Water utilization by local inhabitants responding to seasonal changes in water quality of river water in Central Kalimantan, Indonesia

Abstract

Acid sulfate soil is one of the most serious regional environmental problems after destruction of the peat layer over pyrite-containing sediment after agricultural land development and deforestation. Sulfuric acid discharged from acid sulfate soil causes acidification of river water. In pyrite distributing areas within the lower basin of the Sebangau and Kahayan rivers in Central Kalimantan, the water of the mainstream of the rivers as well as water discharged from canals into the mainstream in the rainy season show much higher acidity and a higher concentration of sulfate ions than in the dry season. The objective of the present study was to obtain information on utilization of natural water from local inhabitants in the basin with water pollution including sulfuric acid contamination. We held interviews with local inhabitants in sulfuric acid polluted areas in Paduran and Pangkoh as well as areas around Sigi village concerning the sources of water and evaluation of water quality in their habitat. Inhabitants around Sigi mostly depended on well water both in the rainy and dry seasons, whereas the sources of drinking water for inhabitants in Paduran and Pangkoh differed significantly between dry and rainy seasons. River water chemistry showed little difference between the dry season and the rainy season in the Sigi area, whereas river and canal water in the rainy season in Paduran and Pangkoh showed lower pH than in the dry season due to a high concentration of sulfuric acid in the rainy season. Accordingly, river and canal water in the rainy season in polluted areas was not available as drinking or cooking water and thus they avoided using river water for drinking or cooking in the rainy season. Although sulfuric acid concentration in river water both in Pangkoh and Paduran were higher in the rainy season than in the dry season, people in Pangkoh evaluated that water in the rainy season to be better than that in the dry season, whereas people in Paduran evaluated that water in the dry season to be better than that in the rainy season. Paduran people would evaluate water quality by SO42- concentration, whereas Pangkoh people would evaluate water quality by salt concentration because of the lower concentration of SO42- of water in Pangkoh in the rainy season than that in Paduran. Pangkoh people recognized that water contaminated with sulfuric acid was much preferable than water contaminated with sea salt, but they avoided using water contaminated with sulfuric acid in the rainy season. More than 70% of the Paduran people answered that river water presents a high risk for drinking and swimming, whereas only 11% or less of the Pangkoh people knew about the risk of sulfuric acid for human health. The Pangkoh people avoided using river water contaminated with sulfuric acid, but the knowledge about sulfuric acid’s effects on human health was not sufficient. Thus we concluded that although selectivity of water was similar for the local inhabitants of the two villages in polluted area, awareness about the risks of sulfuric acid pollution for human health proved to be quite different between the two villages.