By Dale Bacon
Birch Lake Water Quality
VLAWMO, the Vadnais Lake Area Water Management Organization, has released the 2017 Water Quality Report. There are 12 lakes within the VLAWMO watershed that are monitored for key water quality parameters include clarity, chlorophyll A, and key nutrients such as phosphorus and nitrogen. Jim Grisim, BLID board member and Board liaison to VLAWMO, volunteers to take biweekly samples on Birch Lake throughout the summer. Commercial laboratories analyze the samples.
VLAWMO staff analyzes the data to arrive at a Tropic State Index for each lake. The tropic state refers to the level of nutrients and plant growth in a lake. Oligotrophic refers to lakes with low levels of nutrients and plant growth. Eutrophic is the other end of the scale with excessive nutrients and plant levels. Eutrophic lakes are generally not useable for recreational use. Mesotrophic is in the middle of the scale, reflecting a balance between plant growth and recreational use. VLAWMO has chosen to simplify the index by using an A-F scale. Birch Lake is classified as Mesotrophic with a grade of B+
The board has requested that VLAWMO monitor the lake for chloride levels. The chloride level in lakes can be toxic to aquatic organisms. The chloride level is a result of runoff from road salt use. Current chloride levels show that the levels in Birch Lake are higher than other lakes in the watershed but still below the state standard.
Birch Lake continues to be one of the clearest and cleanest lakes in the VLAWMO watershed. Projects such as the phosphorus removal filter (see related story below) and lakeshore restoration help to ensure that the lake’s status is maintained for future generations.
VLAWMO has received a $97,000 grant from the Minnesota Board of Water and Soil Resources to install a phosphorus removal filter to treat storm water runoff entering Birch Lake. This project is a cooperative effort between VLAWMO, the City of White Bear Lake, and BLID. BLID has agreed to provide in-kind maintenance support.
The filter technology was developed at the University of Minnesota. The concept is fairly simple: the storm water runoff flows through the sand filter, which has been augmented with iron filings. As storm water runoff travels through the filter, soluble phosphorus in the runoff adsorbs to iron oxide present on the iron filings surface. A similar filter in Maplewood has achieved 90% removal of soluble phosphorus.
The filter will be located in the wetland area at the NE corner of 4th Street and Otter Lake Road. Drainage from this wetland flows into Birch Lake. Monitoring studies done on behalf of the BLID have shown that this is the largest source of phosphorus loading to the lake. The filter is estimated to remove about 8 lbs. of soluble phosphorus per year; this will help to stabilize the phosphorus levels in the lake.
The project is scheduled to begin this summer and should be completed by the end of the year.
Birch Lake Water Levels
2017 was a much drier year than 2016. According to the Minnesota State Climatology web site, total rainfall for 2017 was 30.80 inches. The total for 2016 was 42.71 inches. The mean rainfall for the period of record is 29.42 inches.
The water level in Birch Lake tracks rainfall amounts: 2016 lake levels hovered around the 920.00 feet msl (mean sea level) mark. Water flowed into Rotary Park for most of the year. 2017 started out with lake levels near 920.0 msl and gradually fell to the 919.5 msl. There was intermittent flow into Rotary Park during the second half of the year. Exact level data for parts of 2017 are unavailable due to gaps in the DNR database.
The historical lake level chart for Birch Lake shows that the level was fairly stable during the years 2014-2016. Limited data shows a drop off in 2017. The old timers have seen the lake go through cycles such as this. The worst of times have seen the lake 3 feet lower than it is today (see 2010 on the graph, as an example).
Photos of scenes to come, yes!!