Pomeroy, John W.Kevin Shook2023-10-252023-10-252012https://hdl.handle.net/10388/15174Analysis of the Lake Diefenbaker operation and hydrometeorological events of 2010-2011 suggests that minimum reservoir levels have been rising over time and were particularly high in the winter and spring of 2010-2011 resulting in a greater risk of high outflow events if predicted inflows were not accurate. Rules and policies for operating Gardiner Dam based on verified information and priority of operations to minimize cumulative risk were not in place to optimize dam operations after several mid winter events restricted outflows from the dam. Unfortunately inflows were underpredicted in 2011 due to underestimation of upstream snowpacks, inability to quantify ungauged inflows from prairie runoff, inadequate available information on upstream and local meteorological conditions, and reliance on statistical forecast procedures based on previous climate conditions. The impact of outflows on downstream areas was difficult to quantify because of an underestimation of outflows from the Coteau Creek hydroelectric station at Gardiner Dam and the lack of sufficient hydrometric stations downstream. Whilst water supply goals for the reservoir were met in the period, and downstream flood extent was cut in half; the acreage duration of flooding between Moon Lake and Saskatoon was not reduced by dam operation and the annual peak flow downstream on the Saskatchewan River was not reduced by dam operation. The overall evaluation of SWA operation of Lake Diefenbaker in light of the operational objectives understood at the time is that SWA forecasting staff did a superb job with the limited tools and resources, complex operating system and unspecified operating rules available to them.enAttribution-NonCommercial-NoDerivs 2.5 CanadaReservoirsDam operationsStreamflowLake Diefenbaker, SaskatchewanTechnical Report