CS(AR)-13/99-2000 : Artificial recharging of an unconfined aquifer with an injecting well (Karnataka)

Abstract

The increased dependence and utilisation of groundwater has caused depletion of aquifers in many parts of our country. Artificial recharge methods using percolation tanks, injection wells, spreading basins etc. have been proposed and implemented to certain extent in order to resuscitate the depleting groundwater resources. The important issues associated with artificial recharge are the nature of the rechargeable water source, the system of recharge to be used, the expected injection rates, the hydraulic response of the system to injection and the management of the injected water as part of the total water resources system. Mathematical modelling is a powerful tool in the investigation of artificial recharge processes and evaluation of viable strategies.

Most of the river basins of peninsular India, have been facing groundwater development problems varying in nature and severity. Being no exception, Ghataprabha sub-basin of Krishna river basin too has its own problems. It has got a wide spectrum of issues such as cases of failure of wells at several places on the one hand, while some areas becoming unfertile due to waterlogging. Hukkeri taluk in the Ghataprabha sub-basin has been experiencing depletion its aquifers for a number of years. The problem has been investigated through mathematical modelling techniques and plausible measures for recharging the aquifers have been evolved.

In order to address local-scale groundwater issues a calibrated three dimensional regional finite difference model, based upon the USGS modular three dimensional finite difference ground water flow model MODFLOW, generated for the Ghataprabha sub-basin has been used as a basis for the local-scale modelling of the Hukkeri region, which has been experiencing drying of open and bore-wells in recent times. The generated microscopic model with finer mesh is calibrated and validated using the existing USGS code MODFLOW. Various options of artificial recharge measures have been tried out with the calibrated model and results analysed. Analysis of the results shows that maintaining a higher water-level in the Ghataprabha river reach in downstream of Hidkal Dam and in Hiranyakeshi tributary is the best option for maintaining a reasonable water table depth in the area.