized sediments is obvious, especially based on narratives
captured from discussions with villagers about their .chapakals
Hydrogeology (brief)
In both locations, the hydrogeology (groundwater accumulation, movement and
quality) is controlled by the host sediments - sediments that store and transmit
groundwater. Both the areas are dominated by the presence of river sand, deposited as part of the Kosi
river system. However, given the complexity of the flood regime in North Bihar, there would be several
complex episodes of recycling. However, based on a limited set of observations and from local
villagers, development organisations and other such sources, it is clear that intercalations of clays in
dominantly sand deposits control the behaviour of groundwater, especially at a local level. The geometry
of the interbedded clays, in all likelihood, play a crucial role in the nature of aquifers developed as well as
in the recharge and discharge processes in the region. The current, rather rapid appraisal clearly brought
out the point about local characteristics within an otherwise regional system of groundwater resources.
In order to understand the variability within each site and across the two sites, water levels were measured
in in Purainee and Orlaha villages. Water levels would have normally been difficult to measure
in the , but MPA staff and villagers co-operated by allowing the head-works of representative
to be opened so as to enable water level measurement. Water levels in were measured
along with the locations (latitude, longitude) and elevations (height of measuring point from the mean sea
level). Reduced levels were computed, subtracting the depth to water (water level below the ground, from
the measuring point of each chapakal) from the elevation of the measuring point. These were then plotted
as maps - water level contour maps - to understand the overall groundwater flow system underneath each
village. While measuring water levels, basic water quality parameters were also measured using field-
probes, at some of the sites. These data are presented in the following sections.
The data, plotted as water table contour maps (Figures 3.5 and 3.6) indicate the following:
1. In both locations, despite shallow water levels, distinct patterns of groundwater flow are evident.
2. Groundwater flow in Purainee is ‘from the eastern portion towards the western boundary’. There is a
distinct groundwater mound in the eastern portion of the map, implying that recharge occurs from that
direction. The discharge of groundwater is towards a central line (roughly running east-west through the
middle of the village), with the main discharge zone somewhere close to Jurilal Mandal’s . The
overall pattern of flow lines (red arrows) is indicative of the groundwater flow being part of a more
regional system of groundwater movement.
3. Groundwater flow in Orlaha occurs from a central mound, outwards, mainly in the northerly and
south-westerly directions. The recharge mound is located at the centre of the village and may be part of a
system from the west (from the side of the canal, which was flowing at the time of the measurement).
Hence, the recharge area lies in close proximity to the belonging to Rajendra Mandal and
Ramchandra Mandal. There are two clear discharge areas in Orlaha - one along a north-south line, from
Dhoolan Sardar’s northwards and the other at the southwestern corner, around Jugeshwar
Sardar’s .
narratives
chapakals
chapakals
chapakals chapakals
chapakal
chapakals
chapakal
chapakal
water level
MPA has been conducting water quality surveillance, mainly centred around the testing of and
And although they will be testing for these and other parameters, in some detail, in both the villages
under question, certain interesting patterns of iron (based on a crude methodology picked up by MPA
from experienced locals) emerged during a exercise conducted by MPA, during
ACWADAM’s visit to these two villages in May 2009. The testing
procedure makes use of
. Surely, this
needs to be cross-checked with formal water quality testing;
nevertheless, we developed a crude classification from a systematic
process (testing by the ‘lataam’ method of representative samples from
different chapakals in these two villages, and plotting them onto a map,
based on the GPS readings recorded for different . These maps
are presented as figures 3.8 and 3.9. It may be noted that the
concentrations are ; ad-hoc values, based on the ‘guava leaf’
testing were generated for the plot - with darkest colour having higher
values and ligher shades indicating lower values.
The distribution of iron in Purainee shows decreasing concentrations
towards the southwestern part of the village. The maximum
concentrations are noticed along the northern border of the village.
The distribution pattern of iron in Orlaha reveals two - one at
the centre of the village and the other in the southwestern corner. The
minimum values are nearly in close proximity to the maxima, one in
the north and the other in the southwestern corner. Comparison of
water level data and the iron distribution pattern shows a close
correlation, indicating iron maxima along the main recharge areas,
whereas relatively lesser iron-content is found in association with
groundwater discharge points / zones. And, although this theory needs
to be tested with more rigorous hydrogeology and groundwater quality
surveillance, the broad overlap of patterns would largely remain in
place, at least for the season in which this study was conducted.
