GEMS-Water Operational Guide

This operational guide sets out harmonised technical procedures for the Global Water Quality Monitoring and Assessment programme coordinated by the United Nations Environment Programme, the World Health Organization, the United Nations Educational, Scientific and Cultural Organization and the World Meteorological Organization. It defines criteria for selecting monitoring stations across rivers, lakes and groundwater, and specifies sampling frequencies, field methods and laboratory analytical techniques for physical, chemical, biological and microbiological variables, including particulate matter. The guide details sample handling, quality control, inter-laboratory comparison, and data validation processes to improve accuracy and comparability. It also establishes standardised formats for data reporting, processing, analysis and periodic global assessment of freshwater quality.