Within the framework of the International Rhine Action Programme and the EC ACE-Programme in the field of the environment (regulation EC.224/87) the sensitivity and reliability of biological early warning systems are being tested. The effectiveness of these systems for continuous water quality monitoring is being assessed, using surface water and industrial effluents.

The systems tested are a fish and a waterflea early warning system. From the results it is concluded that both types of biological early warning systems in combination with physico-chemical monitoring increase the effectiveness of monitoring pollution levels in surface water. Fish early warning systems can be important tools in reducing water pollution by industries.