Groundwater quality mapping using GIS: A study from India's Kapgari watershed

© 2007 Wiley Periodicals, Inc. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/tqem.20130 Groundwater is an essential source of drinking water in rural India. Contamination of groundwater (resulting from human activities or from inherent aquifer material composition) reduces the supply of safe drinking water, posing a threat to public health and a challenge to water managers and strategists. Groundwater quality maps are effective for identifying locations that involve the threat of contamination. The study described here uses geographic information system (GIS) technology to map groundwater quality for drinking and irrigation purposes, utilizing data generated from chemical analysis of water samples collected from the area under study. The study area in this case is the Kapgari catchment in West Bengal, India. To evaluate pollution within the watershed, we used a vector-based GIS software package called ArcInfo, along with water quality analysis data. The locations of wells used for groundwater sampling were obtained by using a handheld global positioning system (GPS) receiver. The final groundwater quality map that we created pictorially represents groundwater zones as “desirable” or “undesirable” for drinking and irrigation purposes. Our spatially integrated d r i n k i n g w a t e r quality map indicates that almost 80 percent of the study area is undesirable for drinking purposes. By contrast, the irrigation water quality map shows that over 93 percent of the study area can be considered suitable for irrigation, with salinity (measured in electrical conductivity) of less than 0.75 decisiemens per meter (dS/m). In our study, we also assessed the temporal variation in concentrations of agriculture-generated ions in the shallow groundwater of the Kapgari watershed.