Increasingly, in urban water resource management the consideration of stormwater impacts on water resources gains in importance. Among stormwater discharges the impact from combined sewer overflows (CSO) plays a prominent role. The dynamic character of the discharge events lead to particular stress on the water bodies.

The project MONITOR-1 covers the preparation of a concept for combined sewer overflow (CSO) monitoring in Berlin. The monitoring itself shall be conducted from 2009 on in the frame of the project MONITOR-2 based on the outcomes of MONITOR-1. Objectives of the monitoring are based on long-term interests: Analysis of pathways of stormwater-bound pollutants from urban zones to the natural water body, analysis of the impact of CSO on receiving water quality, better process understanding and process description in modelling (strong linkage to project SAM-CSO). The focus will be on:

• High dynamic processes like Oxygen consumption following the discharge of easily degradable organic substances and fish toxicity by unionised ammonium.

• Trace substances (emerging pollutants).

The monitoring will cover a river stretch in the centre of Berlin (type of water body: stagnant lowland river) and the significant CSOs that discharge to that river stretch. Simultaneous monitoring of both, processes at CSOs and in the receiving water will be planned (hydraulic and physical-bio-chemical).