The objective of this task is to gather information on water levels from a standpoint of their geologic history, as compared to the recent history of recorded water levels. Evidence exists that water levels have been much higher and much lower than what has been experienced in the past 140 years since water levels have been recorded. The lakes may actually be at the bottom of a longer duration lower water cycle and could be destined for much higher levels in the next 140 years. Significant work has been performed in this area (i.e., Todd Thompson, Indiana Geological Survey and Curtis Larsen, U.S. Geological Survey and others) and will be reviewed for the LMPDS. Findings of this review will be used in the development of hydrologic scenarios and will be useful for enhancing the understanding of coastal processes.
Paleo-Lake Levels Workshop Held, April 1999
To begin work on this task, the LMPDS Study Team has contracted with the Great Lakes Environmental Research Lab (GLERL) to generate an executive level summary of previously published studies and current expert wisdom on the historic range of water levels for each of the Great Lakes over the current millennium (1000-2000). This summary will also compare and contrast recorded water levels on each of the lakes with a consensus opinion on the recent range of water levels over the last 1000 years. The summary will also include observations on the likelihood of climate change impacts on Great Lakes water that could occur over the next 50 years.
To this end, GLERL hosted a Paleo-Lake Levels Workshop in April of 1999 that brought together some of the foremost geologic, climatologic and hydraulic experts in the U.S. and Canada. Presentations were made of geologic and hydrologic research being conducted by these experts and significant discussions were held regarding the potential future range of levels on the Great Lakes.
HTML versions of the Introduction, Background and Key Findings of the workshop are presented here. The full Workshop Proceedings entitled, "Paleo Lake Levels - The Last Four-Thousand Years" can also be downloaded in .PDF format using the link below.
Paleo Lake Levels- The Last Four-Thousand Years
INTRODUCTION
Frank H. Quinn
Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, Mi 48105
quinn@glerl.noaa.gov
The Great Lakes are one of North America?s largest water resource systems with a basin area of about 770,000 km 2 , of which about one third is lake surface. It is one of the most intensively used freshwater systems in the world, serving multiple interests including navigation, hydropower, recreation, water supply, food supply, and riparian. The outflows from Lakes Superior and Ontario are regulated by regulatory works in the St. Marys and St. Lawrence Rivers, respectively. The remainder of the system is naturally regulated through the large surface areas and limited outflow capacity. Great Lakes water levels change slowly due to the large lake surface areas and constricted outlet channels, which integrate short-term climate fluctuations. Because of the relatively small range in lake levels, about 1.8 m, significant uses have become dependant upon small changes in water levels and outflows, resulting in system sensitivity to relatively small changes in climate variability and change.
The Great lakes water levels constitute one of the longest high quality hydrometeorological data sets in North America with master gage records beginning about 1860 with other sporadic records back to the early 1800?s. However, from a longer term perspective under the current system hydraulic regime, which has been in place for about 3000 years, we have only observed/measured about 5 percent of the time series. There is a highly likely probability that we could experience runs of high and low lake levels with extremes significantly higher than our present measurements would indicate. For example, few if any envisioned in the 1960?s that we would have a 30 year run of well-above-average high lake levels and set two record highs within 13 years. A longer term lake level perspective can only be obtained by examining paleo information from the geologic record, or in a more limited fashion, from stochastic hydrologic analysis based upon the historic record.
The workshop was convened to place the historical lake level measurements in a longer term perspective through a series of papers and discussion by highly qualified experts in the specialized field of Great Lakes paleo lake level reconstruction. This perspective will serve a broad range of uses from evaluation of potential Great Lakes shoreline damages to the development of more robust lake level regulation and water resource policy.
Paleo Lake Levels - The Last Four-Thousand Years
BACKGROUND
Joan Pope
Chief, Coastal Evaluation and Design Branch
Coastal and Hydraulics Laboratory
U.S. Army Engineer Research and Development Center
3903 Halls Ferry Rd.
Vicksburg, MS 39180
j.pope@cerc.wes.army.mil
Human perception of flooding and erosion hazards along the shores of the Great Lakes is often limited by the length of human memory and recorded past conditions. Yet, records of Great Lakes water level fluctuations cover only a little more than a century (1860 to the present). This is only a little more than 3 percent of the period that the Great Lakes system has existed with its present drainage system.
