Date of Award

2026

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Environmental Engineering (PhD)

Administrative Home Department

Department of Civil, Environmental, and Geospatial Engineering

Advisor 1

David W. Watkins

Committee Member 1

Veronica Webster

Committee Member 2

Ben Kopec

Committee Member 3

Lauren Fry

Abstract

A number of studies have found that global snow cover is generally decreasing, but a closer examination at regional scales shows greater complexity. In the Great Lakes basin, contrasting trends have been identified. While snow cover is generally decreasing basinwide, leeward (downwind) regions have experienced increases in snowfall and snow cover. Changes in snow dynamics are also associated with shifts in runoff timing and volume due to earlier snowmelt and changing precipitation patterns. Streamflow analyses at gauges across the Great Lakes basin indicate trends toward earlier peak runoff and longer runoff periods, although these patterns vary among watersheds and lake basins. With warmer temperatures, the occurrence and characteristics of snow droughts and rain-on-snow events are also changing. Together, these changes highlight the need to better understand the spatial and temporal variability of snow and its climatic controls across the Great Lakes basin.

The first part of this research addresses changing snow dynamics in the Great Lakes basin by analyzing spatial and temporal patterns in snow water equivalent (SWE) using multiple snow datasets available for the region. Traditional snow metrics, including snow season onset, snow season end, snow cover duration, and maximum SWE, are evaluated together with Snow Water Storage (SWS), a metric that integrates the amount and duration of snow stored within a watershed. The analysis examines long-term trends in these metrics as well as changes in their interannual and decadal variability. The results characterize the spatial heterogeneity of snow change across the Great Lakes basin and identify areas where the magnitude, timing, duration, and variability of seasonal snow storage are changing.

The second part of this research builds upon the observed snow trends and variability by examining the climatic factors associated with changes in annual SWS. Annual SWS is related to lake surface temperature, lake ice cover, air temperature, and precipitation to evaluate the influence of regional hydroclimatic conditions on snow storage. The analysis also considers two large-scale climate indices, the North Atlantic Oscillation (NAO) and Niño 3.4, to examine whether broader atmospheric and oceanic variability contributes to year-to-year variations in Great Lakes snow conditions. These relationships are evaluated spatially across the basin to identify differences in the relative influence of local, lake-related, and large-scale climatic controls. The results provide insight into the factors associated with observed SWS variability and help explain why snow responses differ among watersheds across the Great Lakes basin.

Understanding how changing snow conditions contribute to hydrologic variability is important for effective water resource management in the Great Lakes, particularly for operational decisions that influence lake levels and outflows. One key application is the operation of the Compensating Works, which regulates flow from Lake Superior to the downstream Great Lakes through the St. Marys River. As runoff patterns into Lake Superior respond to changes in snow dynamics, precipitation, and evaporation, the robustness of the existing regulation framework under a wider range of hydroclimatic conditions becomes increasingly important. The final part of this research evaluates the performance of Plan 2012 using Net Basin Supply (NBS) scenarios within the Coordinated Great Lakes Regulation and Routing Model (CGLRRM). The scenarios represent a range of plausible hydroclimatic conditions and provide a basis for examining the performance and robustness of the existing regulation plan. The results identify potential sensitivities of the current regulation framework to changing hydrologic conditions and provide information that can support adaptive water management in the Great Lakes.

Together, the three components of this dissertation connect observed changes in snow hydrology, the climatic factors associated with those changes, and the potential implications of hydrologic change for water management. The research provides a basin-wide assessment of changing snow storage and variability, identifies regional and large-scale climatic controls on those changes, and examines the impacts of hydrologic variability on Great Lakes water regulation. These findings contribute to a more integrated understanding of changing snow hydrology and provide a basis for adaptive watershed and water level management under increasing hydroclimatic variability.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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