Ground Water Atlas
Physiography And Drainage
Drought Area
Ground Water Surveys and Exploration
Ground Water Exploration in Purna Alluvial Area
Ground Water Exploration in Tapi Alluvial Area
Lineaments
Hydrogeology
Electrical Conductivity of Ground Water
Quality of Ground Water
Physiography And Drainage
Physiography
Topographically, the entire State of Maharashtra represents an easterly-sloping plateau. The
Sahyadri and the Satpura are the main mountain ranges. From the Sahyadri in the west, which
attains a variable height (600-1646 m. amsl) to the Wardha-Wainganga plain in the east showing
occasional low trends (less than 100 m. amsl), the plateau represents a variety of features. West
of the Sahyadris is a longitudinal coastal strip separated from the Western Ghats by an
escarpment (600 m.) and presents lowlands where the heights range from sea level to 350 m.
amsl.
Thus, the physical features of the state can be grouped under three broad divisions i.e. (i) the
Konkan Coastal Plain, (ii) the Western Ghats and (iii) the Maharashtra Plateau.
The Konkan Coastal Plan
The narrow coastal plain in the west stretches N-S to a distance of about 500 km. The northern
part of this is relatively flat with occasional hillocks. Numerous streams originating on the
Sahyadrian scarp, meander their way to the sea. Around Mumbai, the coast is dotted with a
number of off-shore islands. East of Mumbai, falling in the Ulhas Basin, is a flat plain. This
plain also has some outliers of the Western Ghats, the most well-known being the Matheran hills
(700 m. amsl).
Almost all the rivers originating from the Western Ghats descend to the coast. These are
controlled and guided by fractures and lineaments and forming deep gorge upto 200 m. The
estuaries of these rivers are submerged and the tidal impact is felt as far as 25 km. inland.
The coast is bordered by cliffs. At places, these cliffs are as high as 60-70 m. plunging into the
sea. At other places, littoral terraces or line of dunes occur behind the beach. In the South
Konkan extending upto Sindhudurg district, there are no coastal plains as found in the North
Konkan.
The Western Ghats
The Sahyadris, commonly known as the Western Ghats, represent the western edge of the
Deccan Plateau. Here, the basaltic plateau reaches a height varying from 800 to more than 1600
m. amsl. The western edge of the plateau ends abruptly with an escarpment descending to a
coastal lowland. The escarpment at places is more than 600 m. and looks like a wall. The
Western Ghat escarpment, in all probability, is a fault escarpment. The general height of the
Ghats at the coast ranges between 800 and 1600 m. amsl. However, wherever the crest line is
breached by headward erosion of the easterly-flowing streams, the continental divide lowers
itself to even less than 700 m. (Lonawala). The highest point of the Sahyadris in Maharashtra is
Kalsubai (1646 m. amsl.).
The Sahyadris are the main source of all the major rivers, not only of Maharashtra but the whole
of Deccan Plateau. The most important of these, the Godavari and the Krishna, have their
sources in the. Western Ghats. The river Godavari originates near Nasik while the Krishna near
Mahabaleshwar. A number of off-shoots project from the main axis of the Western Ghats
eastwards. The Sahyadris are reduced to a saddle wherever they have been dissected by
headward erosion of plateau streams and rise to form mountainous high plateaus and peaks
where the projecting spurs join them.
The Sahyadri mountains are also the sites of deep valleys and deep ravines due to which
numerous irrigation and hydro-electric projects have been commissioned. The rainfall is also
high due to which there is luxurious growth of plants and the entire range is covered by forest,
much of it in denuded state.
The Maharashtra Plateau
East of the Sahyadris extends the Maharashtra PI'ateau for a distance of more than 700 km. It
comprises numerous small plateaus and valleys. The main plateau shows declining heights, both
towards the eastern and northern periphery of the State. In the extreme eastern part, especially
east and south of Nagpur, the average height varies from 250 to 300 m. amsl, though occasional
residual hills are as high as 450 m. amsl. The Umrer hills and the Chimur hills, forming the
divide between the Wardha and the
.Wainganga rivers, attain a height of 418 and 450 m. amsl respectively.
