November 2020 Update:
An October 2020 article in the Physics Today magazine highlighted the record high water levels currently being experienced across the Great Lakes region and the impacts that it has had on homeowners in lakefront communities. That article provides useful context for the report below and is available for download below or through the Physics Today website (https://doi.org/10.1063/PT.3.4589).
A PDF version of the report can be found here. This article is reproduced with the permission of the American Institute of Physics.
2021 Water Levels
Updated April 2021.
This is an update to the January 2021 report of high water levels in the Saugatuck and Douglas harbor area. Saugatuck and Douglas have continued to experience above-normal Kalamazoo Lake and River water levels through April 2021. However, the typical seasonal decline combined with a dry winter/early spring have led to current water levels being down more than a foot from April 2020 (~14 inches). Note that the present water level (approximately 580.5 ft. msl) is still significantly higher (approximately 22 inches) than the long term mean April elevation of Lake Michigan (approximately 578.74 ft. msl). The lake level forecast provided by the US Army Corps of Engineers (USACE) indicates that the water level over the next 6 months will likely rise slightly due to spring snowmelt and precipitation but remain below the record highs of last summer. Many stakeholders are again asking what is going on and will the Lake level significantly go down? We will try to address these questions with this discussion, but note the predictions on future lake level are educated guesses by NOAA and USACE scientists and engineers based on modeling Mother Nature.
First Point to Understand:
Kalamazoo Lake and Lake Michigan are hydrostatically connected! This means that as Lake Michigan rises, so does the Kalamazoo Lake and River. Kalamazoo Lake is what is referred to as a drowned river mouth.
Historical Lake Levels:
Let’s again look at the updated historical Lake Michigan water levels going back to the year 1918 (Figure 1). As discussed previously in the January 2021 report, Lakes Michigan and Huron are also hydrostatically connected by the Straits of Mackinac. The time history in Figure 1 shows at least six periods of high water and five low water level events, with a near record low occurring in 2013 (remember all the dredging concerns). Some modelers see a periodicity in high to low water levels of eight to fifteen years, but suffice to say the water level goes up and it goes down at least each decade. If we examine the length of high water events during the entire record we observe high water events as short as one year and as long as approximately eight years. The average duration of high water events is approximately four years. We are presently six years into this high water event and the plot shows we are trending downward. Good news.
Figure 2 shows in more detail the mean monthly water levels from 2020 and the start of 2021 relative to the historic maximum, minimum, and mean water levels. After water levels reached a record high in July-August 2020 (~582.4 ft. msl, 7.3 inches higher than the previous maximum), the water has steadily declined to a present value of approximately 580.5 ft. msl. This is down approximately 23 inches from the record highs of last summer, and 14 inches from the mean April 2020 levels, but still approximately 22 inches higher than the long term April mean.
The top of the seawall at East Shore Harbor Condos (ESHC) is at approximately 582 ft. msl, thus any Lake Michigan water level above 582 ft results in flooding. The 582 ft. msl is representative of the height of other seawalls in the areas, thus if there is flooding at ESHC flooding will be occurring in other parts of the harbor. The mean daily water level for Lake Michigan exceeded 582 ft every day from May 20, 2020 through early September. After that point, the average monthly water level has not exceeded 581.5 ft. msl, thus no flooding. The Lake Michigan water level gauge at Holland can be easily accessed (see NOAA's water level data for Holland, MI) to ascertain whether flooding of the shore is occurring. Just remember ~582 ft. msl or lower equals no flooding.
Present Lake Level and Near Term Trends (April 2021):
Presently Lake Michigan and thus Kalamazoo Lake are at 580.5 ft. msl which is approximately 42 inches above the low water datum (LWD) value. Water level is down approximately 14 inches from the mean April 2020 level (which was a record high for April) and 23 inches from the record high set in July 2020. However, the water level today is still approximately 22 inches higher than the long term average. The water level will rise again as spring continues due to river runoff and snow melt and peak in the July time frame.
Future Lake Levels:
The US Army Corps of Engineers, NOAA, and various Canadian government organizations all monitor the water level in the Great Lakes and make predictions as to future water levels. Some predictions look a few months into the future while others predict next year or five and ten years out. For this discussion we are presenting the USACE Great Lakes Water Level Outlook for a 12 month period starting from April 2021. Recall, three factors determine lake level; precipitation, evaporation, and runoff which is referred to as the Net Basin Supply (NBS).
Dry conditions from January-March 2021 led to a very low three month NBS. Figure 3 shows projected water levels based on a range of scenarios. The purple envelope represents the range of likely water levels based on 10 years that also experienced low January-March NBS similar to 2021. In this range of scenarios, the peak water level over the next year will be in July 2021 and still be 9 inches below the 582 ft msl flooding threshold. The much wider gray area represents the range of possible modeling scenarios based on historical data from 1900 to 2020.
The two solid lines represent water level projections if NBS and hydrologic conditions (i.e. air temperature, winds, precipitation) are similar to those observed in two other low January-March NBS years. The blue curve represents 1987-88 which, in addition to the low early season NBS, had below average ice cover across the Great Lakes (27%). This scenario would entail dry conditions continue through most of the year and result in little water level rise through summer 2021 and an April 2022 level approximately 15 inches below current levels. The green curve represents 2015-16 where the low March-June NBS was followed by a wetter than average late spring and early summer. In this scenario, the 2021 water levels would peak in July approximately 8 inches above current levels, with April 2022 levels within an inch of current levels.
The orange envelope represents a 6-month forecast range based on currently projected weather conditions, with the dashed orange line being the most probable forecast. This forecast would put the next six months close to the green (2015-16) curve, representing a seasonal water level rise, but one that should not result in much flooding.
The high water levels of 2020 created problems and large expenses for the harbor stakeholders. The big question that we do not have a reliable answer for is, when if ever will the water return to normal (i.e. is near average value). It really is mostly about the precipitation and evaporation. The average annual precipitation in the Michigan watershed basin is approximately 32 inches, with a high value of 40 inches occurring in 1985 and a low of 21.6 inches in the year 2016. Last year (2020) the annual precipitation in the Saugatuck area was 39.2 inches, near the high. However, despite the 2020 La Niña event, we had a dry winter, resulting in the continued reduction in water levels. The takeaways are:
- Kalamazoo Lake and Lake Michigan are hydrostatically connected, if Lake Michigan rises so does Kalamazoo Lake and River.
- Remember the number 582 ft msl. When the gauge at Holland reads 582 ft or higher we are going to get flooding.
- Storm surge and seiche events on Lake Michigan will still occur and result in local flooding due to the high water. In normal times we barely notice these occurrences.
- The future lake level is all about NBS, really it translates into rain and snow fall. Above average precipitation in the Great Lakes Basin spells trouble.
A PDF version of the report can be found here.