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Session6: Groundwater and Hydrogeology

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Chairman: Dr. Ranganna G.

Rapporteur: Saira K. Varghese

Groundwater Recharge in an Urbanising Area: A Case Study for Bangalore Urban and Rural Districts, Karnataka State, India

Nataraju C., Shivakumar J. Nyamathi and Ranganna C


Water is the vital element of life and truthful companion of humanity. It is the most abundant element on the earth, covering about 1400 million cubic kilometers, of which only 0.03% is usable – the rest forming part of oceans and polar ice-caps. Urban domestic and industrial consumers are using larger amounts of water and consequently depleting the available resources. The goal should be to promote water use and management in such a way that society’s needs are met while at the same time, water resources are protected. Non availability of adequate drinking water due to progressively depleting surface and groundwater is a big challenge to the water management system.

 Even today, more than 90% of our rural population is primarily dependent upon groundwater. Water supplies from groundwater sources are becoming increasingly important, but they are threatened by unplanned exploitation and by contamination from many sources. Protection and conservation of groundwater is therefore a top priority task, particularly in such regions of limited available water resources.

 Groundwater is derived from precipitation on the earth’s surface that gradually percolates to the sub-soil through the porous strata or openings through rock formations. The process of infiltration of water and subsequent water movement is an exceedingly complex process. The aquifer complex transports the groundwater from areas of replenishment to areas of need.

 Groundwater recharge, in a general sense, is the downward flow of water reaching the water table, forming an addition to the groundwater reservoir. Recharge of groundwater may occur naturally from precipitation, rivers, canals and lakes and as man-induced phenomena via such activities as irrigation and urbanisation. Quantification of the current rate of natural groundwater recharge is thus a basic prerequisite for efficient groundwater resource management and is particularly vital in arid and semi-arid where such resources are key to economic development.

 Urbanization has profound impacts on the hydrological cycle, effecting changes in groundwater recharge mechanisms. The provision of water supply, sanitation and drainage are the key elements of  the urbanisation process. A common factor to most urbanisation is that it results in –

(i)                   Impermeabilisation of a significant proportion of land surface, and

(ii)                 Major water imports from outside the urban limits.

 Urbanisation also causes major changes in the frequency and volume of recharge, although these changes cannot be measured directly and are thus difficult to quantify. Some urbanisation processes also cause radical changes in the quality of the recharge. The changes in recharge caused by urbanisation in turn influence the groundwater levels and flow regimes in the underlying aquifers.

 A field investigation has been carried out for three successive water years over Bangalore (rural and urban) district for recharge assessment.  The district covers an area of 8039 and falls in between north latitude 12°15˘ - 13° 31˘ and east longitude 77° 4˘ and 77° 59˘. The population in the district is 9.7 million according to 2001 census. The district receives annually about 879mm of rainfall.

 The central groundwater board (CGWB) has issued guidelines (1997) to assess the groundwater resource adopting two methods viz.,

i.                     based on water table fluctuation data

ii.                    rainfall infiltration data

 Here in our study in Bangalore, water table fluctuation method has been adopted. Data on geomorphology, geology, soils, land use, rainfall, infiltration, water table, fluctuations, specific yield, evaporation losses, utilisable losses, other inputs have been considered during the study.

 Also, monsoon and non-monsoon seasonal recharge values are quantified for 59 rain gauge stations. The probable percentage of rainfall contributing to groundwater recharge for the area receiving less than 700 mm annual rainfall, has been assessed to vary from 3 to 5. The steps and methodology followed and data utilised for assessing quantum of rainfall recharged into the aquifers are presented in the paper.

Department of Civil Engineering, 
S.J. College of Engineering, Mysore. Karnataka. India
Department of Civil Engineering, 
Bangalore University, Jnanabharathi Campus, 
Bangalore. Karnataka. India
UGC-DSA Centre, Department of Mathematics, 
Bangalore University, Central College Campus, 
Bangalore. Karnataka. India
Phone: 2220483 E-mail: