Spatial distribution of groundwater salinity at coastal region in Jaffna Peninsula: A case study at Karainagar

Abstract

The supply of drinking water and accessibility of irrigation water at Karainagar divisional secretary division, demands the knowledge of groundwater features, in particular salinity, in order to avoid displacement of people from the area and to uplift the agricultural sector. The scope of this work is to determine the well density, identification of suitable wells for drinking and for irrigation based on the electrical conductivity, and to obtain the spatial distribution of groundwater salinity. All the wells present in Karainagar about 2697 wells were surveyed with the well head parameters and quality data as, type of well, usage pattern. purpose of usage, water withdrawal method, distance from the toilet. depth and diameter of the well, pH and EC during June 2011 to October 2011 and in September 2012 to October 2012 during the most drier period. All the wells were point marked in satellite images of the study area and geo referenced by using Are view 3.2. The surface water storage structures were also marked to increase the storage capacity of the runoff water which enhances the recharge. Layers were produced so as to select suitable wells for drinking and agricultural activity based on the Sri Lankan drinking water standard and irrigation water quality. Most of the wells are protected Wells 66.44%, and non protected dug wells and rube wells are 32,78% and 0.78% respectively Regarding water withdrawal, 67,41% hand bucket, 6.90% electric motor. 13.83% use pulley, 0.74% electric water pump and 0.30% use balance pole are used to extract water from the wells pH of all the wells were under the Sri Lankan drinking water quality standards, as 6.5-8. In case of electrical conductivity 11 61% wells were within the SLS maximum permissible level (3500S) and 76.16% wells were exceeding to limits maximum as high salty and the balance wells were empty. Though 11 61 of the wells were below the drinking water standard, the pumping of water for drinking from these wells source way not possible Because the results of step pumping test showed high electrical conductivity of groundwater was pumping duration due to up corning of salt water. Finally Karainagar ares obviously show the water scarcity for drinking water and for irrigation Only 116 of well water could be used for consumption even though 67 4% of well water extracted by hand bucket, sea water influences the quality of the well water. Hence drinking water should be supplied to the Karainagar area through pipe born water.