16.2
Decadal, Interannual, and Annual Variations of Water Levels on the Great Lakes
Jose A. Maliekal, SUNY, Brockport, NY
Millions of people who live within the shores of the Great Lakes, the most intensively used freshwater system on Earth, are accustomed to relatively narrow range of lake levels. Consequently, unexpected fluctuations in water levels disrupt human activities on and around the lakes. Among the factors contributing to this narrow range, the large surface area of the lakes and their relatively small inflow and outflow capacities are perhaps the two most important. In addition to the natural climate variability of the Great Lakes region, anthropogenic changes such as water diversions, navigational dredging, and infrastructures placed in connecting channels also influence lake water levels. The aforementioned anthropogenic activities are already greatly regulated; therefore, improved hydrological forecasting is essential for enhancing the efficiency of present and future water use and regulation. In order to improve hydrological forecasting, it is essential that we develop accurate conceptual models for describing the variability of lake levels. Since in each of the Great Lakes the inlet and outlet capacities are small compared to the volume of water, observed variability of lake levels provides an integrated picture of the climate change of the region.
To improve the present understanding of the variability of water levels in the Great Lakes, this study analyses time series of monthly mean water levels from various Great Lakes for the period from 1900 to 1999. First, time series are decomposed into decadal, interannual, and annual components with the help of a sequence of smoothing operations. A locally weighted regression procedure is used in almost all smoothing operations used in this study. Individual components are then used to highlight the nature of climate variability of the Great Lakes region during the study period. Initial results show that the decadal scale variability of water levels in the Great lakes matches closely with the long-term changes in regional precipitation. Cross spectrum analyses between the interannual component of the monthly mean lake levels and the time series of various climatic indices, such as the Southern Oscillation Index (SOI) and the North Atlantic Oscillation (NAO), and will be used to investigate how they influence the water level in each of the Great Lakes. Lastly, this study will also investigate whether or not the amplitude of the annual cycle is changing with time.
Session 16, Observed Variability and Change: Surface Part II (Parallel with Session 15 & Joint Session J1)
Thursday, 18 January 2001, 9:00 AM-11:44 AM
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