Thursday, July 31, 2014

Book Synopsis: Groundwater Hydrology and Groundwater Quality in and around Bangalore city by Department of Mines and Geology, 2011

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