Book Synopsis: Groundwater Hydrology and Groundwater
Quality in and around Bangalore city by Department of Mines and Geology, 2011
Bangalore city is plagued with various water
problems. And with the continuous demographic growth the groundwater exploitation
has reached its limit largely through borewell extraction. However, little has
been known about the actual picture of groundwater levels, hydrogeology and
quality of this groundwater. Therefore, this study was conducted to assess the
current situation on both these parameters in Bangalore bu Department of Mines
and Geology.
The study is an analysis of over 3000
groundwater samples collected over an area of 800 sq. km. in and around
Bangalore city. The study focused on urban groundwater hydrology,
groundwater quality and quality of Lake Water.
1.
Urban groundwater hydrology:
Assessing groundwater levels becomes essential
when water is the biggest concern. But, many of the wells including those set
up by the department to monitor groundwater level fluctuation dried up. In the
span of one year (February 2009-January 2010) 14, 483 borewells were drilled.
|
Months
|
New borewells added each month
|
Borewells registered with BWSSB
|
Monthly % growth
|
|
Jan 09
|
|
91018
|
|
|
Feb 09
|
924
|
91942
|
1.02
|
|
Mar 09
|
705
|
92647
|
0.77
|
|
Apr 09
|
965
|
93612
|
1.04
|
|
May 09
|
1136
|
94748
|
1.21
|
|
June 09
|
748
|
95496
|
0.79
|
|
Jul 09
|
904
|
96400
|
0.95
|
|
Aug 09
|
868
|
97268
|
0.90
|
|
Sep 09
|
2062
|
99330
|
2.12
|
|
Oct 09
|
838
|
100168
|
0.84
|
|
Nov 09
|
875
|
101043
|
0.87
|
|
Dec 09
|
2699
|
103742
|
2.67
|
|
Jan 10
|
1759
|
105501
|
1.70
|
|
Total
|
14483
|
Average
|
14.88
|
Hence, need was felt to increase the wells. Based on
geo-hydrological features of the area, 18 sites were identified for
construction of Piezometers in BBMP area. However, due to field
constraints only 12 sites were confirmed.
In addition to the collection of samples from borewells, the study
also collected other important details like depth of borewell, casing depth,
yield of borewell, etc. It was observed that deeper borewells are more in the
South East, South west and Northern parts of BBMP area.
2.
Evaluation of groundwater quality
As mentioned above, approximately 3000 samples were collected and
analyzed by Chief Chemist in the Directorate of Mines and Geology.
I.
Total Dissolved Solids (TDS):
Research suggests that deeper borewells have comparatively higher
levels of TDS because longer the groundwater moves through the rocks or
sediments the more mineralized it becomes.
TDS values of >1000 mg/L:- SE zone accounts for 33% followed by
NE zone and NW zone with 27.5% and 25.54% respectively.
II.
Fluoride:
Concentration of fluoride in groundwater depends on the
geological, chemical and physical characteristics of aquifers. Fluoride
concentration of less than 1.0 mg/L in drinking water effectively reduces
dental caries without harmful effects on health. In Bangalore, highest
fluoride content of 5.54 mg/L was observed near Bellandur.
Below table details out the fluoride in groundwater
(>permissible limit) of 1.5 mg/L
|
Sr. no.
|
Location
|
Content (mg/L)
|
|
1.
|
Green Glen layout
|
4.2
|
|
2.
|
Bellandur
|
2.3
|
|
3.
|
Bellandur
|
3.0
|
|
4.
|
Bellandur
|
3.3
|
|
5.
|
Bellandur
|
1.7
|
|
6.
|
Bellandur
|
5.5
|
|
7.
|
Bellandur
|
3.6
|
|
8.
|
Green glen layout
|
4.8
|
|
9.
|
Green glen Layout
|
5.0
|
|
10.
|
Bellandur
|
2.4
|
|
|
|
|
III.
Location of high content (above permissible limit of Fe, No3,
TH) in Groundwater, Bangalore city
The high content of Iron in the groundwater samples is
attributable to the corrosion of casing pipes of the borewells. The iron
content >1.0 mg/L is undesirable for drinking purposes.
Nitrate content in the groundwater may be due to presence of
sewage in the channels. High nitrate content is harmful especially for infants
and even can cause carcinogenesis. The undesirable drinking water range is
>45 mg/L.
Hardness of water is mainly due to dissolved calcium and magnesium
salts. The undesirable drinking water limit is > 600 mg/L. Out of the total
2210 samples tested for hardness, 45% were within desirable limit and only 9%
were beyond permissible limit.
|
Fe >1.0 (mg/L)
|
No3 >45 mg/L
|
TH >600 mg/L
|
|
Harlur
|
Munnakolalu, Marathahalli
|
Doddanakundi
|
|
Kasavanahalli
|
Varthur
|
Kundalahalli
|
|
Kormangala
|
Junnasandra
|
Panathuru
|
|
Kudlu main road
|
Kaikondrahalli
|
Parappana Agrahara
|
|
Kundalahalli gate
|
Kasavanahalli
|
Singasandra
|
|
Mahadevpura
|
Chikka Bellandur
|
Bellandur
|
|
Marathahalli
|
Doddakanneli Dinne
|
Devarabisanahalli
|
|
Munnekolalu
Panathuru Dinne
|
Kudlu Village
|
Ibblur
|
|
Sarjapur road
|
Kundalahalli
|
Yamlur
|
|
Yamlur
|
Parappana Agrahara
|
|
|
Varthur
|
Marathahalli
|
|
|
|
Mahadevpura
|
|
|
|
Singasandra
|
|
|
|
Singasandra Industrial area
|
|
IV.
