Evaluate the value of the developed system by linking predicted reductions and ecological tolerance levels for supersaturation
There are significant knowledge gaps concerning the tolerance fish and invertebrate species have for air supersaturation. After model- and physical testing of the developed system to reduce total dissolved gas supersaturation (TDGS) downstream of the turbine (WP1) and establishment of a predictive model for estimating the reduction in TDGS, a link has to be established to ecological risk evaluation in different river systems.
The ecological risk induced by TDGS depends on
a) the tolerance of species and community
b) the extent of TDGS meaning both gas levels and habitat area affected.
Our modelling results are linked to the existing risk evaluation method for salmon juveniles in Norway. The tolerance level of other species is provided by cooperating with the SUPERSAT project. SUPERSAT explores the prevalence of TDGS in rivers and establish tolerance levels for important freshwater fishes and aquatic insects.
The existing degassing model25 for the Otra river can predict the dispersal of TDGS from Brokke hydro power plant and sources in similar rivers. The transport model for TDGS is improved by including both hydraulic and TDSG data for other rivers and hydro power plants, including SUPERSAT cases. Thus, effects on species and habitat area can be modelled by linking
a) our new model of change in TDGS at the source
b) hydraulic modelling (2D)
c) model of degassing in the river.
By developing and applying these models we can predict how effective our technical degassing solutions are in improving environmental conditions. The result will be presented as a cost-benefit analysis, including yearly costs and area of unaffected habitat gained.