Spatial and temporal variation of groundwater quality and its suitability for irrigation and drinking purpose using GIS and WQI in an urban fringe

Abstract

This study is aimed at evaluating the groundwater quality within the urban reach of Gridhumal river sub-basin. 29 groundwater samples were collected with different categorization during post-monsoon (POM) and summer (SUM) seasons respectively. Various physical and chemical parameters viz., pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Hardness (TH), Total Alkalinity, cations such as, Ca2+, Mg2+, Na+, anions such as NO3−, SO42−, F−, Cl− were analyzed and were compared with the standard guidelines recommended by WHO, ICMR, BIS. GIS techniques were used to find out the distribution of groundwater quality on land use pattern. Results indicated that the EC, TDS, TH, Na+, Cl−, NO3− level in groundwater samples was above critical limits, and it was found to be very high in wastewater irrigated areas in the urban reach of Gridhumal river sub-basin. Geochemical analysis of groundwater samples shows the predominance of Na-Cl and NaHCO3 types. The geochemical data was interpreted using WQI for drinking water quality and were found not suitable for drinking purposes. With Wilcox diagram, only 30% and 21% groundwater samples show suitability for irrigation for post monsoon and summer season. The US Salinity Laboratory Staff plot depicted that all the post monsoon groundwater sources are C3-S3, C4-S4 type and C4-S4 for the summer season. 17% samples show C3-S1 type for both the season. From the HC analysis in the groundwater samples have been classified into two groups, one is ionic and another metals group. PCA results revealed the existence of seven significant principal components indicating how processes like rock-water interaction and anthropogenic activities influence groundwater quality. Seven factors which together explain 83.33% and 77.85% of the total variance in the post monsoon and summer season respectively. In comparing heavy metal contents present in water samples with BIS/WHO standards, Pb, Cr and Cd concentrations were found to be present above the maximum permissible limits and were found in the following order Cd < Pb < Fe < Cr < Mn < Zn. By results, it is concluded that groundwater is not suitable for irrigation and drinking purposes due to long term use of wastewater, anthropogenic activities, over-extraction of groundwater and changes in land use pattern.