Seasonal variability of groundwater flow is expected, but whether such
variability also brings in changes in patterns of iron concentration will
only emerge after continued testing.
The distribution of iron in groundwater conducted by MPA in other
iron arsenic.
participatory testing
crushed leaves of the guava plant - locally called
‘amrud’ or ‘lataam’ - that impart various hues of purple to water contaminated
by iron...the darker the shade of purple, the higher the iron content
chapakals
maxima
not actual
Iron Frequency in Handpumps
80
6
17
21
Above 3
2to3
1to2
Below 1
29
77
Present
Absent
Coliform Occurrence In Handpumps
106 Handp ump samples c hecked
Fig. 3.7: Preliminary water quality results for representative samples
from Supaul district, North Bihar (courtesy: Megh Pyne Abhiyan)
11
10
N
N
Flowlines
Chapakal
Flowlines
Chapakal
Fig. 3.5
Water level surface in Purainee
Fig. 3.6
Water level surface in Orlaha
parts of Supaul district has shown interesting results. Some of these results have significant relevance to
this rapid appraisal. The salient factors are:
1. A large proportion of chapakals show the presence of iron, sometimes significantly higher than the
permissible limit.
2. Although not many dug wells were tested, the proportion of dug wells showing the presence of iron to
the total number is small, especially when compared to the iron in chapakals.
3. And, although dug wells, which in most villages lie in a state of disuse, are likely to have a significant
proportion of bacteriological contamination, chemically, they seem to be safer; incidentally, chapakals also
show significant proportion of bacteriological contamination, which probably takes place through poorly
maintained head-works.
Chapakal
Chapakal
Fig. 3.8
Spatial distribution of iron in chapakals: Purainee
Fig. 3.9
Spatial distribution of iron in chapakals: Orlaha
N
N
12
Chapter 4: Inferences and recommendations
Brief background to iron in groundwater
Inferences for Purainee and Orlaha
(
Iron is common to igneous rocks found in many parts of the world. Most importantly, it occurs in
practically all sediments in . This clearly means it will be common to areas underlain by sediments,
such as the Kosi sediments of North Bihar. However, if the source regions for sediments has rocks with
high iron content, it is likely that sediments also possess a high proportion of iron. Concentrations can
vary between 1 to 5 mg/l - a common range - falling to 0.1 mg/l in water that is aerated during pumping
or treatment. It is common to find iron in the dissolved form in the more -
groundwater with low pH and high oxygen content. Standing water is more likely to have iron as
compared to flowing water.
In natural groundwater, with low oxygen content, and possessing pH between 6.5 and 7.5, iron is mostly
dissolved as . When oxygen levels are nearly zero, even at a pH of 7, iron concentrations
can be very high, peaking to 50 mg/l. Ferrous ions are unstable when in contact with oxygen; in presence
of air, these ions change to and iron precipitates as oxides and hydroxides. Ferric iron is
unsoluble in alkaline or weakly acidic waters. Aeration of water having a pH between 7 and 8.5 implies
that iron becomes insoluble.
.
The geological observations in Purainee and Orlaha helped draw certain key inferences. These are listed
below:
1. Although water levels in at both locations are shallow, it is expected that the water levels in
Purainee represent certain hydrostatic pressure (Fig. 4.1) and recharge to the aquifer is from a location
that is actually outside the boundaries of the village. In Orlaha, the limited observations indicate that
water levels represent a phreatic surface (unconfined), wherein the water table is approximately at
atmospheric pressure (Fig. 4.2). The recharge zones are in close proximity to (perhaps even within) the
village.
2. The fact that most have iron content and dug wells do not, points to the fact that reducing
conditions prevail in chapakals as compared to conditions in wells, where a certain amount of aeration
takes place.
3. Although it is difficult to state convincingly on the
basis of limited observations and data, in all likelihood, discharging groundwater is likely to encounter
oxidation conditions, leaving it with lesser iron than when the water levels lie slightly beneath the surface
(Figs. 4.3 and 4.4).
based on Driscoll, 1986)
traces
corrosive groundwater
ferrous (Fe++) ions
ferric (Fe+++) ions
Sudden changes from the ferrous (dissolved) to ferric (semi-solid) state creates major
problems concerning iron in groundwater
chapakals
chapakals
Most chapakals showed a low dissolved oygen (DO) count.
