Abstract:
Excessive pumping and over-abstraction in Jaffna Peninsula, in Sri Lanka, has decreased the ground water levels in the last years. The total area of the Peninsula is 1017 km’ and includes two internal lagoons with an area of 87 km2 and 35 km2 respectively. Climate in the Peninsula is characterised by wet and dry seasons. The recharge to the groundwater in the Peninsula is almost entirely from rainfall pereolation, which occurs mainly on the wet season. During the wet season, most of the rainfall percolation is lost into the sea through the openings on the lagoons and as a groundwater outflow. Therefore, any water management scheme should be based on the effective control of the excess rainfall that is lost to the sea. Barrages/regulators were built in the fifties but the objectives of these schemes never materialised. Currently these control/regulator structures are in a state of disrepair. Two scenarios studied the groundwater levels in the Peninsula, the first by using the existing conditions and the second by controlling the barrages for letting seawater into the lagoons during dry periods and capturing surface runoff from land during the monsoon. In addition, climate change impacts on the groundwater system were considered. All the scenarios were examined by applying a three-dimensional groundwater flow model. Results showed that an excess of 10 Mm’ could be added on the available water in the Peninsula, by controlling the barrages and that climate change could have a positive impact in the region. It can be concluded that lagoons playing a key role on the groundwater storage and could be used effectively as a management option to control the groundwater levels in the Peninsula.
