Water quality during the rainy seasons and drought seasons in the Garang River Basin (Semarang, Indonesia)

Abstract

The Garang River is the city of Semarang’s primary source of water, particularly for drinking water and other domestic needs. This research attempts to examine the current water quality status of the Garang River Basin by using the Malaysian Water Quality Index (WQI). Six water quality parameters were selected and analysed; DO, BOD, pH COD, NH3-N and TSS. Water sampling was conducted at eight stations based on the Governor Regulation of Central Java No. 156 (2010) on Water Allocation and Water Quality Management of Garang River. Water quality was sampled twice, once during the rainy season (2 January 2020) and once during the drought season (1 September 2020). The findings of the study showed that the water quality status of the Garang River Basin during the rainy season recorded a WQI value of 81 and 92 during the drought season. Both values belong to Class II, which represents clean waters. Three water quality parameters were identified to have exceeded the set standards: the DO, BOD, and NH3-N. Changes in landuse, particularly the clearance of forest areas for agriculture, plantation activities, domestic waste disposal, and wastewater directly from industrial activity and local inhabitants, have all contributed to the Garang River Basin’s deterioration of water quality. However, in the context of water classes, it is shown that the water of the Garang River is suitable to be used as a domestic water supply for local residents but requires further treatment prior to consumption.