Frank H. Quinn

Evaluation of Potential Impacts on Great Lakes Water Resources Based on Climate Scenarios of Two GCMs

Abstract The results of general circulation model predictions of the effects of climate change from the Canadian Centre for Climate Modeling and Analysis (model CGCM1) and the United Kingdom Meteorological Offices Hadley Centre (model HadCM2) have been used to derive potential impacts on the water resources of the Great Lakes basin. These impacts can influence the levels of the Great Lakes and the volumes of channel flow among them, thus affecting their value for interests such as riparians, shippers, recreational boaters, and natural ecosystems. On one hand, a hydrological modeling suite using input data from the CGCM1 predicts large drops in lake levels, up to a maximum of 1.38 m on Lakes Michigan and Huron by 2090. This is due to a combination of a decrease in precipitation and an increase in air temperature that leads to an increase in evaporation. On the other hand, using input from HadCM2, rises in lake levels are predicted, up to a maximum of 0.35 m on Lakes Michigan and Huron by 2090, due to increased precipitation and a reduced increase in air temperature. An interest satisfaction model shows sharp decreases in the satisfaction of the interests of commercial navigation, recreational boating, riparians, and hydropower due to lake level decreases. Most interest satisfaction scores are also reduced by lake level increases. Drastic reductions in ice cover also result from the temperature increases such that under the CGCM1 predictions, most of Lake Erie has 96% of its winters ice-free by 2090. Assessment is also made of impacts on the groundwater-dependent region of Lansing, Michigan.

Hydraulic Residence Times for the Laurentian Great Lakes

The Laurentian Great Lakes comprise one of the major water resources of North America. For many water quality studies the hydraulic residence times or replacement times of the Great Lakes serve as measures of how quickly water quality will change in response to changes in contaminant loadings. The residence time for a conservative substance represents the average time a conservative substance which remains dissolved in the water spends in a lake. The hydraulic residence times of conservative substances for the Great Lakes are relatively long ranging, from close to 200 years for Lake Superior to a little over 2 years for Lake Erie. A major reduction of 38 years was found in the residence time for Lake Michigan (62 years as compared with the 100 year value previously reported) due to the consideration of flow exchange between Lakes Michigan and Huron. This indicates that Lake Michigan may respond much faster to reductions in contaminant loadings than previously expected. Because of their low ratio of volume to outflow, only Lakes Erie and Ontario are affected by normal climatic variations of less than 20 years in duration. Extreme lake level conditions over the period of 2 to 8 years can also significantly affect the residence times of Lakes Erie and Ontario. Thus high levels in the early 1970s may have contributed to the improvement of water quality in Lake Erie. Existing diversions and potential global warming appear to have no significant effect on residence times.

Climate Change Impacts on the Hydrology of the Great Lakes-St. Lawrence System

A review of the current state of knowledge on climate change due to an ’enhanced greenhouse effect’ and the response of the climate and hydrologic systems to a changing atmosphere is provided. In particular, the survey presents historic trends in and the impacts of climate change on temperature, precipitation, evapotranspiration, runoff and Great Lakes levels. While much of the impacts research in the Great Lakes-St. Lawrence basin has used equilibrium 2 × CO2 scenarios, the transient scenarios for 2030 and 2050 from the Canadian Centre for Climate Modelling and Analysis and the United Kingdom Hadley Centre coupled atmosphere-ocean global circulation models are also described. If the significant declines in runoff and lakes levels suggested by climate change scenarios are realized, there could be serious supply-demand mismatches and water allocation issues. The issue of climate change reinforces the need for continued cooperative planning and management of the water resources of the Great Lakes-St. Lawrence basin.

HYDROCLIMATIC FACTORS OF THE RECENT RECORD DROP IN LAURENTIAN GREAT LAKES WATER LEVELS

Abstract An extreme low-water supply episode from 1997 to 2000 resulted in the largest 1-yr drop in Lakes Michigan–Huron and Lake Erie water levels (0.92 and 1.03 m, respectively) recorded since measurements began in the early 1800s. Lake Superior water levels were the lowest since 1925. Lakes Erie and Ontario also had relatively low levels. The episode was unusual, particularly when compared to the record-low water episode of the mid-1960s, in that the primary hydroclimatological driver was high air temperatures and not extremely low precipitation. The high air temperatures resulted in unusually high lake evaporation rates and decreased basin runoff. The drop in levels during this episode was compared to other 1–3-yr decreases throughout the period of record. A comparison of the 1997–2000 episode for Lakes Michigan–Huron with the 1960–64 episode, which led to record-low lake levels in 1964, shows that the various elements of the water balance have differing importance in the two episodes.

Secular Changes in Great Lakes Water Level Seasonal Cycles

Abstract The three primary scales of Great Lakes water level fluctuations are interannual, seasonal, and episodic. Of these three, the seasonal water level fluctuations have received relatively little attention. The Great Lakes water levels have a well defined seasonal cycle driven primarily by snowmelt in the spring and summer and lake evaporation in the fall and winter. The present average seasonal cycle ranges from 26 cm on Lake Superior to 38 cm on Lake Ontario. Great Lakes monthly water levels from 1860 to 2000 were used to assess changes in the seasonal cycle of each of the Great Lakes and Lake St. Clair over the past 140 years. Changes are found on all of the lakes during the period of record. They usually resulted in a decrease in seasonal range and a time shift in the months of seasonal maximum and minimum. The effects of lake regulation were found to be negligible in the case of Lake Superior and significant for Lake Ontario. The major changes on Lakes St. Clair and Erie are likely a result of changes in the connecting channels ice retardation rather than changes in seasonal hydrometeorology. Seasonal cycle regimes are delineated for each of the lakes and possible rationale for the changes discussed.