The Tapi-Purna valley, an east-west furrow in the Deccan table land, extends over a distance of
more , than 300 km. and shows a variation in height ranging between 200 and 300 m. amsl. The
entire valley is asymmetrical in cross-profile and is covered with alluvium. It stands in sharp
contrast to the barren Deccan plateau in the south and the Satpura hills in the north. The broad
valleys of the Bhima, the Godavari and the Krishna are separated by flat-topped divide which
project eastward from the Sahyadrian Range.
The height of the plateau varies between 450 and 700 m. amsl. The valleys are broad, bordered
by 100 -200 m. high escarpment. Down these escarpments (Ghats) are the Piedmont, gently
sloping areas and merges with the terraces on either side of the streams. Extensive flat-topped
hills are seen everywhere and even major water divides are flat-topped.
Topographically, there are two more areas in Maharashtra which attain considerable heights i.e.
"the Satmala-Ajanta chain" that forms the southern rim of the Tapi trough and the other is "the
Melghat- Gawilgarh hills" which is sandwiched in the Tapi-Purna fork. In the Satmala-Ajanta
scarp face, the famous Ajanta Caves are located. The Satmala-Ajanta chain branches off from
the Saptashringi peak, close to the Sahyadris, with progressively decreasing heights.
The Melghat complex overlooks the Tapi valley in the north and the Purna valley in the south.
The highest point of the plateau is Chikaldara (1016 m. amsl), which, incidentally, is a hillstation.
Drainage
The major part of the state is drained to the Bay of Bengal by two major rivers, the Godavari and
the Krishna and the rest of the part is drained to the Arabian sea by the west-flowing Tapi river
and the Konkan rivers emerging from the Western Ghats and joining directly to the sea.
Godavari
The Godavari basin roughly covers half of the area of the State. The river has 1465 km. length in
the State. The major tributaries of the Godavari are the Pravara, the Purna, the Manjra, the
Penganga, the Wainganga, the Wardha and the Pranhita. A characteristic feature of the Godavari
is its deep channel enclosed between its bank, which are more like embankments and the narrow
alluvial flood plains. The annual discharge of the Godavari at Dhavaleshwaram (in Andhra
Pradesh) is around 1,00,000 mcm.
Krishna
The Krishna river emerges from the Western Ghats near Mahableshwar. It has a total length of
about 1400 km. in the State. The principal tributaries of the Krishna are the Bhima and the
Koyna. The major tributaries of the Bhima, are the Ghod, the Indrayani, the Mula-Mutha and the
Nira. An important feature of the Krishna basin in the State is the enormous amount of
sedimentation. The annual discharge of the Krishna at Sangli is around 14,700 mcm. The earliest
irrigation project named Nira Canal in Maharashtra, was constructed in 1846 in the Krishna
basin on the river Yelwandi at Bhatghar.
Tapi
It is the only large river of Maharashtra joining the Arabian sea. It rises from the Betul Plateau in
Madhya Pradesh. It has a total length of about 724 km. covering an area of about 52,226 sq.km.
which is about 16.96 per cent of the entire state's area. The valley and large plain associated with
it are drained by a number of parallel tributaries which join the main river at right angles, though
in a few cases a downstream bend close to the Tapi is observed. The tributaries of the Tapi as
well as the Purna form an important element in the Tapi-Purna river system. The most important
tributary of the Purna is the Chandrabhaga, which descends from the Melghat Plateau. The other
important left-bank tributaries are the Murna, the Mun and the Nalganga. The most important
tributaries of the Tapi is the Girna which originates from the Western Ghats. The other left-bank
tributaries include the Waghur, the Bari, the Panjhara and the Buray. The Waghur passes
through the Ajanta hills in which the world famous Ajanta Caves are located. The valley-side
slopes as well as slopes on the transverse profile of the entire basin are very steep.
