Abstract
Key words : Small tanks, Dry zone ,Renovation, Aquatic eco system, Aquatic plants in antiquity, multi-purpose institutes and organizations had involved in small tanks renovation in tanks renovation in- whereas at present, Department of Agrarian Development, Irrigation Department, Samurdi Authority, Gamanaguma Project and NGO-s engage in this pursuit. They applied removing soil from tank, renovating tank bund, removing plant cover on the tank, slues repairing, wana (spill) repairing and channel repairing as types of tank renovation.This research focused on identifying the changes of the aquatic plant species living in the tank environment after small tanks Renovation. Small tanks in Sri Lanka are those with an irrigated command area of 80 ha (1 ha = 2.47 acres) or less. The study was conducted with regard to 12 small tanks in Galgamuwa DS division in Kurunegala district where 77 no’s of renovated tanks during the last 15 years are located. Questioner survey, Selected PRA tools and Field Plot Transects were used for data collection and data were statistically analyzed in disclosing the following findings. Distribution of blue water Lilly, Kekatiya, Water hyacinth and Diyameneri are significantly decreased. The invasive alien invasive plants grown in the tank and the surroundings have been a major threat for the existence of the marshland environment and related hydro systems. Many problems have been created by the distribution of invasive aquatic plants especially in the small tanks. The population and distribution of Lilly, Blue water lilly, Plant of hawai, Buduraspasi, Salvenia and Water spinach after the tank renovation negative significantly changed. Lotus plant that was one of the mostly grown plant species before the renovation has become the sixth abundant plant with renovation. Salvieniya has also decreased to the sixth place. Kekatiya and Water hyacinth can be largely seen even after the renovation as they can grow faster. The removal of aquatic plants, specially the invasive plants from the renovated tanks has positively influenced the ecosystem of the tanks. Further, the removals of the plants beneficially influence some aquatic faunal species. Further, the removal of these plants has prevented addition of aquatic organic matter into the tanks and this has beneficially influenced maintaining the dissolved oxygen level in the tank system. Therefore, the reduction in aquatic plants has more beneficial impacts to the tank system.