Background:Project Background * Work Statement * Relevance Study Area Methodology:Past Studies Data Preparation *? Actual Data Adjustments * Modeling Procedure *? Models:Hydrology Model Lake Thermodynamic Model Water Balance and Routing * Hypsometric Relations and Outflow Equations * Validation:Interdependent Lakes: Base Case vs. Historical * NBS, Levels, & Channel Flows for whole system * * * Terminal Lakes:Split System & Replace St. Clair Equation * Consider removal of present-day diversions independent lakes NBS only (upstream lakes terminal) * NBS climate summary * interdependent lakes: Outflow climate summary * Lake Level summary * * Outline

Background Great Lakes in terminal state about 9000 years ago Hypothesize climate caused this Understand extremes of climate closing Great Lakes NSF proposal with 13 others funded late last year

Background Great Lakes in terminal state about 9000 years ago Hypothesize climate caused this Understand extremes of climate closing Great Lakes NSF proposal with 13 others funded late last year Work -- Simulate Great Lakes hydrology under various climates Use GLERL’s AHPS includes basin hydrology, overlake precipitation, lake thermodynamics, channel routing used in climate change impact studies for EPA, IJC, NOAA, & IJC Adjust lake & connecting channel conditions outlets with “natural” outflow-elevation relationships and connecting channels remove French River watershed use dynamic areas in evaporation remove existing diversions & consumptions Use similar methodology here propose climate characteristics compatible with geologic evidence or GCM simulations modify meteorological record to reflect proposed climate changes simulate resulting hydrology & compare to base case Build WWW interface of project results for other researchers & public

Work (continued) Model entire interdependent system (Georgian Bay draining into St. Clair) Model two systems independently Lakes Superior, Michigan, Huron, and Georgian Bay (used to drain to Hudson Bay) Lakes St. Clair, Erie, and Ontario (no inflow from above) Look at steady-state closed lake Steady-state (repeat adjusted meteorological record with initial conditions = ending) Sufficient to use zero outflow and look at climates giving levels below sill a) Superior terminal? b) Michigan-Huron-Georgian Bay terminal, given Superior terminal? c) Erie terminal? d) Ontario terminal, given Erie terminal? Relax constraint of upstream terminal lakes.

Relevance Increase understanding of Great Lakes sensitivity to climate change Previously, lake changes attributed to isostatic rebound & shifts in outlet elevation New findings suggest climate shifts Understand climate change impacts today

Study Area

Great Lakes have tremendous water & heat storage capacities Early Great Lakes Climate Change Impact Studies used simple constant changes in air temperature or precipitation in water balances GCMs simulate current & 2xCO2 conditions GCMs used for transient increases of greenhouse gases EPA in 1984 used hydrology components of GCMs to assess water availability Recent Similar Great Lakes Climate Change Impact Studies GLERL-EPA 2xCO2 impacts (1989) GLERL-IJC 2xCO2 impacts (1992) US National Assessment in Great Lakes (1999) Transposed Climate impacts (1998) Past Studies IJC LOSLR Regulation study (2004)

Climate Data models use daily data 1948—1999 ~1800 stations for overland meteorology ~40 stations for overlake meteorology Thiessen-averaged over 121 subbasins & 7 lakes Changed Climate “base case” scenario apply ratios & differences to historical data Data Preparation use with models to calculate climate change scenario

Actual Data Adjustments P’ = P * R T’ = T + D

Arbitrary initial conditions used with 2-yr initialization simulation period Estimate “steady-state” conditions repeat 52-yr simulation with initial conditions equal to end values, until unchanging Simulate with models on adjusted data sets for all scenarios (including base case) 121 watersheds and 7 lakes Interpret differences between scenarios & base case as hydrology impacts Modeling Procedure

NBS Adjustment

Hypsometric Relations

Integrated System St. Mary’s River St. Clair River Detroit River Niagara River St. Lawrence River

NBS

Matching MHG Historical Water Balance For Superior: Q S = (E S – ) 1.5 For Mic-Hur-Geo:Q MHG = 185 (E MHG – ) 1.5

Negligible Diversions Great Lake DiversionAmountSuperiorMich-HurErieOntario (m3s-1)(cm) (1)(2)(3)(4)(5)(6) Ogoki-Long Lac Chicago Welland COMBINED

S 2 – S 1 = Inflow + NBS – Outflow NBS

Steady-State NBS As a Function of Climate

Steady-State Outflow As a Function of Climate

Steady-State Water Levels As a Function of Climate

Terminal Lake Climates: Superior, 4.7 T + P > 60;Michigan-Huron, 4.5 T + P > 63

Steady-State Outflows As a Function of Climate

Steady-State NBS As a Function of Climate

Steady-State Climate Range

Lower Great Lakes Without Upstream Inflows For St. Clair: Q C = (E C – ) 2 (E C – E E ) 0.5,E C > E E > = (E C – ) 2 (E C – ) 0.5,E C > > E E For Erie: Q E = (E E – ) 1.5,E E > For Ontario: Q O = (E O – ) 1.5,E O >

Steady-State Water Levels As a Function of Climate Terminal Lake Climates: Erie, 4.7 T + P > 51;Ontario, 3.5 T + P > 71

Steady-State Outflows As a Function of Climate