Coastal Rivers or Konkan Streams
The coastal rivers flow east-west roughly parallel to each other and their length is 100 km. Most
of these river courses are structurally controlled. The important rivers of North Konkan are the
Pinjal, the Vaitarna, the Bhatsal and the Ulhas, while the Amba, the Kundalika, the Savitri, the
Vaishishti, the Shastri, the Kajvi, the Waghotan and the Ghod are the principal South Konkan
rivers. The coastal rivers, particularly the ones south of 18°N latitude are deeply entrenched in
the lateritic plateau which has a general height of 200 m. The valley forms in Konkan are greatly
influenced by the laterites which behave like permeable rocks.
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Drought Area
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Maharashtra frequently experiences drought conditions like other parts of the country which
affects agricultural production and economy. Long-term rainfall data (1901-1990) for 90
raingauge stations of the State were used to compute normal rain- fall and the departure of the
yearly rainfall from the normal to study the recurrence of drought and to demarcate droughtprone area of the State.
A period of drought is defined as a year in which the total rainfall is less than 75 per cent of the
normal and accordingly classified as moderate, severe and acute drought where the departure of
annual rainfall range is -25 to -49 per cent, -50 to -74 per cent and more than -75 per cent
respectively. If in an area drought conditions are experienced for 20 per cent or more years, then
the area is classified as drought area and if the frequency is 40 per cent or above, the area is
termed as chronically drought-prone. Climatologically, the State can be divided into four regions
i.e. Konkan, Marathwada, Madhya Maharashtra and Vidarbha.
Konkan
The probability of occurrence of drought of all categories ranges from 8 per cent (Vengurla and
Kudal, Sindhudurg district) to 22 per cent of the years (Dahanu, Thane district). The moderate
drought conditions ranged from 7 per cent (Vengurla, Kudal) to 20 per cent (Dahanu), while
severe drought conditions ranged from 1 to 6 per cent of the years and acute drought conditions
were not experienced in this part of the State. Thus, the frequency of occurrence of drought in
Konkan region ranges from once in 12 years at Vengurla and Kudal to once in four years at
Dahanu.
Marathwada
The probability of occurrence of all categories of drought ranges from 14 per cent (Osmanabad)
to 26 per cent of the years (Parbhani). Moderate drought conditions range from 13 per cent
(Ahmadnagar and Osmanabad) to 23 per cent of the years (Parbhani) while severe drought
conditions range from one (Osmanabad) to 6 per cent (Beed). Only the area around Nanded
experienced acute drought conditions for one, per cent of the years,. Thus, the frequency of
occurrence of drought in Marathwada region ranges from once in four years around Parbhanl to
once in seven years in Osmanabad.
Madhya Maharashtra
The probability of occurrence of all categories of drought varies from 12 per cent (Kolhapur) to
32 per cent of the years (Rahuri, Ahmadnagar district) in the plains, while in the hilly region it
varies from 7 per cent (Chandgad, Kolhapur district) to 12 percent of the years (Gaganbavda,
Kolhapur district), Moderate drought conditions range from 11 per cent (Kopargaon and Shlrala)
to 26 per cent of the years (Rahurl) while severe drought conditions range from one (Bhusaval,
Nasik etc,) to 10 per cent of the years (Karjat, Karmala), Acute drought conditions in this region
were experienced only in areas around Pandharpur and Indapur for one per cent of the years.
Thus, in general, the frequency of occurrence of drought, except around Jalgaon, Kolhapur and
Shirala, ranges from once in eight years around Kolhapur to once in three years around Rahuri.
Vidarbha
The probability of occurrence of all categories of drought varies from 10 per cent (Hinganghat,
Wardha district) to 25 per cent of the years (Digras, Yavatmal dis- trict), Moderate drought
conditions ranges from 8 (Digras) to 23 per cent of the years (Arvi), while severe drought
conditions were experienced in most parts of Vidarbha region. However, around Shegaon it is 7
per cent of the years. Only around Shegaon acute drought conditions occurred for one per cent of
the years. Thus, the frequency of occurrence of drought in this region ranges from once in 10
years (Hinganghat) to once in four years (Digras).