Location of Heavy metals
Of the total 275 samples collected and were tested for heavy
metals like Zinc, Lead, Copper, Manganese, Aluminium, Chromium, Chloride,
|
Location
|
Zn
|
PB
|
CU
|
Mn
|
Al
|
Cr
|
TH
|
Cl
|
|
Sarjapur road, Agara post
|
0.44
|
0.00
|
0.11
|
0.39
|
0.00
|
0.00
|
0.00
|
0.00
|
|
Kaikondrahalli,
|
1.12
|
0.02
|
0.02
|
0.72
|
0.00
|
0.00
|
0.00
|
0.00
|
|
Singasandra Main Road
|
0.09
|
0.00
|
0.00
|
4.00
|
0.00
|
0.00
|
0.00
|
0.00
|
|
Dhariwal Ind. Ltd., Singasandra
|
0.18
|
0.00
|
0.00
|
0.34
|
0.00
|
0.00
|
0.00
|
0.00
|
|
AES layout, Singasandra
|
0.06
|
0.00
|
0.00
|
0.33
|
0.00
|
0.00
|
0.00
|
0.00
|
3.
Chemical analysis results of lake water samples,
Bangalore city
The study also concentrated on lakes in
Bangalore. Totally 161 samples from 96 lakes of BBMP area were collected. Below
is the snapshot of couple of lakes in the sarjapur watershed:
|
Name
|
Area
(ha)
|
Sample
location
|
Cl
|
PO4P
|
TSS
|
DO
|
COD
|
NO3
|
TH
|
F
|
pH
|
Zn
|
PB
|
Cu
|
Mn
|
Al
|
Cr
|
EC
MPN/100 ml
|
TC
MPN/100 ml
|
|
Bellandur
Tank
|
307.35
|
Outlet
|
132
|
0.1
|
150
|
Nil
|
57.6
|
7.48
|
220
|
0.38
|
7.87
|
0.13
|
Nil
|
Nil
|
0.22
|
|
|
|
|
|
|
|
Middle
|
134
|
0.1
|
192
|
|
76.8
|
7.91
|
244
|
0.37
|
7.8
|
0.12
|
Nil
|
Nil
|
0.22
|
|
|
|
|
|
|
|
Inlet
|
109
|
5.05
|
498
|
Nil
|
96
|
9.73
|
208
|
0.4
|
7.51
|
0.19
|
Nil
|
Nil
|
0.23
|
|
|
|
|
|
|
|
Inlet 2
|
148
|
5.11
|
363
|
|
134.4
|
11.165
|
240
|
0.36
|
7.63
|
0.44
|
11
|
0.07
|
0.28
|
|
|
|
|
|
Devarabisanahalli
|
4.64
|
Inlet
|
442
|
5.21
|
145.5
|
3.6
|
|
4.51
|
316
|
0.44
|
8.51
|
0.2
|
Nil
|
0.04
|
0.09
|
|
|
>1600
|
>1600
|
|
|
|
Middle
|
291
|
5.16
|
191
|
|
|
12.08
|
368
|
0.45
|
8.11
|
0.12
|
Nil
|
0.03
|
0.07
|
|
|
|
|
|
Haralur
|
9.58
|
Inlet
|
269
|
0.01
|
107
|
4.6
|
38.4
|
3.09
|
196
|
0.59
|
8.25
|
0.08
|
Nil
|
Nil
|
0.11
|
|
|
|
|
|
Kasavanahalli
|
15.83
|
Inlet
|
230
|
0.01
|
175.5
|
8.2
|
57.6
|
3.48
|
196
|
0.51
|
8.51
|
0.08
|
Nil
|
Nil
|
0.17
|
|
|
|
|
|
Kudlu
Dodda Kere
|
19.79
|
Inlet
|
297
|
2.01
|
99
|
|
38.4
|
2.35
|
248
|
0.43
|
8.87
|
0.14
|
Nil
|
Nil
|
0.22
|
|
|
|
|
|
|
|
Outlet
|
288
|
2.5
|
6723
|
7.6
|
480
|
5.41
|
284
|
0.45
|
9.27
|
0.09
|
Nil
|
Nil
|
0.07
|
|
|
|
|
|
Kodagi
Singasandra
|
4.21
|
Inlet
|
274
|
0.01
|
29
|
12.2
|
37.76
|
6.796
|
192
|
0.92
|
9.14
|
1.08
|
Nil
|
Nil
|
0.09
|
|
|
|
|
