摘要：Hydropower plants can profoundly modify the natural morphology and
hydrology of rivers and can alter the functionality of habitats for fish living and
reproduction. In particular, hydropeaking leads to rapid and frequent changes of the
hydrodynamic conditions and it is crucial to ensure aquatic habitat quality is maintained as
much as possible during these periods. One present method to determine mitigation
measure (minimum and maximum flow, rate of change) is to perform hydraulic simulations
in 1D or 2D in the range of flow variation and to evaluate habitat quality for fish with the
microhabitat method. The hydraulic model calibration has to be conducted carefully since
the model has to reproduce precisely the hydraulic conditions from low to high flow rates
(up to several times the mean flow of the rivers). Within this range, the friction coefficient
can evolve greatly because at low flows the size of roughness elements become comparable
to the water depth.. This phenomenon is observed by performing the modelling and the
calibration at 2 stations on a river in French Pyrenees with different cross section shapes,
one with progressive overflowing of some banks with large blocks and the other one
without such phenomena. Thanks to field measurements of water levels at low and high
discharge, the calibration process has shown that the friction coefficient can be multiplied
by 2 as a function of the discharge. The paper proposes a methodology to evaluate the most
appropriate tool. As water depth is concerned, the 2D simulations (TELEMAC 2D)
provide similar results to those obtained with 1D (HEC-RAS) because flow remains
unidirectional. Then a sensitivity analysis is carried out to estimate the uncertainty on the
fish habitat outputs for a fish species (brown trout in the present study) resulting from
several widely used friction laws. These friction laws can lead to different conclusions
about habitat suitability depending on the calibrated coefficient. Finally, to perform relevant
habitat modelling, it is necessary to measure water levels at several discharges and to
describe accurately the spatial variability of roughness height.
其他摘要：Hydropower plants can profoundly modify the natural morphology and hydrology of rivers and can alter the functionality of habitats for fish living and reproduction. In particular, hydropeaking leads to rapid and frequent changes of the hydrodynamic conditions and it is crucial to ensure aquatic habitat quality is maintained as much as possible during these periods. One present method to determine mitigation measure (minimum and maximum flow, rate of change) is to perform hydraulic simulations in 1D or 2D in the range of flow variation and to evaluate habitat quality for fish with the microhabitat method. The hydraulic model calibration has to be conducted carefully since the model has to reproduce precisely the hydraulic conditions from low to high flow rates (up to several times the mean flow of the rivers). Within this range, the friction coefficient can evolve greatly because at low flows the size of roughness elements become comparable to the water depth.. This phenomenon is observed by performing the modelling and the calibration at 2 stations on a river in French Pyrenees with different cross section shapes, one with progressive overflowing of some banks with large blocks and the other one without such phenomena. Thanks to field measurements of water levels at low and high discharge, the calibration process has shown that the friction coefficient can be multiplied by 2 as a function of the discharge. The paper proposes a methodology to evaluate the most appropriate tool. As water depth is concerned, the 2D simulations (TELEMAC 2D) provide similar results to those obtained with 1D (HEC-RAS) because flow remains unidirectional. Then a sensitivity analysis is carried out to estimate the uncertainty on the fish habitat outputs for a fish species (brown trout in the present study) resulting from several widely used friction laws. These friction laws can lead to different conclusions about habitat suitability depending on the calibrated coefficient. Finally, to perform relevant habitat modelling, it is necessary to measure water levels at several discharges and to describe accurately the spatial variability of roughness height.