Based on the probability of occurrence of rainfall, drought-prone areas located in Vidarbha,
Madhya Maharashtra, Marathwada and Konkan have been shown in the Plate -IV.
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Ground Water Surveys and Exploration
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The entire State has been covered by systematic hydrogeological survey by 1990-91. In the areas
where stage of ground water development is relatively high, reappraisal hydrogeological surveys
are being carried out since 1991-92. In the State programme of ground water exploration was
first started during 1956-58 in the Purna alluvial area of Amravati, Akola, Buldhana, Jalgaon &
Dhule districts. Intensive exploration was also carried out in the Sina-Man basin as a part of
special study. Since then regular ground water exploration is being carried out in the State under
normal exploratory programme. Upto March, 1991 in the State 388 exploratory wells, 180
observation wells, 27 piezometers and one slim hole have been drilled in various districts and
different formations.
Alluvial Area
Purna
In 7,400 sq.km. alluvial area of the Purna, exploratory drilling was carried out at 78 sites.
Exploration has revealed that Younger alluvium is about 70 m. thick while Older alluvium
extends from 70 to 450 m. depth. Further, an area of 2,300 sq.km. was delineated for further
ground water development through shallow tubewells upto 65 m. depth. In parts of the Purna
alluvium, quality of water is saline at all levels. The yield of tubewells varies from 0.5 to 20.0
Ips, while transmissibility (T) varies from 0.72 to 1,576 m2/day.
Tapi
It covers 5,200 sq.km. in Dhule and Jalgaon districts. Thickness of alluvium varies from 50 to
300 m. Exploratory drilling was carried out at 60 sites which reveals that the first potential
aquifer is within 100 m. bgl. while the second is below 250 m. bgl. The intervening zone
between 100 and 250 m. is generally clayey. It is further suggested that the scope of
development is mostly in deeper aquifers. The yield of tubewells varies from 0.5 to 31.5 Ips,
while 'T' varies from 7.2 to 3,162 m2/day.
Shallow Alluvial Area of Shivna (Aurangabad district)
It covers an area of about 150 sq.km. Exploratory drilling at 7 sites revealed that thickness of
alluvium is less than 30 m. and aquifer occurs between depth range of 15 and 26 m. bgl. The
yield of tubewells varies from 0.1 to 4.5 Ips.
Pravara -Godvari Alluvium (Ahmadnagar district)
It covers an area of 400 sq.km. Exploratory drilling at 7 sites reveals that thickness of alluvium
is less than 30 m. and aquifer zones between 19 and 26 m. bgl are suitable for ground water
development. The yield of tubewells varies from traces to 2.1 Ips.
Shallow Alluvium OF Brahmapuri Area (Chandrapur district)
Exploratory drilling carried out at 6 sites shows that thickness of alluvium is less than 23 m.
Permeable granular zones (aquifers) with thickness of 2 to 5 m. occur at a depth of 9 to 15 m.
bgl. The yield of tubewells varies from 0.13 to 3.0 Ips.
Gondwana Sediments (Semi-consolidated formation)
These semi-consolidated formations occur in an area of about 4800 sq.km. covering parts of
Gadchiroli, Yavatmal, Chandrapur and Nagpur districts.
(A) Gadchiroli District
It occupies an area of 960 sq.km in Sironcha Tahsil. Exploratory drilling at 9 sites upto a
maximum depth of 300 m have revealed that potential aquifers exist. between 30 and 100 m &
160 and 230 m. which can be developed. The yield of tubewells varies from 1.3 to 15 Ips, while
'T' varies from 15 to 87 m2/day.
(B) Yavatmal District
In an area of about 800 sq.km. 9 exploratory wells were drilled upto a depth range of 118 to 170
m. Permeable granular zones are encountered in Kamthi and Barakar formations beneath the
thick sequence of clay in Motur formation. Chemical quality of ground water in deeper aquifers
is doubtful.
