Browsing by Author "Jayawardhane, D.T."

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    INVESTIGATION OF THE EFFECTIVENESS OF UPPARU SALT BARRAGE IN JAFFNA PENINSULA (3 Stage)
    (Uva Wellassa University of Sri Lanka, 2015) Rupathasan, N.; Udagedara, D.T.; Jayawardhane, D.T.
    The Jaffna Peninsula is located in the northern Sri Lanka. The total area of the Jaffna Peninsula is and demarcated three internal lagoons such as Thondamanaru, Upparu and Valukiaru. The first two lagoons comprise of an area of 77.6 km and 25.9 km . They are connected to the sea and drain an area of 518 km . Majority of the local community of the area is depending on agriculture and fishing. Groundwater is the main source for people in Jaffna Peninsula for domestic and agricultural activities. According to the field observations even people having their own wells, majority of them are affected by salt water intrusions. Therefore, they depend on the common water supply given by the government for drinking purposes, whereas some people still depend on groundwater sources. Recently, barrage was constructed as a salt water exclusion bund to convert the salt water in lagoon Upparu to fresh water lake. This is expected to improve available water resources of the peninsula, both in recharging the underground storage (Sukanya, 2012). This research is focus of the area from the fringe of the lagoon into the land extending around 2 km. Major aim of the research is to evaluate the effectiveness of the barrage by delineating the salt water intrusion pattern especially in the west and northwest areas of the lagoon. Methodology Existing aquifer types, geology and topography were studied with the help of available resources and monitoring was done in the area. Wells were selected in a circle to the fringe of Upparu lagoon. The areas coming under study are parts of Nallur, Kopay and Chavakachcheri divisional secretariat divisions. Electrical conductivity (EC) of the groundwater was measured during wet and dry seasons. The wells in which EC show a sudden change was selected for further chemical analysis (sodium and chloride). In addition, both wet and dry season sixty eight (68) shallow well samples were selected for sampling. Water samples were collected in PETF bottles, acidified and capped tightly. Water samples were analyzed for Na using Varian Atomic Absorption Spectrometer (AAS 240 series) facility available at the Uva Wellassa University. Chloride was measured with argentometric method. Spatial distribution of the chemical & physical parameters in the groundwater was interpolated using Inverse Distance Weighted method available in Arc GIS 9.3 software. Results and Discussion Results of this study show that EC values for groundwater in the study areas varies between 574 µS/cm and 23,470 µS/cm in wet seasons and between 544 µS/cm and 22,810 µS/cm in dry seasons. Element chloride values range between 449.8mg/L and 7,197.7 mg/L in wet seasons and between 949.7 mg/L and 4,098.7 mg/L in dry seasons. Sodium values vary in between 38.3 mg/L and 802.9 mg/L in wet seasons and between 26.7 mg/L and 648.4mg/L in dry seasons.
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    Investigation of the Effectiveness of Upparu Saltwater Barrage in Jaffna Peninsula, Sri Lanka (4th Stage)
    (Uva Wellassa University of Sri Lanka, 2016) Muraly, K.; Jayawardhane, D.T.; Udagedara, D.T.
    Groundwater is the prime source of water for the people in Jaffna Peninsula. Saltwater intrusion into aquifers has been a persistent issue caused by excessive extraction of freshwater. In order to overcome the groundwater scarcity and quality issues, a barrage has been constructed as a saltwater exclusion bund expecting to convert the saltwater lagoon into a freshwater lake. Major aims of this study are to evaluate the effectiveness of the barrage by delineating the salt water intrusion patterns in groundwater and to study the variation of groundwater types recorded after the barrage construction. Electrical conductivity (EC) and water level of the wells were measured in the field. Groundwater samples were collected from 66 wells during the wet season. Water samples were analysed using Atomic Absorption Spectrometer (AAS) and Spectrophotometer to determine the concentrations of sodium, magnesium, calcium, potassium, chloride, sulphate and bicarbonate. Results indicate that EC of groundwater varies between 403 — 20760 tS/cm. Chloride, sodium, calcium, potassium, magnesium and bicarbonate concentrations are between 7 — 497 ppm, 0.09 — 986 ppm, 0.6 371 ppm. 0.86 —125 ppm, 0.52 —167 ppm and 10 — 1464 ppm respectively. Spatial distribution of the groundwater composition shows that the fringe of the Upparu lagoon which is far from the barrage is having better quality water than the groundwater close to the barrage. Availability of groundwater has significantly increased after barrage construction. It has been noted that if barrage function properly the groundwater in the fringe of the lagoon will become freshwater soon. Comparing with the results of past analyses it can be concluded that barrage system is slowly recovering to produce freshwater. Keywords: Saltwater barrage, Upparu Lagoon, Saltwater intrusion