Analysis of nearly 120 years of Great Lakes water supply to identify changes in extreme events

Session: Large Lakes’ Response to Climate: Past, Present, and Future (3)

Lauren Fry, US Army Corps of Engineers - Detroit District, [email protected]
Deanna Apps, U.S. Army Corps of Engineers, [email protected]

Abstract

Recently, the Great Lakes have undergone a number of extreme events. After a decade-long period of low water levels culminating in record low levels on Lake Michigan-Huron in January of 2013, the lakes saw a record setting two-year rise, and currently the upper lakes are near record high water levels. On Lake Ontario, record high water levels were seen in the spring and early summer of 2017. This presentation will share results from a study investigating time series of residual Net Basin Supply (NBS), which represents the contribution to each lake excluding connecting channel flows. While various previous studies have assessed changes in components of NBS (e.g. precipitation, runoff, and evaporation) or meteorological drivers of NBS (e.g. temperature), changes in NBS are often not highlighted in previous studies.  The study aims to answer the following questions over time scales ranging from monthly to inter-annual: (1) has the frequency of extreme water supplies changed since 1900, (2) is the definition of “extreme” changing as it relates to water supply, and (3) how are changes in extremes at various timescales reflected in water levels?