SM
Property Owners Association
HLPOA News

Lake Level Charts & Data

(Two new charts and data added 3/2/2017 – scroll to bottom of page.  Also, there are now older lake level graphs from 1978 to 2006 posted below the 2007 to Date lake level graphs)

Higgins Lake Level — Data Gathering:

Every fifteen minutes a submerged pressure gauge in Higgins Lake reads the pressure due to the height of water/ice above the gauge, converts this pressure to a lake level reading and sends the data to a United States Geologic Survey (USGS) office.  Click on the link below to visit the USGS website for Higgins Lake.

Lake level data for any period of time can be obtained by entering the desired dates in the date fields on the USGS website.  All of the lake level data used to create the series of charts in the list, below, came from the USGS website.

 

Lake Level Charts:

Listed below are links to charts of the USGS gauge height data for each calendar year, beginning in 2007.  Charts for future years will be added as the data becomes available.  The charts show the USGS lake gauge height (blue line), the legal lake levels (red line) and, beginning in June of 2008, the percent of the Cut River dam width open for flow (green line) per the Roscommon County Board of Commissioners data.

Note: the Cut River dam can never be 100% closed due to the unregulated 4.75 ft. wide opening in it mandated by the Dept. of Fisheries Div. of the DNR.  Therefore, 7% of the dam’s width is open for flow at all times.

Also shown below are two additional charts.  The first chart, “Seasonal Lake Levels vs. Legal (summer) Level – 1979 to Date”, covers the period from 1979 to date and shows the average amount (in inches) that the lake was either above or below the legal (summer) level as set by the Circuit Court in 1926.  For each year, two data points are shown: the blue dot represents the average daily lake level for the period from April 15th through October 31st and the red dot represents the average daily lake level during the prime recreational season of June 1st through September 30th.  On this chart is a straight red trend line that is a calculated mathematical linear regression done automatically by MS Excel on the raw data.  The purpose for having this line is to show the trend over time that the summer lake levels have been experiencing (decreasing). The second chart, “USGS Average Gauge Height – 1978 to Date”, shows the average yearly gauge height of the lake for the period from 1978 to date.  This chart also has a straight trend line, black in color, calculated by MS Excel, showing the trend in the yearly average lake levels over time (again, decreasing).  Both of these charts will be updated on a regular basis as newer data becomes available.

Lake Level Charts Prior to the 2007 Dam Reconstruction that Added Two Additional Flop Gates and the 4.75 ft. Wide Unregulated Opening.  1978 was the first year the USGS published lake level data for Higgins Lake, starting in October of that year:

Lake Level Attrition, Winter Drawdown and Ice-Over/Ice-Out Information  – 2007 to Date:

The link below contains a chart showing key lake level information for each year since the dam was reconstructed in 2007 with the addition of a second and third flop gate to facilitate drawing the level down when required.  This data includes: the date the dam was first opened in the fall to commence the winter drawdown, how much of the Court Ordered draw down was achieved, the Ice-Over and Ice-Out dates, etc.  There is quite a bit of data here and we beg the reader’s forgiveness for it being presented rotated out of position.  This was the only way to fit the data onto one page width for posting on our website.  It is suggested to print the page if the desire is to study it in detail.

Please review the footnotes at the bottom of the page.  They contain key information to help in understanding the information that is presented.  Also, because the lake gauge height and the Court Order(s) use both “inches” and “feet” when discussing the lake level and winter drawdown amounts, the column headings in this chart are defined in either inches or feet, wherever appropriate.  A detailed explanation of the data in this chart could be presented but it is likely not necessary to do so as careful scrutiny by the reader should be sufficient.

Notice in the earlier years the dam was opened to commence the 6 inch winter drawdown as early as Sept 5 (note: the Court Order for the 5 year trial 9 inch winter drawdown, starting 2009 and expiring for 2014, permitted it to begin as early as Sept 15).  In the summer of 2014, with the expiration of the trial 9 inch winter drawdown, the County Commissioners requested the Assistant Prosecutor’s interpretation of the language of the 1926 and 1982 Court Orders as to when the drawdown may begin.  He concluded the Orders state the County is to begin the drawdown on or about Nov 1st.  It’s interesting to note in the fall of 2014 and in each of the years that follow, the drawdown amount exceeded 6 inches, despite the later dam opening date.  In 2014 in particular, the lake level was only 0.84 inches below the Legal (summer) Level on Oct 29.  This has been the highest lake level immediately prior to the winter drawdown from 2007 to date, yet more than 6 inches of total drawdown was still accomplished by virtue of the reconstructed dam’s two additional flop gates.

It must be emphasized, as stated in the footnote, that for data of this type to be statistically valid and meaningful it requires a study period of more than just a few years – several decades is suggested.  The longer the study period, the more relevant and useful the data will become.  And more importantly, a consistent dam operating policy must be followed throughout the years.

 

Lake Level Decline During the Prime Summer Period:

It has been historically documented that the lake level drops during the mid to late summer months each year.  There are a variety of reasons for this: evaporation due to sun intensity, the amount of rainfall, variability of underground water in-flow as well as the 4.75 ft. unregulated opening in the Cut River Dam that is open for flow year-round.  The following link contains an analysis of the USGS Lake Level Data between June 15th and Sept 15th, the prime summer recreational period, for the years since the last major dam reconstruction in 2007, when the 4.75 ft. unregulated opening was incorporated in it.

The chart on the first page of the above link summarizes the time-weighted amount the lake level was either above or below the legal level for each year since 2007.  These time-weighted amounts are depicted by the green and red shaded areas on the graphs for each calendar year that follow the summary chart page.  By measuring these green and red areas (using a mechanical device known as a Compensating Polar Planimeter) the time-weighted amounts that the lake level is either above or below the legal level can be evaluated and compared.  This analysis shows that, on average since 2007, the time-weighted areas above the legal level averaged only 18%, while they are below the legal level an average of 82%.

Another important point in this analysis is the amount of time the dam is fully closed between June 15th and Sept 15th for each year, depicted by the green line.  With the exception of just a handful of days in many, but not all, of these years, the dam has remained closed – except for the 4.75 ft. unregulated opening.  In 2009, 2013 and 2016 the dam was never opened during the June 15th to Sept 15th  period.

In spite of the County’s best efforts to maintain the lake as close as possible to legal lake level, the 4.75 ft. unregulated opening plays a significant role in preventing this from happening.  The “bottom line” is that the dam as currently configured, without any means to restrict outflow through the unregulated 4.75 ft. opening, is not capable of maintaining the lake level in compliance with the existing Court Order.  Would a restrictor plate in the 4.75 ft. unregulated opening help to maintain the legal level from Ice Out to Nov 1st as required by the Court Order?  In the estimation of the Spicer Group, the Engineering firm that analyzed the existing dam configuration in 2010, a properly designed restrictor plate in the 4.75 ft. unregulated opening could reduce the amount the lake level drops in the late summer/fall by as much as 2 inches.  When an inch or so of water can make the difference in getting one’s boat off the hoist, a 2 inch improvement is more than significant.