13
PHREATIC GROUNDWATER
Clay
Sand
Water table
Sand
Sand
Clay
CONFINED GROUNDWATER
Potentiometric surface
Fig. 4.1: Conceptual representation of groundwater in Purainee
Fig. 4.2: Conceptual representation of groundwater in Orlaha
14
Fig. 4.3
DO: Purainee
Fig. 4.4
DO: Orlaha
N
N
15
16
Recommendations
The following recommendations are being made with a view to develop a strategy-asetof
, bearing in mind the flood-proneness of the villages as well as the analysis of the groundwater
situation - emerging from this rather rapid study. The strategy, primarily seeks to provide improved
‘quality’ water to the two villages, bearing in mind the context and the situation.
Purainee and Orlaha are located in a flood-prone setting, underlain by thick stacks of sediments brought
by the Kosi river system - sediments that show variation in grain size from clay to coarse sand, even gravel.
These sequences of sediments create complex systems of groundwater occurrence and movement. Water
levels remain close to the surface of the ground throughout the year (needs verification), but there are
gentle gradients to the water level surface, inducing
groundwater movement even under a single village. The
levels of dissolved oxygen are low, implying that reducing
conditions prevail. Consequently, one would expect iron
to be prevalent too. In the absence of large scale sanitation
facilities, the risk from on-site bacterial contamination
remains to be high, especially during the rainy season,
when the thickness of the unsaturated zone within the
subsurface is bound to be at a minimum. With this
background, the following is recommended as a strategy
for Purainee and Orlaha:
1. Monsoon season: Rainwater harvesting
Sub-surface storage, including groundwater recharge to be
avoided. Harvested rainwater should be used during the monsoon, and especially during floods.
2. Winter and summer seasons: The dry season, following the monsoon could be a transition from using
harvested rainwater to using dug well water. The areas which are likely to yield safe water (quantity and
quality) for a dug well have been indicated in figures 4.3 and 4.4 for the two villages respectively, based on
the geology, distribution of water levels, patterns of iron variability and dissolved oxygen. The exact site
may be decided through a participative process involving the community in both villages.
3. It would be a challenge to move people from using to using dug well water, especially during
the dry season, as access to water is rendered easy with the . However, a simple protocol of
collecting water from a dug well and storing it at the household level - only for drinking - could be
initiated. For other uses, use could continue...
4. Detailed water quality monitoring in both the villages would further consolidate the recommendations
made here, even yielding a higher degree of specificity to the location of dug wells.
water use
actions
above the ground.
A practice
of using it as drinking water is already being promoted and there are positive vibes from the community in this regard...
chapakals
chapakal
chapakal
17
Fig. 4.5
Purainee: Site for community dug well(s)
Fig. 4.6
Orlaha: Site for community dug well(s)
N
N
Area for dug well construction
LEGEND:
18
BIBLIOGRAPHY
Shah, T. 2009. Taming the Anarchy: Groundwater Governance in South Asia. ,
Washington D. C. 310p.
Sinha, R. and Jain, V. 1998. Flood hazards of North Bihar rivers, Indo Gangetic plains.
v 41, pp. 27 - 52.
Sinha, R. and Friend, P. F. 1999. Pedogenic alteration in the overbank sediments, North Bihar Plains,
India. . v. 53, pp. 163 - 171.
Resources for the Future
Mem. Geol. Soc.
India.
Jour. Geol. Soc. India
ACWADAM. 2001. Thematic mapping of ravine lands in the Karaondia – Sengur – Yamuna confluence
system, Bhognipur tehsil, Kanpur (Dehat) district, Uttar Pradesh, using Remote Sensing and GIS :
With special emphasis on geohydrological studies. For BAIF
Dev. Res. Foundation.
Driscoll, F. G. 1986. Groundwater and Wells, 2nd Edition. Minnesota, 1108 p.
Gohain, K. and Parkash, B. 1990. Morphology of the Kosi megafan.
(referred to in Mahadevan,
2002).
Mahadevan, T. M. 2002. Geology of Bihar and Jharkhand. , Bangalore. 563p.
Parkash, B. and Kumar, S. 1991. The Indo Gangetic basin.
. Gyanodaya Prakasam, Naini Tal, India. pp. 147 -
170.
ACWADAM Tech. Report 2001/H-3.
Johnson Division,
In: Alluvial fans, a field approach:
Rachocki, A. H. and Church, M. (eds.), John Wiley and Sons Ltd. pp. 151 - 178
Geological Society of India
In: Tandon S. K., Pant, C. C. and Kashyap, S. M.
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