Investigation of salt water intrusion along the Bolgoda estuary

Abstract

Saltwater intrusion is a natural process that occurs in virtually all coastal water bodies. It causes various effects resulting high breeding of fish, prawns, water hyacinths and drinking water problems due to contamination of fresh water with saline water. Present study, focuses on the intrusion of saltwater along Bolgoda estuary. Objectives of this research are to determine the evidence of saltwater intrusion along the Bolgoda estuary and identify the social and ecological problems related thereto, such as the effects on riparian plants and aquatic life and the adoption of mitigatory measures. Investigation was carried out by measuring water quality parameters (Conductivity, pH, Dissolved-Oxygen, Temperature and Oxidation- Reduction Potential) along the estuary water in vertical profiles as well as water in nearby monitoring wells. Observations were made on different tidal periods to study the rate and extent of saltwater intrusion along the river. These vertical profiles of water quality parameters were taken along the river approximately around 50m intervals, starting from Panadura estuary towards the North direction of the estuary up to about 12 km. Results shows salt water intrusion is a prominent feature during the neap tide period than the spring tide period. Therefore, tidal variation does not control salt water intrusion for our sampling periods. However, salt water intrusion is lower in the periods with higher rainfall period. Therefore rainfall and possibly evaporation is the main controlling factor of the salt water intrusion at Bolgoda Estuary. Salt water intrusion in this estuary is an advantage to the surrounding community since salt water removes water hyacinth, and promotes prone farming.