Rajib Kamal’s research while affiliated with University of Alberta and other places

Fish exposed to supersaturated total dissolved gas (TDG) levels can develop gas bubble trauma (GBT) which can lead to sublethal effects or mortality. Access to refugia in areas of high TDG that allows for hydrostatic (depth) compensation can mitigate exposure risk and GBT occurrence. The goals for this study were to examine resident fish habitat and depth use and assess exposure risk to elevated TDG levels related to hydropower operations in the Columbia-Kootenay system in British Columbia. Modeling was used to predict TDG levels for three operational cases (low, medium, and high spill rates). Acoustic telemetry was used to track rainbow trout Oncorhynchus mykiss (RT) and mountain whitefish Prosopium williamsoni (MW) reach and depth residency. Telemetry results did not differ among operational scenarios and aligned with known biological/life history characteristics for fluvial or fluvial-adfluvial species. Within-species MW reach residency appeared to be reflective of seasonal habitat selection for spawning, foraging, and refuge movements. Within-species RT reach residency appeared to follow habitat association patterns reflective of RT ecology. A risk assessment revealed that RT had a significantly higher TDG exposure risk relative to MW, but sufficient depth refugia habitat was available to mitigate exposure risk and GBT occurrence in both species. The results suggested that TDG exposure risk and actual risk depend on the interplay between species-specific ecology and TDG patterns generated by hydropower facilities. The ecological and TDG patterns in this study suggested that system- and species-specific studies will be required to generate detailed TDG exposure predictions for management decision-making.

Spill operations of hydropower facilities can generate supersaturated total dissolved gases (TDGs) that can negatively impact fish residing in downstream habitats by causing gas bubble disease and mortality. Assessment of such impact and management of TDG can be challenging, particularly in river systems with multiple dams, because this requires investigation of complex physical processes related to gas transfer and dissolved gas generation in spillways as well as its transport, mixing, and dissipation in the riverine environment. In this study, an integrated analytical platform was developed to model system-wide total dissolved gas levels during spill events. To test its functionality, TDG monitoring data from the lower Columbia River hydropower system was evaluated for different operational conditions. The system includes contributions from the dams on two other regulated tributaries. In addition to facility-specific estimates of TDG production, the system model provided TDG distribution in the river system, which provides rapid and accurate estimations for impact assessment or mit-igation. A ranking process was developed to address cumulative TDG risk for multifacility spill operations. This involved estimation of risk scores considering severity of supersaturation level, river depth compensation, and exposure duration for a given spill event, and grouping the scores into four risk categories defined as none, low, moderate, and high. This resulted in a risk assessment framework that identifies the potential risk zones and the degree and extent of fish habitat impacted for the combined facility operations in a complex river system. This framework can be used as a tool to help inform water management decisions for regulatory compliance and environmental performance, and provide a strategic assessment of the relative need for mitigation action.

In regulated rivers downstream of hydropower facilities, understanding how supersaturated total dissolved gases (TDGs) are distributed and dissipated is crucial, as they can negatively impact the aquatic environment. The objective of this study was to quantify the rate of dissipation of supersaturated TDG in the regulated Columbia and Kootenay Rivers and to evaluate whether it can be predicted by surface reaeration theories. Detailed measurements of TDG and river hydraulics were collected during two individual spill events conducted at the Hugh L. Keenleyside Dam (HLK) on the Columbia River and the Brilliant Dam on the Kootenay River. To estimate the dissipation rate, an analytical approach was used that incorporated transverse mixing between the spill and generation flow as well as tributary inflow. For four different gate operations at the HLK Dam, the average rate in the two hydraulically different reaches upstream and downstream of Kootenay River confluence was 0.004 and 0.021 h −1 , respectively. In the downstream reach, the rate was 0.038 h −1 during the spill operation at the Brilliant Dam. These rates were about 1.5-3 times higher than the surface transfer predicted by some well known reaeration models. Some potential causes of these higher rates were discussed, particularly the large variation in the downstream reach. Because of limited data availability, a conceptual argument based on gas transfer theories was presented, which indicated that the dissipation rates were likely enhanced by bubble-mediated transfer caused by liquid phase supersaturation.

Assessment of the dissipation of total dissolved gases (TDGs) is important in the downstream of hydropower facilities which often encounter TDG supersaturation. An analysis of the two consecutive spill events at the Peace River hydropower system, which includes the Bennett Dam and the Peace Canyon Dam, showed that the percent saturation of TDG and dissolved oxygen (DO) varied with spill rates, pre and post-spill conditions. The decay of TDG was comparatively slower than DO and the rates decreased with the drop of spill flows. For spill of 1,160 m³/s at the Peace Canyon Dam, the decay rate for TDG at the dam tailrace and at a distance 7 km downstream was found to be 0.005 and 0.0014 hr⁻¹, respectively. A conceptual computational fluid dynamics model of the reservoir indicated that density driven currents could affect the TDG dissipation.