The researchers used a GIS tool to find areas polluting the Bagmati River in Kathmandu valley, Nepal. They collected data on pollution sources like people, animals, and industry, then combined it to see how much pollution each area was causing. They found that Kathmandu, Lalitpur, and Bhaktapur are major polluters, with people being the main cause of pollution. The river gets a lot of pollution from these areas, especially phosphorus from cremations along the riverbanks. Despite some pollution from industry and land use, most of the pollution comes from these municipalities.