(C) Chandrapur District
Around 2,920 sq.km. area was explored by drilling 58 boreholes to a depth varying from 35 to
300 m. The “T" of the Kamthi sandstone ranges from 18 to 500 m2/day and storativity (S) varies
from 3.6 x 10-2 to 9.4 x 10-4. It is also observed that hydraulic conductivity of Kamthi aquifer is
generally higher as compared with Barakar formations. The Kamthi aquifers yield upto 35 Ips.
The 'T' ranges from 300 to 500 m2/day.
(D) Nagpur District (Alluvium-covered Gondwana)
A well-field was constructed in Silewara coal field of Nagpur district which suggests that 'T'
varies from 85 to 250 m2/day and 'S' is 4.4 x 10-5.
Trap-Covered Gonwana
In Nagpur district, 14 exploratory wells were drilled in the orange belt to a depth range from 79
to 264 m. bgl and encountered Gondwana formation at a depth ranging from 10 to 137 m. bgl.
The yield of wells ranged from 0.78 to 16.4 Ips. which suggests that Gondwanas below the Trap
have a potential for ground water development.
Deccan Trap (Hard rock)
a) Sina-Man Basin: In an area of 5800 sq.km. (Ahmadnagar, Beed, Osmanabad, Solapur, Sangli
and Satara districts) exploratory drilling was carried out (1976-79) and 47 exploratory borewells
were drilled down to a depth ranging from 80 to 170 m. Based upon exploration broadly three
aquifers have been identified: (i) shallow aquifers (10 to 20 m.) (ii) semi-confined aquifers (20
to 40 m.) and (iii) confined aquifers beyond 40 m. The average 'T' of shallow aquifers varies
from 107 to 160 m2/day and of confined aquifers varies from 6 to 90 m2/day. The yield of
boreholes upto 8 Ips has been observed. It has suggested that around 95,500 shallow wells and
760 deep borewells can be constructed in this area.
b) Yesoda river basin: Exploratory drilling at 20 sites in the Yesoda basin reveals the three
aquifers upto a depth of 86 m. bgl i.e. (i) shallow aquifers (0-20 m., phreatic), (ii) semi-confined
aquifers (20-50 m.) and (iii) con- fined aquifers «50-70 m.). The 'T' of deep confined aquifers is
higher (10 to 60 m2/day) than the other two aquifers. It was suggested that shallow aquifers may
be developed through dug wells.
c) Wardha district: 27 borewells down to a depth of 103 to 201 m. were drilled which suggests
that the yield ranges from traces to 14.9 Ips. Higher yield was observed along or near
lineaments. At places, negative zones (dry vesicular zones) occur between depth range of 55 and
180 m. The 'T' varies from 10 to 90 m2/day.
d) Nagpur district: Exploratory drilling at 12 sites was taken up to a depth range of 85 to 201 m.
bgl. The yield of wells varies from traces to 38 Ips. It was observed that hydraulic parameters
and yield of wells is good in weathered and fractured basalts. The 'T' upto 250 m2/day has been
observed.
e) Ahmadnagar district: In the district, explorat6ry drilling was carried out at .29 sites to a
depth ranging from 55 to 202 m. and encountered red boles, inter-trappean clay beds which
poses difficulty during drilling. The yield of wells ranges from traces to 22 Ips. while 'T' varies
from less than 10 to over 30 m2/day. The yield of borewells is normally higher which have
proximity to lineaments and also in thick vesicular zones.
f) Satara district: Exploratory drilling was carried out at 18 sites to depth ranging from 69 to
301 m. and encountered red bole, inter-trappean clay posing difficulty in drilling. The yield
ranges from 0.6 to 15 Ips while 'T' varies from less than 10 to over 50 m2/day. Borewells
tapping vesicular zones and interflow zones are moderate yielding. Higher yields were observed
in wells located near lineaments in which 20 to 70 m. thick fractured zones were saturated.
