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Lake Ontario Lake Scenarios

Lake Ontario 

Historic Summary

  • Long term (past 100 years) water levels have stayed fairly constant throughout time with stronger inter-decadal and decadal variability
  • Signature of major droughts is observed (lake levels declined) in the record.  For example, the Northeast experienced drought conditions in the early 1930's and mid 1960's as precipitation amounts were much below normal, and this corresponds to times with the lowest recorded lake levels.
  • Levels have oscillated closer to the long-term average in the last 50 years compared to longer periods of lower levels (1930's) followed by periods of higher levels (1940/50's)
  • Lake temperatures have been increasing over past 100 years - on average, increases have been about 5F

The plot below shows the long-term record of Lake Ontario lake levels with lake-wide monthly averages (blue dots) compared to the 1918-present period average.

Future Lake Level Projections

Lake levels are determined by the difference in the amount of water going into and out of the lake, which seems simple but in actuality is very difficult to quantify let alone model for the future.  Here is a more detailed draft explanation of the [Freelinking: node title "Role of Lake Ice and Evaporation in Lake Levels" does not exist].  The best available science to date conveys uncertainty in whether lake levels will increase, decrease, or stay the same, so planners should prepare for periods of high and low lake levels.  Lake level modeling efforts suggest the range of future lake levels will generally be within historic levels (see figure below), so planners can use past experiences of especially high and low periods to plan for the future. 

Lake Ontario Scenarios

Since lake level projections do not provide a clear picture of the future, developing plausible scenarios of future lake levels may help planners think through various responses to high or low levels.  Next, we provide two scenarios to consider that incorporate future climate information and human responses:

Scenario 1: Springtime Warming, Summer Drought 

This scenario is based partially on a true sequence of events that occurred in Lake Superior over the 2009/10 period, and it is plausible that these types of events will occur more frequently in the future.

  • Lake Ontario lake ice is substantially decreased during winter
  • Springtime air temperatures warm leading to earlier than normal ice-free lake
  • Lake water temperatures warm more quickly, which leads to an early start to the Evaporation Season resulting in greater than normal water losses
  • Sustained summertime drought is experienced in the Northeast
  • This type of event, especially when coupled with other lake level stressors (i.e., increased consumptive use, less precipitation, etc), results in a period of low lake levels

Scenario 2: Winter Warming, Strong Winter Precipitation Events

This scenario is based on projections that indicate warming, especially during winter, and an increase in extreme precipitation events.

  • Lake Ontario lake temperatures warm enough to prevent ice from forming during winter
  • The gradient between air and water temperatures is small enough that evaporation rates remain low during winter even though the lake is ice-free
  • There is an increase in extreme wintertime rain events that causes greater runoff into the lake, especially since it is not capped with ice
  • Lake levels rise in a flashy fashion in response