Groundwater is often a forgotten resource in Sri Lanka. Despite the fact that groundwater covers over 90 % of Sri Lanka's coastal freshwater consumption. Groundwater is very important and is the only source of fresh water in the northern coastal belt of Sri Lanka, especially in the sand stretches located between brackish water lagoons and the sea. It provides water for domestic use as well as for agriculture. Saltwater intrusion from both lagoon and sea can lead to lesser and lesser freshwater lens for the domestic purposes. Due to the saltwater intrusion, hundreds of acres of lands, hundreds of wells are in abandon stage at Jaffna Peninsula. Therefore this study was conducted to assess the extent of the saltwater intrusion at Vadamaradchi lagoon area.