Water Quality Variation in a Tank Cascade Irrigation System: A Case Study from Malagane Cascade, Sri Lanka

Abstract

Tank cascade irrigation system (TCIS) is a water management practice developed in order to match the nature of the rainfall and landscape in the dry zone of Sri Lanka. The series of interconnected tanks in this system serves multiple functions, including irrigation. This study was carried out to investigate the water quality variation in a tank cascade system and study the role of hydrophytes found in the upper periphery (Thaulla). The Malagane Tank in the northwestern intermediate zone of Sri Lanka was selected for the study. Fairly high levels of nutrients and metal concentrations were recorded in the upstream paddy fields and main inflow of the tank. The concentrations of most of the chemical parameters were showed a decreasing trend while passing the thaulla area which is one of the most important hydrologic regime in a tank system. However, the runoff from the either sides of the tank has polluted the lake water particularly during the rainy season. The hydrophytes in the thaulla area play a major role in the hydrology of the tank system.