Water: Urban settlements along the Pachu in Paro, Wangchu in Thimphu, and Punatsangchu in Punakha and Wangdue are affecting the water quality for both the main rivers and their tributaries that flow through these towns.
This was confirmed by the first scientific water tests two scientists, Bernard Sweeney and Anthony Aufdenkampe from Stroud Water Research Centre (SWRC), and Beth Fisher from the University of Minnesota in the United States conducted.
The study however states that although the impact of the large population centres is noteworthy and substantial, the aquatic ecosystems downstream were not dead and still contained substantial populations and communities of aquatic organisms.
The reaches of streams and rivers upstream of the population centres seem to have good water quality and diverse, functional ecosystems and, as such, could serve to provide a local source of aquatic organisms to downstream impacted areas if the impaired water quality of those reaches were mitigated.
The scientists conducted physical, chemical and biological assessments of the three rivers and selected streams in November last year.
Waterkeeper Alliance, which works with Clean Bhutan on a project, Thimchu Waterkeeper invited the team for the study.
The preliminary report was based on multiple sources of data, both qualitative and quantitative. For qualitative study levels of E. coli, total coliform bacteria, and nutrient chemicals such as ammonia, nitrite, nitrate, and phosphorus in the water were measured. Data on macro invertebrate community structure was collected for quantitative study.
E. coli and coliform bacteria are commonly found in the faeces of humans and other animals and could indicate a possible presence of harmful, disease-causing organisms.
E. coli and total coliform bacteria were chosen because their direct connection to human pathogens from faecal waste contamination. The United States Environmental Protection Agency (US EPA) and other governmental agencies throughout the world have developed drinking water and ambient water quality standards using these bacteria, the report stated.
Nutrients such as ammonia, nitrite, nitrate, and phosphorus were measured because their concentrations are elevated by human sewage, animal waste and agricultural fertilizer runoff and as such can indicate the presence of other human pathogens i.e. viruses.
“We selected aquatic macro invertebrates such as insects, worms, crabs, shrimp and snails, because their diversity indicates water quality integrated over months to years,” the scientists said.
The team also selected open source data-logging and wireless communication technologies as a demonstration of relatively low-cost environmental sensing possibilities to measure basic water properties every five-minutes and share that data online to the public in near real time.
The team set up three wireless sensor stations to record water quality along the Wangchu.
“These approaches complement one another to provide a holistic, sustainable path for widespread expansion of water quality monitoring efforts and data in Bhutan and other nations throughout the world,” the report stated.
In general, lower water quality was indicated by reductions in the abundance of pollution sensitive insects along with increased densities of E. coli or total coliform bacteria and increased abundance of certain chemical nutrients such as ammonia and nitrates.
The relative degree of impact of the population centres appears to differ in each district. The impact appears to be more severe in Paro and Thimphu than in Punakha given that all three insect groups were present at both sites downstream of Punakha and Wangdiphodrang whereas one of the three groups (Plecoptera) was missing downstream of Paro and Thimphu.
Levels of E. coli, total coliform bacteria, and ammonia or all three were found generally higher downstream of Paro and Thimphu than below Punakha and Wangdiphodrang.
Clean Bhutan Executive Director Nedup Tshering said the quality of water is not due to recent activity.
“This result indicates that it is accumulation of pollution over several years that has been drained into the river,” he said.
Thimchu Waterkeeper will be collecting one more sample before April this year. “The same group of scientists will repeat tests to confirm the status of water quality and they will submit the recommendations to the government for consideration,” Nedup Tshering said.