The Spatial Analysis of Water Quality in Batang Natal River Estuary Area, Mandailing Natal Regency, North Sumatra

Abstract

Quoted from various sources, the Batang Natal river is currently in a very critical condition where this clear river has become extremely cloudy due to illegal gold mining activities along the riverbanks, especially starting from the upstream area. As a result, approximately 50 km along the river the water can no longer be used by the people who live along the river and it is estimated that there are 30 villages in the vicinity. The analysis was carried out in this area to see how the impact of mining activities in the upstream area that affects air quality and also the level of sedimentation seen from the final stop of the river, namely in the Batang Natal estuary area. This research utilizes spatial analysis with normalized different turbidity index (NDTI), normalized suspended material index (NMSI), and suspended sediment concentration (SSC) as the method. The results of data analysis show that the water quality at the final stop in the Batang Natal estuary area has decreased in their quality in the last 20 years where the water turbidity index shows a range of yield values ​​from -0.129 to 0.490. The results of processed NMSI data show the distribution of solids in the area studied to increase the estuary and downstream areas of the river. The minimum value that appeared in 2000-2001 was 0.1450 and the maximum value was 0.5693. In 2010-2011 the value obtained is in the range of 0.1592 to 0.6280, while in 2020-2021 it is in the range of 0.2049 to 0.6985. The concentration of suspended sediment in the estuary area of ​​Natal was at levels of 10.28 mg/L to 38.92 mg/L.