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Ground Water Exploration in Purna Alluvial Area
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(Buldhana, Akola and Amravata Districts)
The Purna alluvial tract is an oval-shaped area tapering along the western margin covering about
7,400 sq.km. comprising parts of Amravati (3,460 sq.km.), Akola (2,560 sq.km.) and Buldhana
(1,390 sq.km.) districts. In this alluvial tract, ground water exploration was carried out in two
phases between 1956-58 and 1972-85. Exploration down to maximum depth of 426 m. at 78
sites has brought to light that thickness of alluvium is more than 426 m. in the northern part. The
entire thickness of alluvium can be broadly divided into two zones: Younger alluvium, upto a
depth of 70 m. and Older alluvium, beyond 70 m. The Younger alluvium is more sandy and at
places, sub- angular to sub-rounded, basaltic gravel has been encountered. In contrast to this,
Older alluvium is more clayey and, in general, sandy aquifer with gravel is encountered towards
its base.
Exploration has revealed that in the northern part of this alluvial tract ground water is generally
fresh and potable, while in the southern parts, covering an area of about 3,000 sq.km., ground
water is saline. An area of about 2,300 sq.km. as shown in the Plate -IX is delineated for future
ground water development through shallow tubewells of 65 m. depth. The yield of tubewells in
this zone is expected to be around 10 Ips for 30 m. of drawdown. Aquifer geometry along with
disposition of Older and Younger alluvium is shown in Fence diagram.
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Ground Water Exploration in Tapi Alluvial Area
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(Jalgaon and Dhule Districts)
Longitudinal tract of the Tapi alluvium covers an area of about 5,200 sq.km. comprising parts of
Dhule (2,560 sq.km.) and Jalgaon (2,680 sq.km.) districts. Its length is around 250 km. and
average width is around 25 km. Exploratory drilling was carried out at 36 sites to a maximum
depth of 300 m. which reveals that thickness of alluvium ranges from 50 to over 300 m. The
alluvium comprises clay, silt, sand, gravel, pebbles and occasionally boulders. The potential
sandy aquifers is generally restricted to 100 m. bgl, while between 100 and 250 m. bgl alluvium
is mainly clay. The second promising aquifer is encountered beyond depth of 250 m. Ground
water development through dug wells, dug-cum-bore wells, tubewells has reached its optimum
stage from the first aquifer. The discharge of exploratory wells ranges from less than one to 7.5
Ips. suggesting that alluvium of the Tapi is not very potential as com- pared to the Purna. The
quality of ground water at all levels is generally good and potable. Aquifer geometry and their
disposition is shown in Fence diagram.
Lineaments
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The lineament map of Maharashtra is prepared based on the landsat imagery on 1:1 million
scale. It is observed that in the State lineaments have NW-SE trend which is major, followed by
NE-SW. A few lineaments have N-S and E-W trend. The Azimuthal frequency diagram based
on number and direction of lineaments shows that in west coast (Mumbai-Ratnagiri) the major
trend is N-S followed by NE-SW. In Maharashtra plateau the general trend is NE-SW followed
by NW-SE. The general trend around Nagpur area is NW-SE followed by NE-SW. The density
of lineaments is higher in Mumbai, Ratnagiri, Nasik and Dhule districts.
In general, the lineament pattern in the State is guided by the trend of older formations. The
Aravalis have a NE-SW trend in Gujarat (just north of Dhule) and same is reflected as N-S
direction along the western coast and NW-SE and NNW -SSE in southern Maharashtra. The
older Dharwarian trend appears to change N-S and further eastwards as seen along the Satpura
belt. The Satpura trend (ENE-WSW) is reflected by the Deccan Trap in northern Maharashtra
and a little beyond. A similar effect is also seen between the northern Sahyadri ranges and the
Satmala-Ajanta ranges. The Satmala-Ajanta ranges are a likely continuation of the Satpura
(ENE-WSW) trend into Maharashtra.
