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