Assessment of water pollution status in Uma Oya, Sri Lanka

Abstract

Uma Oya, which has the highest watershed of the Upper Mahaweli discharges into Rantambe reservoir. Uma Oya may have been polluted as it drains a large portion of agricultural lands. A preliminary study was conducted from April to October, 2007 sampling six randomly selected sites to determine the status of water quality of Uma Oya as baseline data. pH, water temperature, dissolved oxygen, electrical conductivity and turbidity were measured in situ, whereas the processed water samples were brought to the laboratory to determine using standard methods, nitrate-N, nitrite-N, ammoniacal-N, ortho-phosphate, total suspended solids and chlorophyll-a content. Many water quality parameters were within the tolerance limits for fish and other aquatic life. However, the Chlorophyll-a (19.93±10.4 µg/L) was slightly higher than the standard guidelines perhaps due to epilithic algae washed off from bed rocks under high water flow. Total suspended solids (17.87±17.96 mg/l) and turbidity (37.84±59.88) were higher than the standard limits for fish and aquatic life, indicating high suspended solids transported by Uma Oya water. Further studies are required in relation to the cultivation pattern of the water shed to get a clear picture about Uma Oya.