Hydrodynamics of fish-friendly engineering structures in river systems: quantifying attraction mechanisms in terms of hydrodynamic metrics

In the UK, 43% of river habitats are classified as severely modified and there is continued pressure for further urban development. Furthermore in-stream structures (weirs, culverts, sluice gates, low head hydropower schemes etc) have led to fragmentation of river systems. With thousands of artificial structures in the UK and the on-going implementation of the Water Framework Directive (WFD) throughout Europe, many waterbodies are failing ecological targets due to inadequate fish passages. The negative effects of obstructions in rivers on migrating fish include delays to upstream spawning grounds or downstream habitats, increased predator exposure and injury. Globally, river obstructions have led to a reduction or even extinction of migratory fish populations.

A major requirement of the EU WFD is that fish migration remains “undisturbed” and therefore in the case of run-of-the-river hydropower schemes, fish passes must be constructed to facilitate the free passage of fish. In a fish pass or ladder, a water jet attracts fish to the entrance, but this needs to be clearly discernable from the discharge associated with the weir/hydropower device. Despite this, and construction costs per fish pass up to £1M, little is known about the necessary magnitude of the water jet and the near-pass velocity shear and turbulence ‘attraction’ conditions or indeed the conditions needed to repel fish away from the obstruction.

This studentship aims to characterise the hydrodynamic conditions of ‘successful’ fish passage structures and examine cheaper ways to retrofit existing structures to minimise fish passage delay. This will be achieved by near-pass velocity/turbulence characterisation at selected field sites. These findings will be transferred to the laboratory and through hydrodynamic-fish behaviour flume experiments, new retrofitting options will be tested. This will enable a protocol for fish attraction based on hydrodynamic metrics to be developed and enable regulatory authorities alterative options to fulfill the WFD requirements.

This project will involve both fieldwork and laboratory studies spanning experimental fluid mechanics, hydrometric design and fish biology. Training will be provided in experimental design, data analysis (Matlab, Tecplot, VSA and R), specialised techniques such for velocity and turbulence characterisation using Acoustic Doppler velocimetry and Particle Image Velocimetry (PIV) and fish behaviour and remote monitoring. Fieldwork will involve measurements of velocity and solute transport studies to quantify the magnitude of transverse and vertical velocity shear both in the near-pass reach and at a reach beyond the influence of the fish pass. This will take place at suitable sites such as Shrewsbury Weir (River Severn) and Flatford Mill (River Stour). The student will be an early career researcher in the Cardiff Water Research Institute (http://www.cardiff.ac.uk/water-research-institute) and a full member of both the HRC and CRIPES research centres in Engineering and Biosciences respectively (this has worked well for our previous joint PhD students), taking part in both seminar and social events.

Candidates should hold or expect to gain a first class degree or a good 2.1 and/or an appropriate Master’s level qualification (or their equivalent).

Applicants whose first language is not English will be required to demonstrate proficiency in the English language (IELTS 6.5 or equivalent)