Effect of pumping on temporal changes in groundwater quality

Pumping studies were conducted at five sites distributed over a 3000 ha area in the Gohana block in Haryana state of India. The project area is a part of the Indo-Gangetic plain and lies in a topographical depression susceptible to waterlogging, soil salinity and groundwater pollution from surrounding industrial towns. The crop productivity of irrigated lands in the project area is declining due to secondary salinization and shortage of surface irrigation supplies forcing farmers to depend on groundwater abstraction through shallow tubewells. Three wells of 30 m depth and two of 60 m depth were developed in the project area and the effect of pumping on temporal changes in groundwater depths and quality was studied over a period of 72 h. Groundwater samples, collected from different depths up to 30 m at each site while installing piezometers and at different times during pumping tests, were analyzed for electrical conductivity (EC), pH, ionic composition and heavy metals like arsenic (As), copper (Cu), zinc (Zn), manganese (Mn), cadmium (Cd), nickel (Ni), lead (Ph) and chromium (Cr). The results indicated varying values of EC, pH, sodium adsorption ratio (SAR) and residual sodium carbonate (RSC) which, in an average sense, were much above the limits prescribed for use of water for irrigation. Of the heavy metals, groundwater was heavily contaminated with As, Pb, Cd and Ni having maximum concentrations of 27.5, 1.53, 0.12 and 1.46 mg/l. respectively, which are much higher than maximum permissible limits, Contaminants had variable times of peak concentration, some with multiple peaks, denoting non-uniform contaminant concentrations and possibly different adsorption characteristics. The results emphasize that groundwater in the project area needs to be analyzed not only in respect of conventional quality parameters but also for heavy metal contamination for their safe use in agriculture. The source or the cause of such serious groundwater pollution problems in the region must be identified to minimize the hazardous effects of using such waters on a long-term basis. (C) 2002 Elsevier Science B.V. All rights reserved.