Impact of canal recharge on groundwater quality of Kolayat area, district Bikaner, India

Abstract

Rajasthan is one of the water scarce states of India where the annual average rainfall varies from less than 100 to 1000 mm.Kolayat area of district Bikaner located in western part of the state, receives average annual rainfall of 275 mm.Owing to the less rainfall of this low magnitude, the water availability problem in the Kolayat area is critical in comparison to many other parts of the state.The water requirement, of the area, is mainly met by Indira Gandhi Nahar Project (IGNP) canal.The groundwater quality of the area through which IGNP canal passes has been studied to understand the effect of canal recharge on groundwater and subsurface movement of recharge pathways.The canal trends in NE-SW direction and flows towards SW.The study has been carried out across the canal 40 km in the eastern and 20 km in the western direction.The depth to water varies between 10 and 55 m bgl.The water levels are shallow in western direction and upto Bajju in eastern direction from the canal.The water levels become deeper as one moves towards eastern direction.This suggests that the groundwater regime receives recharge from the canal towards western direction and upto Bajju in eastern direction.The groundwater flow directions obtained from water table contours also reveal the presence of groundwater mound in the vicinity of the canal.The EC of the canal water is 302 μS/cm where as the EC of groundwater varies from 563 μS/cm to 23600 μS/cm.The EC of groundwater along the canal varies from 563 μS/cm (Bajju) to 1916 μS/cm except Modayat where as EC is high away from the canal.Water quality analysis confirms the same result as interpreted from groundwater contours.The groundwater of the area has high calcium, magnesium, sodium, potassium, chloride, sulphate, they range upto 634, 787, 5890, 1015, 7908, 2650 mg/L respectively.Further, fluoride in the areas around Chak 4 GMR (3.8 mg/L), Bajju (1.93 mg/L), Godu Krishi farm (4.12 mg/L), Godu village (1.93 mg/L) exceeds the permissible limit for drinking purpose.The study also reveals that recharge from IGNP canal has a long term influence in the study area where groundwater is withdrawn for various activities.