Groundwater Quality Modeling of Amaravathi River Basin of Karur District, Tamil Nadu,Using Visual Modflow

Amaravathi river basin at the down stream of Karur Town is severely polluted due to discharge of partially treated effluent by the textile bleaching and dyeing units. There are 487 units and they treat the effluent either in individual effluent treatment plant (IETP) or common effluent treatment plant (CETP). Daily about 14600m3of coloured effluent with total dissolved solids (TDS) in the range of 5,000 10,000 mg/l is let into river Amaravathi. A study has been conducted using Visual MODFLOW 2.8.1 version. The study area is limited to 320 sq.km. This 320 sq.km is divided into 4572 cells with grid size of 350m × 200m with two layers. The groundwater monitoring data, lithology, hydro geological parameters, topography, rain fall data obtained from PWD, CGWB, Survey of India, India Metrological Department are used in the model. The MODFLOW and MT3D models are calibrated and validated. The validated model is used for simulation of the ground water quality for next 15 years under five difference scenarios:(i) if the present system with 10,000 mg/L TDS discharge into river continues, (ii) if the CETPs meet the TDS discharge standards of 2100 mg/L and discharge the effluent into river, (iii) if the quantum of discharge is doubled with TDS level of 2100 mg/L, (iv) if the dyeing units go for reverse osmosis plant and recycle the entire effluent and achieve zero discharge, (v) 1.5 time ground water recharge and zero discharge by the units. The simulation results show there is no improvement in ground water quality even the effluent meet the discharge standards for the next ten years. When the units go for zero discharge then there will be an improvement in the quality of ground water over aperiod of few years.