What is river health?

1. Traditionally the assessment of river water quality has been based solel y on the measurement of physical, chemical and some biological characterist ics. While these measurements may be efficient for regulating effluent disc harges and protecting humans, they are not very useful for large-scale mana gement of catchments or for assessing whether river ecosystems are being pr otected. 2. Measurements of aquatic biota, to identify structural or functional inte grity of ecosystems, have recently gained acceptance for river assessment. Empirical evidence from studies of river ecosystems under stress suggests t hat a small group of biological ecosystem-level indicators can assess river condition. However, physical and chemical features of the environment affe ct these indicators, the structure and function of which may be changed by human activities. 3. The term 'river health', applied to the assessment of river condition, i s often seen as being analogous with human health, giving many a sense of u nderstanding. Unfortunately, the meaning of 'river health' remains obscure. It is not clear what aspects of river health sets of ecosystem-level indic ators actually identify, nor how physical, chemical and biological characte ristics may be integrated into measures rather than just observations of ca use and effect. 4. Increased examination of relationships between environmental variables t hat affect aquatic biota, such as habitat structure, flow regime, energy so urces, water quality and biotic interactions and biological condition, are required in the study of river health.