Pengaruh Aktivitas Masyarakat terhadap Kualitas Air Berdasarkan Musim di Danau Toba Kecamatan Silahisabungan Kabupaten Dairi

Abstract

Water quality plays a crucial role in sustaining the functions of aquatic ecosystems as vital resources for human and ecological life. Lake Toba, the largest volcanic lake in Southeast Asia, is currently facing water quality degradation due to increasing anthropogenic activities in its surrounding areas. This study aims to analyze the influence of human activities and seasonal variation on the water quality of Lake Toba and to determine its water quality status using the Pollution Index and STORET methods. The research was conducted at four observation sites, each representing different types of anthropogenic activities: fish farming, residential settlements, schools, and tourism facilities such as hotels and restaurants. Sampling was carried out during two different periods, the rainy season (January 2025) and the dry season (March 2025), using the grab sampling method. The analyzed parameters include temperature, Total Dissolved Solids (TDS), turbidity, pH, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), phosphate, nitrate, and fecal coliform. Data were processed using quantitative analysis. The findings reveal that human activities and seasonal variation have a significant influence on the water quality conditions of Lake Toba, particularly on several sensitive parameters. Nitrate levels varied significantly between different activity-based locations, while turbidity, TDS, pH, DO, and phosphate levels showed significant differences between the rainy and dry seasons (p-value < 0.05). Several parameters, including BOD and phosphate, exceeded the quality thresholds established by Government Regulation No. 22 of 2021. Based on the Pollution Index method, the water quality status at all stations in both seasons falls under the category of lightly polluted. Meanwhile, the STORET method classified three stations as moderately polluted and one station as lightly polluted. The differing results between the Pollution Index and STORET methods demonstrate that the analytical approach used can influence the interpretation of water quality status, highlighting the importance of aligning the chosen method with the intended purpose of water quality assessment.