WATER QUALITY IN SIAK, A TIDAL BLACK WATER RIVER IN CENTRAL SUMATERA, INDONESIA

摘要

The Siak River is a blackwater river in Riau Province, Central Sumatera. It has a unique character because of its very gentle slope, making it influenced by tides up to ± 200 Km from the river mouth. There are so many activities around the river, such as housings, river transportation, industries and conversion of peatlands into oil palm plantations which affect the quality of Siak River. The aim of this research was to specify the water quality of the Siak based on physical and chemical parameters at high and low tides to determine the relationship between tidal movement and other factors that affect the water quality of Siak River. The study was conducted in December 2015 and July 2016. Water samplings were carried out at low and high tides along the river, with parameters of physicochemical such as, pH, temperature, dissolved oxygen, salinity, BOD, COD, nitrate, nitrite, ammonia, and phosphate. The results showed that the water quality of the Siak River for parameters of pH (4.87-7.63), DO (0.52- 5.83 mg/L), BOD (6-49.60 mg/L), COD (36.47-123.20 mg/L), nitrite (0.11-0.23 mg/L) and ammonia (0.02-1.23 mg/L) were high. The value of pH and DO of Siak River for both of tidewater was low, however, the value of BOD, COD nitrite and ammonia was high that they were influenced of matter organic from peat swamp, domestic waste and industrial sewage. In general, physicochemical parameters of Siak River were fluctuated, depending on tides and seasons.