Water Quality Monitoring and Assessment of Groundwater - Technical Guidance

This technical guidance document is part of a series addressing monitoring and assessment of freshwater resources. It explains the hydrogeological characteristics that control groundwater quantity, storage, movement and chemical composition, and describes how these characteristics inform the design of monitoring programmes. The document outlines the occurrence and behaviour of groundwater within different aquifer types, including the influence of porosity, permeability and hydraulic gradients on groundwater flow. It describes natural groundwater quality and the physico-chemical parameters commonly measured to assess it, together with major threats arising from microbial pollution, nutrients, salinisation, industrial activities and naturally occurring substances. The document also examines contaminant transport processes in groundwater systems and their implications for monitoring. Practical guidance is provided on the selection of monitoring parameters, sampling methods, monitoring frequency and network design, as well as on the construction and use of monitoring wells to generate reliable data supporting groundwater assessment and management.