Assessment and monitoring of groundwater quality in semi –arid region

Abstract

The depletion of groundwater resources threatens water security around the world and it is of prime concern. Minimization of the impact of unhealthy drinking water requires monitoring of contaminants and awareness to all stake holders. The work is aimed at developing a Water Quality Index (WQI) to assess and report water quality to policy makers and stake holders for comprehensive planning. This new WQI method assigns individual weights to each sample point under consideration, along with wholesome weights, to account for the relative risk of each contaminant. Water quality is determined for pre and post monsoon seasons. Spatial distribution of water quality is used to estimate the probable impact on affected population. A case study was carried out to validate the method. For this purpose, a total of 163 wells (covering an area of 30,623 square km.) were sampled in a semi-arid region in North India, during pre and post monsoon seasons. Sixteen physico-chemical parameters were measured and six parameters were deemed highly critical due to their coverage and associated health risk. Against the general belief, a rise in the number of wells with permissible limits of Chloride, Nitrite, Fluoride and TDS is observed after the monsoon. The WQI determined by the procedure indicates that only 47% and 59% of the local populace has access to groundwater of acceptable quality during pre and post monsoon seasons respectively.