Many rivers have had some form of modification to their natural flow for services such as water supply and hydropower. This is typically done by impoundment, which is the term for any structure that raises water levels, such as dams or weirs. As the demands for water supply and hydropower increase, it is hard to prevent them from being implemented. However, it is agreed by most that typical modified flows do not sufficiently cater to the needs of downstream ecosystems. As such, more must be done to understand their impacts and mitigate any issues.
Ian Hough, a STREAM researcher, developed a novel, transferable framework to assess a small scale impoundment in North West England, using linked hydro-ecological modelling. The model employed flow velocity measurements and macroinvertebrate sampling data. Predictions of habitat quality were created using established ecological principles, such as the importance of flow heterogeneity (being nonuniform and diverse). The results were then used to design environmental flow regimes, aiming to improve ecological metrics whilst considering the conflicting water demands.
Based on historical flow records, implementing designer flows over 12 months showed increased peak species habitat qualities by 23-26%. Characteristics such as flow heterogeneity were more natural, and 22% water was released from the impoundment. If these outcomes are validated experimentally, there is a great potential for further development and application of this method. The method could also be used in other sites of similar magnitude and geography, so the transferability of the model makes it even more useful if validated experimentally. This could result in fewer negative effects happening due to impoundment.
Full article: Designing an environmental flow framework for impounded river systems through modelling of invertebrate habitat quality, Ian Hough, Philip Warren, James Shucksmith, Ecological Indicators
