| |
|
West
Bengal |
 |
|
| |
|
Head |
Description |
| Geographical
Area (sq. km.) |
87,853 |
| Population |
8,02,21,171 |
| Rural
Population |
5,77,34,690 |
| Urban
Population |
2,24,86,481 |
| No.
Of Districts |
19 |
| No.
Of Blocks |
340 |
| Normal
Annual Rainfall(mm) |
1,234
- 4,136 |
| Net
sown area ( in Thousand hectare) |
5,465 |
| Area
under forest( in Thousand hectare) |
1,192 |
| Area
not available for cultivation (in
hectares) |
16,50,833 |
| Other
uncultivated land excluding fallow |
1,60,271 |
| Fallow
land ( in Thousand hectare) |
219 |
| Cropping
intensity( %) |
167 |
| Dynamic
Resource ( 91) in MhaM |
2 |
| Available
dynamic resource for irrigation
( 91) in MhaM |
2 |
| Net
annual ground water draft ( 91)
in MhaM |
.48 |
| Stage
of ground water development ( 91) |
24% |
| Number
of dark blocks |
1 |
| Number
of Grey blocks |
19 |
| Utilisable
irrigation potential (91) from GW
in Mha |
3 |
| Irrigation
potential created ( 91) in Mha |
2 |
|
 |
| |
Physiography
& Landforms
:
The State of West Bengal can be
divided into four physiographic divisions:
|
Districts of Darjeeling, Jalpaiguri
and Koochbihar in the Himalayan Region. |
|
District of Purulia
and Western part of the districts of Barddhaman,
Medinipur, Birbhum and northern part of
Bankura occupy the eastern fringe of Chotanagpur
Plateau. |
|
Sundarban area of the South 24 Parganas
and small part of North 24 Parganas form the
deltaic zone. |
|
Remaining areas of the State being plains. |
Drainage
:
The State of West Bengal falls under
3 major River Basins:
|
The Brahmaputra Basin - Part
of Darjeeling, Jalpaiguri and Koochbihar districts. |
|
The Ganga Basin - Part of Darjeeling, Jalpaiguri
and all the remaining districts. |
|
The Subarnarekha Basin - Parts of Purulia,
E&W Medinipur district. |
Rainfall :
The average rainfall in the State
is 1750 mm. In the Himalayan Region i.e in northern
part the average rainfall ranges from 2500 - 6000
mm. In the southern part average rainfall ranges
from 1125 - 1900 mm.
Soil
:
The soil pattern in the state
|
Agro
climatic Zone ( Districtwise) |
Soil
type |
| Entire North Bengal
( Darjeeling, Jalpaiguri & Cooch Behar) |
Acidic |
| Gangetic alluvium (
N&S Dinajpur, Murshidabad, Nadia, Hugli,
Haora, Birbhum , N & S 24 Parganas) |
Alluvial |
| Vindhyan family soil
( Barddhaman, Murshidabad, Medinipur (W),
Haora, Birbhum & West Dinajpur) |
Alluvial |
| Lateritic Red Soil(
Birbhum, Barddhaman, Medinipur, Bankura,
Puruliya, Malda, North & South Dinajpur)
|
Alluvial |
| Coastal Soil (South
24 Parganas, North 24 Parganas and East
Medinipur) |
Coastal Saline |
Hydrogeology
:
Based on the geological and geomorphological
set up, characteristics of the aquifers and chemical
character of ground water the State can be divided
into two broad units.
| |
Fissured
Formations: Ground water occurs
in these formations in the upper weathered
mantle(thickness5-10m) and at deeper levels(60-100m
depth) in the fractures, fissures and joints
where limited quantities of ground water
(less than 20m3/hr) may be available from
borewells and large dia dugwells. |
| |
Porous Formations: Ground water
occurs in this formation both under water
table and confined condition. In Nadia,
Murshidabad(except Kandi Sub-division) districts
down to 150m there is absence of any significant
clay beds making the entire aquifer upto
150m depth to occur under water table condition.
In the Bhabar Zone(foothills of Himalayan
trench) aquifers are having very deep water
table and are characterised by high seasonal
variation of water table to the tune of
10-12m. in this lateritic part occurring
in parts of Birbhum, barddhaman, Bankura
& Medinipur districts, individual aquifers
being of limited thickness and discontinuous
nature. The potentiality of this aquifer
is very poor. By and large yield of the
tube well(down to 100-400mbgl) varies from
80-100m3/hr.
Based on the yield prospects the State can
be devided into three parts namely:
| |
Areas of prolific
ground water resources (yield is
more than 150m3//hr) : Jalpaiguri,
Coochbihar, Medinipur,N&S 24-
Parganas districts |
| |
Areas with
moderate yield(yield between 50
- 150m3hr) : Comprising part of
Malda,Uttar & Dakshin Dinajpur,
western part of Murshidabad,marginal
tract of Birbhum, Barddhaman, Bankura
and Medinipur districts. |
| |
Areas
with limited yield prospect (yield
less than 503hr) : Extreme marginal
tracts of Medinipur, Bankura, Purulia |
|
In the coastal tract
ofEast Medinipur, S 24- Parganas, southern part
of N 24- Parganas, Bidhannagar and some parts
of Haora lying in the active delta of the Ganga
--- the Bhagirathi river system ground water occurs
under a characteristic hydrochemical situation
in which fresh water group of aquifers occurs
within span of 120-300m sandwitched between saline
to brackish aquifers. Yield of the tube well varies
from 100-150m3//hr. Some of the hot springs (35-410C)
from deep seated fractured zones of older rocks
occurs around Bakreswar, Birbhum districts.
