GLSD Spring Update

Summer is almost upon us and the GLSD is gearing up for another busy summer. Our staff has been working on spring maintenance of our Conservancy properties, Aqweed harvesters, wastewater system, fish rearing facility, and projects on the County K and Sunnyside marshes.

Around the District, residents may have noticed that the lake level is up this spring. We had a mild winter, in which temps dipped below zero only 9 times since January. While most of the lake had ice cover for much of the winter, the full lake never froze completely over for an entire day. Only once (in 2001) since records have been kept, has the lake not frozen completely over for at least a few days. The next shortest frozen-over period was in 1957 & 1997 when the lake was frozen for only 3 days. Though the lake didn’t freeze completely, the large extent of ice cover did help limit evaporation from the lake. Coupled with late season snowfall in late February/March along with additional spring rain in April, the lake level has risen. The City of Green Lake has already begun managing the dam to retain as much water in the lake as the DNR will allow for the summer boating season.

While the rainfall & spring melt was relatively mild, we did have a few strong rainfall/runoff events which may have contributed to some early algae growth. We have had reports of robust amounts of filamentous algae seen around the lake. Please note that filamentous algae is solid and slightly stringy, as opposed to green algae or the potentially dangerous blue-green algae, which are more likely to look like pea soup or green paint in the water.

The GLSD & DNR released 27,661 lake trout into Big Green Lake from the District fish rearing facility in late April. The average fish released this year was 8.0” in length, which is the largest size we’ve ever produced. A sincere thank you to our DNR fisheries partners for their continued efforts on behalf of Green Lake. We’d also like to acknowledge the partners that help fund this program annually including Green Lake County, the City of Green Lake, the Green Lake Association, and several local fishing guides. An additional thank you to the GLSD’s own Stuart Marks and Dallas Lewallen who, for 6 months, do the daily management of the lakers to get them ready to hit the lake.

The GLSD is seeing an increase in the number of agricultural best management projects (BMPs) requesting grant funding in the watershed. A big thank you to the Green Lake County Land Conservation Department and our own Hannah Niewoehner, Watershed Coordinator, for their efforts to get these projects on the landscape. The increase in cover crops, as well as structural BMPs like sediment retention basins, will directly translate to phosphorus saved from entering Green Lake. While we still have a long way to go, this uptick in projects shows we’re on the right path to better water quality in Green Lake.

In the past 5 years, we’ve consistently seen reduced numbers of carp in both the lake and the adjacent shallow-water wetland areas. Carp are bottom feeders; they stir & resuspend phosphorus-laden sediments and they can decimate aquatic plant communities which further limits root systems holding sediments in place. Fewer carp equates to better water quality and a healthier ecosystem for the lake. Spring harvest numbers peaked in 2017 when a total of 170,500 lbs of carp were removed from the lake and the County K marsh. Last year the commercial harvester hired by the District and jointly funded by the GLA, was only able to net 5,400 lbs of carp in total. Carp harvest numbers
are expected to remain low this spring.

GLSD staff have been preparing for the summer aquatic plant harvesting season. Known as our Aqweed program, it is popular with many residents around Green Lake. However, it’s important to remember two critical points; 1) the GLSD operates the program under a strict DNR permit, and 2) aquatic plants form the foundation of a healthy and flourishing lake ecosystem. The cutting or removal of them should only be done when absolutely necessary. The DNR reminds us that aquatic plants are a lake’s own filtering system, helping to clarify the water by absorbing nutrients like phosphorus and nitrogen that could stimulate algal blooms. Plant beds stabilize soft lake and river bottoms and reduce shoreline erosion by reducing the effect of waves and current. Additionally, aquatic plants provide important reproductive, food, and cover habitat for fish, invertebrates and wildlife. These points are why the DNR does not allow the GLSD to operate our harvesters in very shallow water where we might damage the lakebed or stir up soft sediments. To maintain a healthy lake, we must maintain healthy native aquatic plant communities.

In most instances, control of native aquatic plants is discouraged or should be limited to high use recreational areas that are next to piers and docks or within navigational channels. The DNR monitors the management of aquatic plants in lakes throughout WI. They have been known to act against landowners/lake groups for improper removal of aquatic plants. If you have dense stands of aquatic plants around your pier, please contact our office to get on our harvesting list. Each time the harvester crew passes your property as they circle the lake, they will assess, and
if needed, cut aquatic plants in your shoreland area.