Water chemistry of Sebangau River and Kahayan River in Central Kalimantan, Indonesia

Abstract

Water chemistry of two rivers in Central Kalimantan, Indonesia was surveyed in September 2003. Effects from sea salt on the surface water chemistry of the river appeared 94 km upstream from the mouth of the Sebangau River, although little effect from sea salt appeared 45 km upstream from the mouth of the Kahayan River. Water discharged from canals (Paduran, Pangkoh and Pulangpisau) into the mainstream of the Sebangau River and the Kahayan River showed lower pH compared to the mainstream water of the rivers, implying sulfuric acid loading from the canal to the mainstream of the rivers. The ratio of SO42-/Cl-, which was used as a parameter for estimating the contribution of pyritic sulfate to the river water chemistry, showed that the sulfuric acid loading from pyrite oxidation appeared from the river mouth up to 145-179 km upstream in both the rivers.