Chemical Hydrogeological Study of the Kim River Basin, South Gujarat,India: with Special Reference to Impact of Irrigation on Groundwater Regime.

The groundwater quality in the Kim River Basin, south Gujarat was evaluated for its suitability for irrigation use by setting up a network of 43 observation wells. Seasonal sampling of these wells was carried out for two consecutive years and the groundwater samples were analyzed for various physico-chemical parameters. The aquifer characterization was also done in order to understand the seasonal and spatial groundwater quality fluctuations. Analysis revealed that the pH values of all the samples were alkaline in the range of 7.5 to 8.7 with very little variation on seasonal basis. The Electrical Conductivity showed seasonal variation ranging from 340 to 7700 mS/cm which was attributed to combined effects of aquifer type and extensive irrigation practices in the region. Irrigation water quality indices such as Sodium Absorption Ratio, Soluble Sodium Percentage, Kelly?s Ratio, Schoeller?s Index and Puri Salt Index were applied to the analyzed groundwater samples. The results clearly indicated that the basaltic aquifers in the upstream had good water quality suitable for irrigation in all the seasons. The sedimentary aquifers in the central part of the Basin had slightly moderate water quality owing to solution weathering and thus, not acceptable for irrigation without proper dilution. The lower basin had high potential of groundwater due to presence of alluvial aquifers but the quality of water was unsuitable for irrigation due to high enrichment in various cations and anions.