River Flow and Catchment Monitoring

Observations of catchment conditions are essential for many hydrometeorological forecasting applications. Examples include measurements of water levels in rivers, lakes and reservoirs and of evapotranspiration, snow cover and soil moisture at a catchment scale. Additional information may be required for water quality applications. This chapter discusses the main real-time monitoring techniques used including float-in-stilling well, bubbler, ultrasonic, radar and pressure transducer devices for monitoring river levels, and index velocity and digital imaging techniques for measuring flows. It also considers the related areas of current meter and ADCP flow gauging, rating curve development, hydrometric data management, network design and telemetry systems. Other techniques considered include satellite and cosmic ray neutron sensor observations of soil moisture, scintillometers and eddy covariance devices for measuring evaporation, and ultrasonic sensors for measuring snow depth. Citizen science and crowdsourcing techniques are also discussed and low cost options for instrumentation. Examples are presented for the USGS river gauging network and ALERT telemetry systems from the USA and low cost sensors used in Nepal and Peru.