WP5: Develop a risk assessment guideline for stream managers
Which streams are most vulnerable to losing their self-purification capacity due to drought (regarding duration and frequency of drying out, ambient nutrient and OM concentrations, and sediment structure)? How do current risk assessments for streams need to be adapted to indicate possible threats for water quality there?
Based on our results from WP2 and WP3, we will identify factors which have the power to increase or decrease the resilience and resistance of the sediment surface and/or the hyporheic zone to desiccation. Such factors may be external, like the duration and frequency of the dry phase, or internal, such as sediment structure and resulting moisture content, ambient nutrient and organic matter concentrations, or shading and resulting water temperature. Internal factors determine the vulnerability of the respective reaches to suffer severe reductions of their self-purification capacity – and thus a possible deterioration of water quality – due to drought. We will develop a guideline which supports stream managers to estimate this vulnerability based on few easily measurable parameters. For that purpose, we will categorize the studied stream reaches according to their vulnerability to drought impacts. Based on our results and on experiences of the SMIRES consortium, we will include suggestions for a monitoring scheme for intermittent streams in this guideline.