Major Lineaments
The Tapi lineaments define the northern boundary of the Purna alluvium and cuts across the
Deccan Trap lava flows in the west. This lineament marks a pronounced fault that defines the
southern margin of the Satpura Horst. The Purna lineament displays a WNW-ESE trend along
the course of the Purna river. It joins the lineaments to the east of Jalgaon.
The Godavari lineament with NW-SE trend extends over the Deccan Trap terrain. The Kadam
lineament has given rise to northerly dips in Deccan Traps in Yavatmal district. The Upper
Godavari lineament extends in WNW-ESE direction from west of Nasik to near Parbhani in the
east. This lineament cuts across the lava flows and is characterised by the Quaternary tectonic
movements. The Ghod lineament is a set of fracture in lava flows. The Varna lineament trends in
a NW-SE direction and is considered as a fault affecting the Deccan Traps.
The Sahyadri lineaments are restricted to north-south coastal plains and the Sahyadri range.
These lineaments represent fractures in lava flow. The Chiplun linea- ment extends in a NNWSSE directions.
Further, the NW-SE and NE-SW weak zones are well reflected in the overall drainage pattern
and as well as ridge line separating the basin. Thus the dominant NW- SE weak zones are
aligned by all major rivers.
Thermal springs are generally associated with lineaments. The concentration of thermal springs
are more along the major lineaments in the Western Coast and the Satpura range (northern
Maharashtra).
The yield of dugwells and borewells is generally high if these are located along the lineaments.
It is observed that around 80 per cent of high yielding borewells are associated with lineaments.
Still higher yield is observed at the intersection of two lineaments. Yield upto 50 Ips. is recorded
in the borewells tapping fractured zone associated with lineaments.
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Hydrogeology
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Hydrogeology of the State is exhibited through hydrogeological formations, their lithology,
aquifer types and their yield characteristics. Apart from this, area with high salinity of ground
water is also shown. Lithology of various water-bearing formations have been shown with
symbols while aquifer types have been divided into three i.e. granular, granular and fissured and
fissured. The yield characteristics of various aquifer types have been shown with shades of
different colours.
In a major part of the State, basalts with or without intertrappean sediments form the waterbearing formation. Quaternary sediments comprise sand, silt, clay, calcareous concretions and
are mainly confined to Tapi and Purna basins and form extensive granular aquifers. The yield of
wells in these formations is generally above 50 m3/hr. Laterites of Quaternary Age occur at
places mainly in Sindhudurg district which are discontinuous and yield of wells varies from 10
to 50 m3/hr. Granular-and- fissured formations as an aquifer comprises basalts, sandstones,
(Mesozoic to Ceno- zoic) grit, shale, conglomerate, limestone (Mesozoic/Upper Palaeozoic). In
these water-bearing formations, the aquifers are generally discontinuous. The yield of wells in
basalt varies from 2 to 20 m3/hr. while in the rest of the formations under this group ranges from
10 to 50 m3/hr. Fissured aquifer type consists of Pre-Cambrian (Vindhyan) sediments
comprising sandstones, quartzites, shale, limestone, partly cavernous etc. Pre-Cambrian
formation comprises gneisses, granites, shales, phyllites etc. which also are grouped under this
aquifer type. The fissured type of aquifers are mainly discontinuous and yield of wells ranges
from 2 to 20 m3/hr.
In parts of the Purna alluvium, ground water is highly saline. Water-logged area is mainly
confined to the Nira Canal Command. Along the Western Ghats, there are numerous hot springs
in which, temperature of water, is as high as 69°C.
