Mapping groundwater quality for irrigation in Punjab, North-West India, using geographical information system.

The state of Punjab-a part of the Indus basin of the Indian subcontinent has an excellent net work of irrigation facilities. However, due to intensive cultivation it is facing a major problem with respect to quality of groundwater for irrigation. In the present investigation, geo-referenced groundwater samples were analysed to map water quality using geographical information system. Electrical conductivity varied from 0.418 to 5.754 dS m with an average of 1.365 dS m. The carbonate ranged between 0 and 120 mg L, whereas bicarbonate ranged from 5 to 1,000 mg L. Chloride varied from 7 to 2,347 mg L. Calcium plus magnesium ranged from 12 to 1,216 mg L with a mean value of 169 mg L. Sodium adsorption ratio ranged between 0.0 and 34.78 with an average of 2.66 meq L. Residual sodium carbonate varied from 0 to 21.30 meq L with a standard deviation of 2.24. The Geographic Information System (GIS)-based mapping indicated that water in suitable category spatially covered 45.7 % of the state which is located mostly in the sub-mountain (Siwalik Hills), north-eastern undulating and piedmont and alluvial plain agro-eco-subregions. Marginally suitable groundwater spatially covered 46.1 % in the central alluvial plain and south-western alluvial plain agro-eco-subregions. Unsuitable groundwater covered 8.2 % of the state, mostly in the erstwhile sodic soils areas in the central alluvial plain and south-western alluvial plain agro-eco-subregions. GIS-based maps are effective in identifying hot spots which need immediate attention and call for strategic planning for sustainable management. [ABSTRACT FROM AUTHOR]