Abstract

The aim of this study was to evaluate seasonal as well as moderate temporal effects on deep groundwater quality by the dumpsites leachate in the Lahore Metropolitan with a population of about 8 million. Groundwater samples for this study ware drawn from groundwater supply units installed by local government for the provision of drinking water to the residents. The groundwater in down slope regions from municipal solid waste (MSW) dumping sites has been identified by using Inverted Watershed technique. Eleven water supply units have been spotted that fall within the identified leachate plumes. Parameters of pH, turbidity, electric conductivity, total dissolved solids (TDS) and Escherichia coli were determined on water samples from these identified units. The quality analysis indicates that the effect of the leachate is more prominent in the hot and dry pre-monsoon season due to the domination of base flow for recharge of the groundwater, whereas dilution observed in leachate contamination during and immediately after the monsoon rainy season is due to the recharge through seepage of the rain water which dominates the base flow. Variation in the correlation factor between electric conductivity and TDS has been used to estimate constituents of TDS contributed both by rainfall seepage and base flow. An increasing tendency, showing influence of the leachate on the deep water quality, has been observed while analyzing the correlation between distance of the tube wells from leachate sources and measurements of quality parameters.

Key words: Base flow, deep groundwater, down slope regions, landfill leachate, rainwater seepage.