Impact assessment of coal mining on groundwater chemistry and its quality from Brajrajnagar coal mining area using indexing models

Groundwater chemistry and quality studies have been carried out in the Brajrajnagar coal mining area to find its suitability for human consumption, domestic use, agriculture use as well as industrial purposes. A total of fifty-four water samples were collected in Polyethelene containers from several surface and groundwater sources during the summer month of May, 2015. Physical parameters like pH, electrical conductivity (EC), total dissolved solids (TDS) and temperature were measured in situ. Major ions (Na+, K+, +, Ca2+, Mg2+, SO42- NO3-, Cl-, F- and HCO3-) and trace elements (B, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Ba and Pb) were analysed in the laboratory. Hydrogeochemical facies present in the groundwater have been identified. On the basis of water chemistry, water quality index (WQI), heavy metal pollution index (HPI), and heavy metal evaluation index (HEI) were determined to ascertain the overall quality of the water for drinking purposes. Suitability of the water for the agricultural purposes was also determined using sodium percentage (Na%), sodium adsorption ratio (SAR), residual sodium carbonate (RSC), US salinity diagram, Wilcox's diagram, Kelly's ratio (KR) and permeability index (PI). The overall groundwater quality studies show that 15% samples are poor in quality for drinking purposes and 43% water samples require special treatment prior to irrigation. The present work will help the local government bodies and mining planners to understand the spatial variation of the quality of groundwater of the Brajrajnagar coal mining area. It will also help to know about the degradation in the water quality and its possible sources and to adopt appropriate monitoring programmes and strategies for protection of the water resources of the region.