Water levels in the Great Lakes–St. Lawrence system located in northeastern North America are critically important to the Canadian and U.S. economies. Water managers are concerned that this system, which is currently managed by control structures at the outlets of Lakes Superior and Ontario, is not able to cope with the highly uncertain impacts of climate change. In particular, the frequency of extreme water levels throughout the system might be substantially increased. This study provides an exploratory conceptual analysis to determine the extent that new control structures at the outlet of Lake Huron or Erie (or both) and corresponding excavation along the St. Clair or Niagara River (or both) might mitigate the risks posed by future extreme water supply scenarios. Multilake parametric rule curves were developed to regulate systems enabled with these new control structures as a whole. Multiple stochastic water supply sequences were adopted that represented different future extreme climate scenarios. A multiscenario, multireservoir (multilake), biobjective simulation-optimization methodology was developed to optimize the rule curve parameters in such a way that the risk of experiencing extreme water levels is robustly minimized and fairly distributed across the system. The biobjective setting was designed to embed the secondary objective function so that the cost of the new control structures and excavation generates trade-offs between the costs and the associated achievable risk reductions. The recently developed Pareto Archived Dynamically Dimensioned Search (PA-DDS) multiobjective optimization algorithm was enabled with the efficiency-increasing “deterministic model preemption” strategy and utilized to solve the optimization problem. Results demonstrate that although systemwide regulation with the new control structures could substantially reduce the risk (i.e., by 86% compared to the current or base level of regulation), it could not eliminate such events entirely and would cause adverse effects on the lower St. Lawrence River. Numerical results also suggest that implementing a single new control point at the outlet of Lake Huron would not be effective despite its high cost; however, a single new control point at the outlet of Lake Erie would be very effective, with considerably less associated cost.
Abstract A revised approach to the calculation of baseflow using the method originally proposed by the United Kingdom Institute of Hydrology is presented. The revisions resolve two aspects of the method that lead to less than optimal results; that is, the calculation of values of baseflow that exceed the corresponding values of streamflow and the dependence of the calculated values on the origin of the five-day segmentation of the input streamflow data. The approach is illustrated using streamflow monitoring information that is typical for areas of southern Ontario, Canada, where baseflow is primarily the result of groundwater discharge. Key words / Mots clefs: baseflowgroundwaterstreamflowécoulement de baseeaux souterrainesécoulement fluvial Additional informationNotes on contributorsAndrew R. Piggott andrew.piggott@ec.gc.ca
Nous presentons une approche amelioree du calcul de l'ecoulement de base, appuyee sur la methode proposee a l'origine par l'Institut d'Hydrologie du Royaume Uni (UKIH). Les ameliorations reglent deux problemes inherents a cette methode qui l'empechaient de donner des resultats optimum; en l'occurrence le calcul des valeurs de l'ecoulement de base qui sont superieures aux valeurs correspondantes de l'ecoulement fluvial et la dependance des valeurs calculees vis a vis de l'origine de la segmentation sur cinq jours des donnees d'entree d'ecoulement fluvial. Nous illustrons l'approche a l'aide de donnees observees de l'ecoulement fluvial, typiques de regions du sud de l'Ontario, au Canada, ou l'ecoulement de base resulte essentiellement de l'emergence d'eaux souterraines.