During the last 4 or 5 millennia, Great Lakes water levels have responded to geological, atmospheric, and anthro-pogenic changes. There have been subtle, yet progressive tectonic changes to the basin as the earth?s mantle and crust have adjusted to the disappearance of the massive Pleistocene continental glacier. These geotechnical changes have both tipped and warped the basins; modifying the relative elevation of the outfalls and levels of water impoundment in each lake. The Earth?s atmosphere exhibits poorly understood long and short period changes in the balance between polar and tropical air masses, the location of major pressure system lows and highs, and the jet stream. As the atmosphere evolves, meteorological cycles and trends materialize resulting in periods of greater or lesser precipitation for different regions of the earth. Within recorded time there have been seasonal, annual, and decadal alternating cycles of droughts and floods in the Great Lakes system resulting in periods of low and high water levels. In more recent times, man has modified the Great Lakes basin and drainage system through land use practices and modifications to the drainage system, including some changes to the capacity of lake inflows and outflows. Finally, there are the effects of atmospheric pollution and the unknown future associated with global warming.
Geological evidence developed by independent researchers studying different evidence in different locations throughout the Great Lakes suggest the presence of water level change trends associated with basin tectonics and longer period atmospherically-induced cycles than those captured in the recent record. Future stewardship of the Great Lakes system needs to look beyond the documented record in predicting future water level changes and potential extreme values.
In response to the 1993 International Joint Commission Great Lakes Levels Reference Study, the U.S. Army Corps of Engineers is developing a basin-scale Flooding and Erosion Evaluation System. This system includes a lake-by-lake relational database of geological, land use and hydraulic information; coastal recession, sediment and flood models; and computer-based linkages to analyze the erosion and damage consequences of changed water level and sediment supply scenarios. This interactive data base and analysis system provides those responsible for Great Lakes coastal zone planning, public policy, engineering actions, and operating water level control elements with a powerful regional management tool. The goal of this workshop is to develop rational future Great Lakes water level scenarios for use in the development and application of this regional management system.
Paleo Lake Levels- The Last Four-Thousand Years
SUMMARY OF FUTURE RESEARCH NEEDS AND KEY FINDINGS
Cynthia E. Sellinger
Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor Mi 48105
sellinger@glerl.noaa.gov
Future Research Needs
Paleo lake level research should be conducted on all Great Lakes to determine the physical limits and timing of past lake level fluctuations. It was agreed that there should be further research examining the relationship between long term climatic patterns and paleo-lake levels, the following research topics were suggested:
- Look at past air-mass movements with respect to environmental changes. Instead of focusing on the North-South shift, look at the East-West shift in Great Lakes climate patterns.
- Generate lake level responses to climate change.
- Develop global warming scenarios.
- Identify the climatic regime for each lake.
- Research submerged tree-stumps in the Straits of Mackinaw with respect to what they reveal about prehistoric precipitation patterns.
- Understand the ages of submerged reefs in Lake Superior.
- Determine the effects of deforestation on lake levels.
- Develop methods to accurately determine low lake levels.
Key Findings
- Evidence indicates that the range in historical water levels has been exceeded over the last 3000 years for both Lake Superior and Lakes Michigan-Huron (see Figure below).
- Paleo lake levels for Lakes Ontario and Erie are much harder to quantify but have probably varied around the historical range.
- The geologic record indicates runs of above average and below average lake levels with a quasi-periodic variation around 150 years. There is some belief that we may be moving from the high end of the range towards the low end of the range.
- The research into Great Lakes paleo water levels is very productive and useful for water resource studies. It should be continued with high priority given to Lakes Superior and Michigan-Huron.
- There may be a significant correlation between longer-term atmospheric circulation patterns and lake level fluctuations.
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