utilization of hydrodynamic modeling in predicting water quality and brook trout habitat: reclamation of a mine impacted boreal shield lake
abstract
mining operations in ontario are subject to regulatory limits on effluent release into
surrounding waterbodies designed to preserve aquatic life. however, said guidelines may not
always be enough to prevent damage to the local ecosystem. this study examined cleaver lake,
ontario, an 18 m deep shield lake downstream of a copper/zinc mine active from 1987 – 1999.
mine activity resulted in increased levels of chemical constituents that created density induced
stratification prohibitive of seasonal lake turnover (meromixis). this condition persisted for
more than a decade after closure. resulting hypoxic conditions of deeper waters caused
extirpation of fish such as brook trout (salvelinus fontinalis) that require cool water and high
dissolved oxygen (do). the water quality and hydrodynamics of the effluent receiving lake were
modeled via ce-qual-w2 for the open water season of 2017. the model combined
bathymetrical data with inflow, outflow, and meteorological measurements, in-situ multiprobe
and data logger measurements of water quality characters like do and temperature, chemical
concentrations of potentially problematic metals (zinc = (81 ± 23) μg/l & copper = (3.7 ± 0.63)
μg/l) and density altering compounds from samples collected on site to make real-time
predictions of brook trout habitat. the model has accurately represented the recently observed
recovery from a meromictic state. the objectives of this project were to: (1) assess current
brook trout habitat with ce-qual-w2; (2a) predict potential future habitat based on what-if
scenarios such as a return to elevated levels of chemical effluent received via industry activity
and (2b) elevated air temperatures due to climate change. minimum survivable habitat
availability for brook trout was shown to be 69.97% in the unmodified model, reduced to
64.47% in the operational industry scenario, and 7.3% in the climate change scenario.