Hydrologic response model of the North American Great Lakes

Abstract A hydrologic response model of the unregulated portion of the North American Great Lakes is presented for use in water resource and research studies. The hydrologic response model is a water quantity model encompassing Lakes Michigan, Huron, St. Clair and Erie and their connecting channels. The input parameters include overwater precipitation, tributary runoff, evaporation and diversion rates for each lake in the system and ice retardation rates and discharge equations for the connecting channels. The model outputs are end-of-month and monthly mean water levels for each lake in the system and the monthly flow rates in the connecting channels. The equation set for the model is composed of the continuity equations for each lake in the system. Runge-Kutta and Newton-Raphson algorithms were investigated for use in the model solution as well as a second-order finite-difference technique designed by the author. The Newton-Raphson algorithm required approximately 40% less computer time than the other algorithms and was selected for inclusion in the solution. The model was calibrated by parameter optimization using an optimum gradient algorithm. The accuracy of the model as well as the sensitivity of the input parameters are analyzed and discussed.

Great Lakes Hydrology Under Transposed Climates

Historical climates, based on 43 years of daily data from areas south and southwest of the Great Lakes, were used to examine the hydrological response of the Great Lakes to warmer climates. The Great Lakes Environmental Research Laboratory used their conceptual models for simulating moisture storages in, and runoff from, the 121 watersheds draining into the Great Lakes, over-lake precipitation into each lake, and the heat storages in, and evaporation from, each lake. This transposition of actual climates incorporates natural changes in variability and timing within the existing climate; this is not true for General Circulation Model-generated corrections applied to existing historical data in many other impact studies. The transposed climates lead to higher and more variable over-land evapotranspiration and lower soil moisture and runoff with earlier runoff peaks since the snow pack is reduced up to 100%. Water temperatures increase and peak earlier. Heat resident in the deep lakes increases throughout the year. Buoyancy-driven water column turnover frequency drops and lake evaporation increases and spreads more throughout the annual cycle. The response of runoff to temperature and precipitation changes is coherent among the lakes and varies quasi-linearly over a wide range of temperature changes, some well beyond the range of current GCM predictions for doubled CO2 conditions.

Current Perspectives on the Lake Erie Water Balance

Abstract An analysis was conducted of the Lake Erie water balance for 1940–79, based upon the individual hydrologic components, including thermal expansion and consumptive use. Particular emphasis was given to the continuity of the system. Annual and monthly statistics are presented for each of the water balance components. While the Detroit River contributed 87 percent of the Lake Erie total water supply, the variability of the net basin supplies was also found to be of importance in explaining annual water level fluctuations. A major step function was found to occur in the annual water balance between 1958 and 1959, which illustrates the large discontinuities that can occur when calculating the net basin supplies from residuals rather than directly from precipitation, runoff, and evaporation. The annual water balance for 1959–79 was found to be well satisfied with an average annual residual of about 0.5 percent of the Detroit River or Niagara River flow. A distinct seasonality was noted in the mass continuity of the monthly water balance. Also on a seasonal basis, the change in storage due to thermal expansion was significant during the late spring and early fall months.

The History of Lake Superior Regulation: Implications for the Future

Abstract Lake Superior outflows have been regulated for the past 80 years. The last 15 years have encompassed both extremely high water supplies and lake levels and subsequent drastic declines in the levels of Lakes Superior and the lower lakes. The IJC is considering a study whose purpose would be the reexamination of the current Lake Superior regulation plan, which has been in use since 1990. In preparation for that discussion, several different aspects of past and potential future Lake Superior levels were analyzed. The stage-discharge equation representing natural flow conditions for the pre-1900 Lake Superior outlet was used to simulate “unregulated” Lake Superior outlet conditions, using actual water supplies. Net basin supplies developed for a climate change study were used to evaluate the potential effects of regulation on future levels. A 50,000 year set of stochastic net basin supplies, based upon the present climate, was also used to provide hypothetical upper and lower bounds. By comparing recorded Lake Superior levels to what might have happened in the absence of regulation and what may occur with future supplies, it is hoped that the development and/or evaluation of any future adjustments to the regulation criteria for Lake Superior might be aided.

A Reconstruction of Lake Michigan–Huron Water Levels Derived fromTree Ring Chronologies for the Period 1600–1961

ABSTRACT A dendrochronolgy of annual precipitation and air temperatures from six Great Lakes locations was used to reconstruct Lake Michigan-Huron water levels from 1600–1961 representing the present St. Clair River channel conditions and basin land cover. The reconstructions are based upon a multi-linear regression model relating multi-year annual precipitation and air temperature to annual water levels. An increased frequency of low lake levels was found to occur prior to the twentieth century, accompanied by a major extreme in water levels, greater than that experienced in the historical record, in the early 1600s. The comparison of simulated and measured water levels also indicates that the impact of some of the channel changes in the St. Clair River may be underestimated and that the major drop in lake level in the 1880s may be due to erosion as well as to decreased precipitation. The occurrence of extreme levels around 1640, in 1838, and in 1986 suggests a return interval of 150–190 years for extreme lake levels. The analysis also suggests that the variability of lake levels has greatly decreased over the last century when comparing tree-ring-derived level variability. Thus climatic periods used for the development of the current regulation plans may not be representative of the longer-term climate and lake levels.