Session B4: Ethohydraulics in Turbulence: Fish Behaviour in Turning Pools

Abstract: Space restrictions often necessitate the incorporation of turning pools in the design of fishways. Several biological studies have identified potential problems fish have with turning pools, varying from disproportionate residence times, flow negotiating difficulties and even fish leaping out of the turning pool. Likewise, our research on fish passage times of a vertical slot fishway on the river Mosel in Germany, detected significant time lags in turning pools. A number of potential explanations have been stated in the literature including confusion associated with large vortices, turbulence and complex flows, flow characteristics exceeding the swimming abilities of the fish, or fish could be using such basins to rest. The actual activity within these turning basins remains unknown and represents an important knowledge gap. This paper presents the results of an HDX and sonar monitoring campaign, registering behaviour in a turning pool in a vertical slot fishway on the river Mosel in Germany, where increased passage times were recorded for several fish species in turning pools. Behavioural patterns like residence times, acc- and deceleration, resting and swimming tracks for both up- and downward migration are related to flow direction patterns described in a 3D hydraulic model. The results offer insights in the behavioural characteristics of migrating fish in turbulent basins, with direct implications on technical design features like rounded basins and additional baffle walls

Numerical Study of Three-Dimensional Surface Jets Emerging from a Fishway Entrance Slot

This article belongs to the Special Issue "Fish Passage at Hydropower Dams". Further information available online: https://www.mdpi.com/journal/water/special_issues/fish_passage_hydropower_da

Simulating seismic chimney structures as potential vertical migration pathways for CO2 in the Snøhvit area, SW Barents Sea: model challenges and outcomes

Carbon capture and storage (CCS) activities at the Snøhvit field, Barents Sea, will involve carrying out an analysis to determine which parameters affect the migration process of CO2 from the gas reservoir, to what degree they do so and how sensitive these parameters are to any changes. This analysis will aim to evaluate the effects of applying a broad but realistic range of reservoir, fault and gas chimney properties on potential CO2 leakage at various depths throughout the subsurface. Fluid flow might take place through parts of or the entire extent of the overburden. One of the aims of the analysis is assessing the potential of CO2 reaching the seabed. Using the Snøhvit gas reservoir and overburden in the Barents Sea, a series of geological models were built using seismic and well-log data. We then performed numerical simulations of CO2 migration in focused fluid flow structures. Identification of potential migration pathways and their extent, such as gas chimneys and faults, and their incorporation into these models and simulations will provide a realistic insight into the migration potential of CO2. In the simulations the CO2 is injected over a 20 year period at a rate of 0.7 Mt/year and migration is allowed to take place over a 2000 year time frame for domains of approximately 21 km2 for the caprock fault models, 24 km2 for the realistic gas chimney models and 35 km2 for the generic gas chimney models, in a layered sedimentary succession. The total mass of CO2 injected in the reservoir during the 20-year injection period is 14 Mt. There is a strong interaction between the various parameters but the parameter that had the most influence on the CO2 migration process was probably the permeability of the reservoirs, especially the average permeability (k). Also, for the faulted caprock scenarios, it should be noted that at near surface depths the permeability of 765 mD is already adequate for a good CO2 flow. At the chimney top level (600 m) however, a further increase in permeability has an additional effect on improving CO2 flow. Overall, considering the slow upward migration velocity of the plume, this geological setup can be regarded as a suitable storage site