Characterization of Irrigation Water Quality of Chunnakam Aquifer in Jaffna Peninsula

Chunnakam aquifer is the main lime stone aquifer of Jaffna Peninsula. This  study focused on characterization of Chunnakam aquifer for its suitability for irrigation.  Groundwater samples were collected from wells to represent different uses such as domestic,  domestic with home garden, public wells and farm wells during January to April 2011.  Important chemical parameters, namely electrical conductivity (EC), chloride, calcium,  magnesium, carbonate, bicarbonate, sulfate, sodium  and potassium were determined in  water samples from 44 wells. Sodium percentage, Sodium adsorption ratio (SAR), and  residual Sodium Carbonate (RSC) levels were calculated using standard equations to map  the spatial variation of irrigation water quality of the aquifer using GIS. Groundwater was  classified based on Chadha diagram and US salinity diagram. Two major hydro chemical  facies Ca-Mg-Cl-SO 4 and Na-Cl-SO 4 were identified using Chadha diagram. Accordingly, it  indicates permanent hardness and salinity problems. Based on EC, 16 % of the monitored  wells showed good quality and 16 % showed unsuitable water for irrigation. Based on  sodium percentage, 7 % has excellent and 23 % has doubtful irrigation water quality.  However, according to SAR and RSC values, most of the wells have water good for  irrigation. US salinity hazard diagram showed, 16 % as medium salinity and low alkali  hazard. These groundwater sources can be used to irrigate all types of soils with little  danger of increasing exchangeable sodium in soil. However, 2 % of the wells are not  suitable for irrigation due to very high salinity and sodium hazard. Tropical Agricultural Research Vol. 23 (3): 237-248 (2012) DOI: http://dx.doi.org/10.4038/tar.v23i3.4661