EFFECTS OF RIVER FLOW FLUCTUATIONS ON GROUNDWATER DISCHARGE THROUGH BROOK TROUT, SALVELINUS-FONTINALIS, SPAWNING AND INCUBATION HABITATS

The effects of short-term fluctuations in river discharge simulating a hydroelectricity peaking regime on the hydrogeological environment of the brook trout's reproductive habitats were examined. Fluctuating river levels altered shallow (less-than-or-equal-to 2.5 m) groundwater pathways, chemistry, and flow potentials within the river bed at spawning and incubation sites. Rising river levels introduced river water into the bank where various degrees of mixing with groundwater occurred. Subsequent recessions of river levels increased the potentials for groundwater flow, particular in an offshore direction. The character of the river water - groundwater interaction appeared to be related to the hydrogeological nature of the river channel and adjacent catchment which varied among sites. The observations suggested hydroelectricity peaking regimes have potential negative impacts on brook trout reproduction.