Wastewater Pollution Indicator - Basin level aggregated BCUs (weighted scores based on population and area) - EPI (Environmental Performance Index)

The Wastewater Pollution indicator measures the estimated levels of wastewater treatment in Basin Country Units (based on national data), rather than absolute volumes of wastewater polluting waterways. This gives an indication of the risks from pathogens which may be highly relevant to vulnerable populations at local scales. The scores are aggregated at basin-scale to give an indication of threats stemming from poor wastewater treatment performance on a basin level. This indicator is largely based on data and methodology from the Wastewater Treatment Performance indicator developed by the EPI (Environmental Performance Index) team at The Yale Center for Environmental Law & Policy (Malik et al. 2015). This indicator compiles wastewater treatment statistics for 183 countries and was deemed to be the most comprehensive, up to date data source available. EPI Wastewater Treatment Performance Indicator is based on two metrics: wastewater treatment and connection rate (Malik et al. A global indicator of wastewater treatment to inform the Sustainable Development Goals (SDGs), Environmental Science & Policy, Volume 48, April 2015, Pages 172–185). Wastewater is defined as “water that has been used by households, industries, and commercial establishments that, unless treated, no longer serves a useful purpose and may contain contaminants. The EPI Wastewater Treatment Performance indicator is based on two variables: a) wastewater treatment - the amount of wastewater that is treated within a country relative to the amount of wastewater that is collected, generated, or produced; b) connection rate – the population connected to municipal sewerage systems relative to the population living in the country. The indicator assesses national wastewater treatment performance, normalizing treatment scores by the population connected to municipal sewerage systems, using following calculation: “wastewater treatment level x connection rate“ Underlying data sources: - Pinsent Masons Water Yearbook (2013) - United Nations Statistics Division (2011) - OECD (2013) - FAO (2013) - National level data gap-filled from reports and on national statistics websites