Activities of Central Ground Water Board, ERO,
Kolkata
:
|
Based
on non Conventional and Conventional Technique,
presence of high yielding fresh water bearing
zones (aquifer) have been identified in
hard rock, alluvial area and coastal area
of West Bengal. |
| |
Exploratory
well cum production well yielding fresh
& potable ground water have been constructed
in hard rock, Laterite, Alluvial plain,
bouldary formation, arsenic infested and
coastal area. Till March 2003 282 EW have
been drilled. |
|
Short Term Investigations
have been carried out and technical reports
have been issued for implementation. |
|
Arranging
regular Mass Awareness Programme & Training
Programme in different parts of West Bengal,
for dissemination of information & knowledge
related to ground water conservation, development
and Artificial Recharge of ground water. |
Findings of Central Ground Water
Board in the State of West Bengal:
|
Formation |
District |
Findings |
Remarks/
Recommendations |
| Consolidated/
Semiconsolidated/Hard Crystalline rocks |
Purulia,
Bankura,
Medinipur,
Barddhaman,
Birbhum
|
Ground
water occurs in :
i) Weathered residuum within 10mbgl.
ii) Fractures within 65mbgl having discharge
within 20 m3/hr.
|
In this water scarce area, topographic lows, zone of intersection
of regionally extended joints & fractures
(to be identified by resistivity survey)
are the suitable locales for ground water
development through dug and dug-cum-bore
wells. |
Gondwana
Sandstone
|
Purulia,
Barddhaman,
Birbhum
|
Ground
water occurs in the fractured zone within
100mbgl generally discharging 10 m3/hr
with maximum discharge of 22m3/hr.
|
Borewells
within 100m depth is found suitable. Location
of the well site should be pinpointed
after detailed geophysical survey. |
| Unconsolidated
/Recent Alluvium
|
Darjeeling,
Jalpaiguri,
Kochbihar,
Uttar Dinajpur,
Dakshin Dinajpur,
Malda,
Murshidabad,
Nadia,
North 24 Parganas,
Hugli,
Haora,
Medinipur,
Barddhaman,
Bankura,
Birbhum
Coastal areas/
North 24 Parganas, South 24 Parganas,
Medinipur, Haora
|
Ground
water occurs both under unconfined &
confined condition within the explored
depth of maximum 600mbgl. Aquifers are
fairly thick & regionally extensive
with large yield prospect of about 150m3/hr.
In Birbhum and Bankura districts aquifers
beyond 136mbgl upto the drilled depth
of 350mbgl in the Tertiary formation are
found under autoflow condition.
The occurrence of Arsenic in ground water
in the depth span of 20-80 mbgl restricted
mainly in the eastern part of Bhagirathi
river has posed a serious problem. In
view of the situation exploration work
has been undertaken in the arsenic infested
areas & arsenic free deeper aquifers
could be identified beneath a thick clay
bed in Nadia district.
Fresh ground water bearing
aquifer occurring in varying depth ranges
within 180-360mbglwithin the drilled depth
of 600mbgl have been established. The
fresh group of aquifers are sandwiched
between saline/brackish aquifer. The top
saline/brackish aquifer lies within the
depth span of 20-180m with maximum depth
of 320mbgl in the extreme south. Suitably
constructed tubewell tapping 35m cumulative
thickness can yield 100-150m3/hr. Shallow
fresh water aquifers occur in present
day dunes in Digha-Ramnagar area of Medinipur
dist. down to the depth of 9 mbgl &
in levee deposit within 50mbgl in Baruipur
-Sonarpur-Bhangar-Caning tract in South
24 Parganas. High Concentration of As
in ground water is reported in this levee
deposit. |
Ground water can be utilised through heavy-duty tubewells
within 120mbgl & shallow tubewells
within 60mbgl. In arsenic infested area
development of shallow aquifers should
be avoided. |
| Older Alluvium |
Bhabar
zone/ parts of Darjeeling & Jalpaiguri
Barind Tract/ parts of Malda,Dakshin Dinajpur
Lateritic Terrain/ parts of Birbhum, Barddhaman,
Bankura, Medinipur, Murshidabad
|
In
the submontane zone of Himalaya the sediments
consist of unassorted materials varying
from boulders to sand of various grades.
The aquifers are having deep water table
& are characterised by high seasonal
variations of water level to the tune
of 10-12m. Recent exploration identified
the potential granular zones within the
depth range of 150mbgl capable of yielding
upto 68m3/hr.
Ground water under semiconfined to confined
condition below a blanket of about 60m
thick clay bed. Saturated granular zone
of discontinuous nature generally occurs
in the depth span of 65-110m, which is
capable of yielding upto 50m3/hr.
The maximum thickness of older alluvium
is within 50m, which is capped by laterites.
Individual aquifer in older alluvium is
of limited thickness and discontinuous
in nature has poor yield prospect. Recent
exploration in the tract has indicated
the presence of unconsolidated to semi
consolidated Tertiary gravel & sand
stone, porous in nature, within depth
zone of 100-140mbgl.which has the yield
prospect of 180m3/hr.
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