Biomonitoring of Health of Chubachu Stream Using Macroinvertebrate Diversity

Biomonitoring, to assess the water quality of the Chubachu stream was conducted using macroinvertebrate diversity as an indicator to determine the level of pollution and the impact of wastewater discharge from settlements along the stream. The study site was divided into two zones based on the density of settlements as dense or sparse, with 3 sampling points in each zone. The assessment was performed using the Biological Monitoring Working Party (BMWP) score system. A total of 693 specimens were collected belonging to 19 families. The study found that the level of water pollution is directly correlated to settlement density. The water flowing through the sparse settlements is substantially lesser polluted compared to a densely populated area. The study found 4.5 – 61500 CFU/100mL of thermotolerant coliform in the area, significantly higher than the permissible limit for drinking water as per Bhutan Drinking Water Quality Standard (BDWQS) & World Health Organization (WHO); which is 0 CFU/100mL. The study also found that the discharge of untreated sewage and dumping waste directly into the stream is the primary source of pollution. Realigning sewage discharge into municipality sewage network, treatment of wastewater, and proper management of waste by residents living along the stream can help reduce pollution and improve the water quality