The objective of this study is to assess the present status of saltwater intrusion in the proximity of lagoons (Vadamarachchi and Uppuaru) in Jaffna, Sri Lanka. Ten villages along the periphery of the said lagoons were selected for a questionnaire survey (n=150) and groundwater quality analysis. The results revealed that the villages; Thondaimanaru, Atchuveli, Ariyalai, Kaithady and Karanavai are less affected (<33%) whilst Chemmani, Madduvil, Navatkuli, Irupalai and Neerveli are highly affected (>60%) in terms of intolerable level of salt content in the sandy aquifer. In Irupalai alone, more than 80% of the wells are highly affected where more than 80% of the wells monitored are exceeded the tolerable limits of EC (>2.5 S/cm) and salinity (>900 ppm), thus unsuitable for human consumption. The field mapping of water quality parameters (EC and salinity) revealed that the villages influenced by Vadamarachchi lagoon was lesser affected (<33%) than the villages influenced by Uppuaru lagoon. There is a trend of decreasing salinity from boarder of the lagoons to inland. As an initiative, water quality monitoring, establishing monitoring wells, and educating the people about adverse effects of over pumping of water are essential to reduce the saltwater intrusion in the area. Renovation of existing saltwater barrages would be an appropriate solution to enhance the groundwater quality in future.

An attempt was made to identify, validate the village tank cascade systems (VTCSs) and study the water flow from one village tank to another in each VTCS in the eight Agrarian Service Centre (ASC) divisions in the Vavuniya district from October 2017 to December 2018. VTCS contributes a significant share of available water resources for the livelihoods of households in the Vavuniya district. The 1:10,000 topographic map of the Survey Department, satellite images and the digital elevation model were used to identify the cascades and flow direction map for the study area using ArcGIS 10.2.2. Among 756 village tanks in the district, 80 VTCSs comprising 514 village tanks were identified, and only 69 cascades were validated in the field. In addition, this study identified 111 isolated village tanks without connecting with other village tanks and 131 abandoned village tanks. Further investigation is recommended to explore the possibilities of increasing the cascade areas in the study area by connecting isolated tanks with VTCSs. Initiation taken toward rehabilitation of cascades would enhance the livelihood of farm households in the Vavuniya district and lead to sustainable water resource management.

This study was conducted to assess the efficiency of aquatic macrophyte -Colocasia esculenta to treat the rice mill wastewater especially for (suspended and dissolved) solids, organics, and nutrients in a pilot scale vertical subsurface flow constructed wetlands. Two units of constructed wetlands were assembled with growing media comprised of three layers (soil-sand-gravel), one as control (without macrophyte) and the second as experimental unit (with macrophyte). The collected inlet and outlet samples were analyzed for various water quality parameters and statistical analysis was done to study the significance of Colocasia esculenta in wastewater treatment. The results revealed that Colocasia esculenta was effective in reducing suspended solids (34.5% ± 15.9), BOD5 (53.0% ± 5.7), COD (50.3% ± 11.1), nitrate (55.7% ± 13.5) and phosphate (76.1% ± 20.5) from the wastewater. Besides this, the growing media itself significantly reduced suspended and dissolved solids through sedimentation. Authors claim the Colocasia esculenta was observed to be efficient in treating rice mill wastewater compared to Canna indica for the same experimental conditions. In addition, long term operation of this experiment is needed to study the interactive role of microorganisms to make the treatment system highly efficient, cost effective and sustainable.