The Deccan Trap, which forms a major water-bearing formation in the State, has definite
characteristics which consists of a sequence of lava flows and each lava flow can be divided into
lower massive and upper vesicular units. In the massive unit, ground water occurs in joints,
fractures, faults and similar other zones of weakness. In the vesicular unit, which has primary
porosity and permeability, ground water occurs in intra-granular porous space. In other
consolidated formations, comprising Vindhyan sedimentaries and Pre-Cambrian metasediments, ground water mainly occurs in the weathered mantle and also along joints, fractures
and foliation planes. The semi consolidated formations which forms granular/and/fissured
aquifers of Upper Palaeozoic to Cenozoic sedimentaries, ground water occurs in inter-granular
pore space and also in secondary openings such as fractures, joints, etc. In unconsolidated
granular formations which mainly comprise alluvium, ground water occurs in inter-granular pore
spaces and by far the best aquifers in the State. The thickness of alluvium in Tapi and Purna
basins varies from 100 to more than 450 m.
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Electrical Conductivity of Ground Water
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The quality of ground water is controlled by mineralogical composition of the Formation,
climate, depth to water level, etc. Electrical Conductivity (EC) of water is indicative of total salt
content of water. It also decides suitability of its uses for parts of irrigation, human and cattle
consumption. Based on the water samples collected form the hydrograph network stations during
the year 1990, a map showing EC of ground water has been prepared. In general, quality of
ground water in the State is within permissible limit and water can be used for domestic and
irrigation purposes. Higher EC (more than 2,000 micro mhos/ part of the m. at 25°C) of ground
water was observed in parts of Amravati, Akola, Aurangabad, Jalna, Pune, Satara, Sangli and
Nagpur districts. In major part of the State EC of ground water is between 750 and 2,000 micro
mhos/ cm. at 25°C. In the Konkan and parts of Nasik, Dhule, Ahmadnagar, Aurangabad,
Nanded, Parbhani, Jalgaon, Beed, Osmanabad, Latur, Nagpur, Bhandara, and Gadchiroli
districts the EC of ground water was less than 750 micro mhos/cm. at 25°C. Eight isolated
pockets having EC of ground water more than 3,000 micro mhos/cm. are observed in
Chandrapur, Amravati, Akola, Buldhana, Aurangabad, Ahmadnagar, Sangli and Solapur
districts. Incidentally, most of these areas also falls in surface water irrigation projects. In major
part of the Purna alluvium ground water is saline in shallow and deeper aquifers.
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Quality of Ground Water
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The quality of ground water is indicative of the nature of water-bearing formation and at times it
differentiates between recharge and discharge areas. Since rainfall is the main source of recharge
to ground water, mostly water which is recharged to ground water will be of bicarbonate type.
However, during the passage through aquifers, the water becomes mineralised as it travels from
recharge to discharge areas. In the State, principally, five types of water are observed based upon
the analysis of water samples of hydrograph network stations and the same have been shown in
the Plate -XIX. These types are:
1. Calcium bicarbonate type
2. Magnesium bicarbonate type
3. Sodium bicarbonate/Sodium chloride type
4. Magnesium chloride type
5. Calcium chloride type
Calcium bicarbonate type
This type of water mainly occurs in the Coastal Tract of Maharashtra and also on either side of
the Western Ghats. Apart from this, it occurs in other parts of the districts except in central part
which is under canal command and covers around 20 per cent of the State.
Magnesium bicarbonate type
This type of water occurs throughout the State leaving parts of the Coastal Tract covering around
40 per cent of the area of the State. Generally, EC is less and such water generally occurs in the
recharge areas.
Sodium bicarbonate/Sodium chloride type
This type of water occurs in around 27 per cent of the State's area. In the entire alluvial patch of
the Tapi and the Purna alluvium, this type of water is very common.
Magnesium chloride type
This type covers an area of around 8 per cent of the State. In the process of ground water
movement, bicarbonate type of water normally changes to chloride type depending upon the
composition of water-bearing formation. This type of water is found in isolated patches
throughout Maharashtra except in Coastal tract.
Calcium chloride type
These waters are generally characterised by higher EC values and chloride con- tent of more
than 50 per cent and are generally found in lower reaches of the basin/ watershed. These are
found in three isolated pockets of the State.
In general, in the entire State, ground water is mainly of bicarbonate type. This may be because
of the fact that more than 90 per cent of the State is underlain by hard rocks and movement of
ground water is relatively fast.
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