In association with six-other CSIR institutes, NGRI (the nodal agency) is working for development of techniques and methodologies for exploration, assessment and management of ground water in hard rock areas in coordination with the Indian Toxicological Research Centre, Lucknow, National Environmental Engineering Research Institute, Regional Research Laboratory, Bhopal, Central Salt, Marine Chemical Research Institute, Bhavnagar, National Physical Laboratory, Delhi besides Central Ground Water Board.
NGRI has been carrying out extensive research in ground water exploration and has developed data and useful techniques through geophysics, geohydrology, isotope hydrology to tackle the problems of ground water in an efficient way, Dr VP Dimri, director, NGRI told FE.
As a pilot project, the institute is working to estimate and reduce the fluoride content in Velapally village in Nalgonda district of Andhra Pradesh. This village is famous for high fluoride content in the ground water leading to flurosis (a disease which causes retardation of growth) and lung cancer.
We have analysed about 250 samples of soil which contained about 100-800 ppm in the soil and the water contained about 7 ppm of fluoride as against the normalcy of 0.5-1.5 ppm. Similar projects are in the plan for villages near Ujjain and Ghatia in Madhya Pradesh, said Dr Pradip K Govil, deputy director of NGRI.
To address the problem of increased level of certain chemical species, fluoride, thorium and other toxic elements in the ground water, a detailed soil chemistry is initially analysed with an indepth study of the chemical constituents, Dr Govil, also the project coordinator, said.
We are planning for artificial recharge by using rain water and diluting the fluoride content in existing water. Added to this, we have proposed for construction of check level dams besides defluorination plant in the surrounding areas of Velapally village, he added.
With limited rainfall, artificial recharge of ground water structures are erected to augment the ground water potential. The project aims to enhance artificial discharge to ground water through percolation tanks and the techniques used are: desilting reducing evaporation loss by spraying polymer on the tank water surface, by passing the top compact layer and using geoelectrical methods and mathematical modelling for understanding the ground water system.
The studies on water-rock interactions would provide vital data on the chemical evolution of ground water in respect of fluoride, uranium, thorium and heavy metals and the database would help in the design and implementation of suitable measures to contain further pollution of ground water resources, he said.
Further, the institute has developed a simple, low-cost and reliable technique for evaluation of percolation effciency of tanks. The institute has also demonstrated several methods of artificial recharge for different site-specific conditions and methods which are related to the quality problem of drinking water with multiple electrode resistivity and ground penetrating radar techniques.