LAKE HURON CLIMATOLOGY
Sustained Assessment of the Great Lakes
Lake Huron Overview
Located along the U.S. Canadian border, Lake Huron connects to Lake Huron through the St. Mary River, to Lake Michigan through the Straits of Mackinac, and to Lake Erie by way of Lake St. Clair. Lake Huron has the longest shoreline of any lake in the basin, due in part to Manitoulin Island. Lakes Michigan and Huron are treated as one unit for water levels as there is no physical separation between the lake bodies.
|Surface Area||Volume||Average Depth||Max Depth||Shoreline|
|59,565 sq. km||3,538 cu. km||59 m||229 m||3,830 km|
|(23,000 sq. mi)||(849 cu. mi)||(195 ft)||(750 ft)||(6,164 mi)|
Variability of water levels in Lake Huron is observed on many different time spans, including seasonal, monthly, annual, and decadal (Figure 1). Recent years have seen some of the most rapid fluctuations in the recorded history of Great Lakes water levels. Lake Huron had a sharp decline in water levels beginning in 1998. Following this decline, the lakes were characterized by an approximately 17 year span of warmer temperatures, low ice coverage, increased evaporation rates, and decreased runoff. Though this coincided with the 1998 El Niño, a causal relationship is not established. A rapid increase in Lake Huron water levels began in 2014, a year that coincided with a cold air outbreak, low temperatures, extensive ice cover, and high precipitation rates. These conditions continued through the end of the decade to reach record highs on several lakes in 2019.
Lake levels oscillate on annual cycles and multi-year periods of high and lows (Figure 2). The periods of sustained highs and lows are variable in length. The Great Lakes, including Lake Huron, have recently experienced a period of rising water levels, which follows a more than ten-year span of low levels. The past decade was the wettest on record and this record precipitation is the primary contributor to the recent rise in lake levels.
The variability of Lake Huron water levels is also observed on a decadal time scale (Figure 3). The current decade (2010s) of higher water levels occurred after a period of low lake levels (2000s).
Water levels fluctuate on an annual cycle, rising in the spring and summer due primarily to snowmelt runoff and low evaporation rates, and declining in the fall due to high evaporation rates from the temperature difference between the air (cold) and water (still warm from summer months). On average, the highest lake levels are observed between June and August (Figure 4).
The record lows on Lake Huron were set in the mid 1960s, with the exception of December and January records that were broken in 2012 and 2013 respectively (Table 1). The record highs on Lake Huron were set in the mid to late 1980s.
Table 1: Mean, maximum, and minimum water levels in Lake Huron (Source: Army Corps of Engineers)
Net Basin Supply:
Water levels for an individual lake are driven by the net basin supply (NBS), which depends on the sum of over-lake precipitation and basin-runoff minus over-lake evaporation, as well as how much water flows from one lake to the next. Human-caused diversions, into and out of the lake, are also part of the NBS, but are much smaller than precipitation, runoff, and evaporation (see Lake Levels Overview page for more information).
The variability of over-lake precipitation, evaporation, runoff, and total net basin supply can also be observed on a decadal time scale (Figures 9, 10, and 11). The most recent decade (2010s) had the most precipitation on record, which contributed to the increase in water levels that was seen throughout the Great Lakes, including Lake Huron. High runoff totals were also observed, primarily due to the high precipitation totals that have been recorded in the 2010s. NBS is the combination of precipitation, runoff, and evaporation, modeled by the equation: NBS = P + R – E (Figure 12).
There are multiple factors that lead to the differing levels of ice cover between the different lakes including depth, surface area, and latitude. The average depth of Lake Huron allows for lower capacity for heat storage than other deeper lakes, such as Lake Huron (Figure 13). However, the relatively large surface area allows for loss of stored heat, which is favorable for the formation of ice.