During the last five weeks we have completed three weeks of harvesting on Devil's Lake. We wish to thank all of you who made donations to make this learning experience possible. If you have committed to a donation and wish to complete it follow this link.
The main purpose of this project was to gain on lake experience to be used in planning of future harvesting activities and hopefully provide a little relief to the current situation. In the near term harvesting will be part of Devils Lake Water Improvement District's (DLWID) three prong approach to vegetation management. The plan also includes application of herbicides and restocking sterile grass carp in Devils Lake. Here's a summary of what we've learned in the harvesting project.
During our 3 weeks of harvesting we removed 41.5 tons of elodea from the lake. That's 83,000 lbs!
Massive amounts of elodea suddenly appeared in Devils Lake between 2021 and 2022; a plant that was virtually non-existent in the lake two years earlier. To better understand the current situation the Devils Lake Neighborhood Association (DLNA) has funded an engineering survey of the weeds in the lake to document the physical weed coverage of the lake. This survey will provide the DLWID with information that should help the establish the extent of the weeds within the lake and the volume of weeds in the lake. This information will be useful to the DLWID and the ODFW in their discussion as to the appropriate number of sterile carp that hopefully will be approved for re-introduction into the lake at a future date.
Expectations Exceeded Reality
Our harvesting efforts resulted in a tremendous amount of material being removed from the lake. Depending on where you are on the lake the harvesting results vary. The weeds were so thick on the West end we spent a full week just trying to clear a path in front of the docs on the South shore. Because of our prevailing winds within a week more plant material floated across the lake through our clearing and stacked up against the South shore. On the North shore the harvester fared better.
When operating the harvester collects 90% of what it grabs. In the days that follow, bits of elodea that remained in the harvested area eventually break off and float with the wind. This material floats away from the North shore heading across the lake to the South. This phenomenon would continue for a couple of days after the harvester passed.
We had some success in creating channels by removing the first four feet of elodea making the areas somewhat passable by a boat. Unfortunately as the weeks progressed materials continued to drift South overwhelming the recently created channel on the South shore. The North shore channel seemed to remain somewhat intact.
Effort Frustrated by Elodea’s Life Cycle
Our project dates were limited given that we were well into the season when we found an available lake harvester. Our harvesting project completed about the same time that elodea begins its fall shedding. So by mid-August we began to see large floating mats of elodea on the lake. These are not remnants of the harvesting but rather part of the natural life cycle of elodea. Each year the plants shed large sections into the water column in preparation for a second growing season in the fall. These floating mats are a key part of the plant's reproductive strategy, floating off, eventually sinking to the bottom and root in a new location.
If you live on the South shore you’re absolutely overwhelmed by large tangled floating islands of weeds. Some are so dense that you will see ducks hitching a ride. Currently, homeowners on the South shores can clear their shoreline one day only to return to see thick dense weeds solid from bottom to surface within days. This is a huge problem that requires a solution.
Timing May Be Everything
As a community I think we were all surprised, perhaps shocked when we looked in the water this spring. Elodea was everywhere! Due to the relative lack of weeds in the preceding years there were no plans in May to have a harvester arrive at Devils Lake. That's when DLNA attempted to find a harvester and schedule some time on the lake. Initially we received a one week commitment. We were able to extend that commitment to 3 weeks.
Upon initial review it appears the best approach to harvesting in the future would be to begin a few weeks early in May to knock down a channel around the perimeter of the lake. Then return in late August to remove the floating mats of weeds that appear when the plants are sheading.
It's important to remember that the primary reason for using a harvester as well as herbicide is to reduce the volume of weeds in the lake. We want to give our future grass carp, if approved, a chance to have an impact earlier in their life cycle. This revised schedule should maximize the volume of material that could be removed and hopefully accelerate the lake’s recovery.
A Different Model
It appears that for at least the next 5 years harvesting activities will be a part of our lake. Ongoing harvesting will likely be done under contract to the Devils Lake Water Improvement District. We suggest the District fund the spring and fall harvesting projects. Perhaps during the interceding time individuals could independently contract with a harvester willing to come to the lake to work their individual properties.
Removal and Disposal
One of the biggest challenges in harvesting Devils Lake is setting up dump sites and removing the weeds from the site. This season we relied heavily on the generosity and expertise of North Lincoln Sanitary Service who helped stage drop boxes and backhoes in various locations as the harvesting progressed. We were able to use some public access points such as the boat ramps and a few homeowners gave us access to their lakefront. Some sites worked better than others. We learned drop boxes work but dump trailers may be a better solution as they're more readily accessible to the shoreline. We also need to find better methods of pulling the weeds out of the lake and putting them in the trailer. The 41 tons of material was hauled to North Lincoln Sanitary Service where it was laid out to dry. It was then gathered up and trucked out for composting. Our activities at shoreline dump sites made a bit of a mess and many of you volunteered to clean up these sites at the end of each day. Thank you all for your assistance.
A Learning Experience
Again we wish to thank all who participated in this project. It provided us with valuable information. The information we learned will be incorporated in the Devils Lake Carp Management Plan which will be a requirement of any permit granted by the Oregon Department of Fish and Wildlife. Next year ongoing harvesting activities will benefit from the knowledge gained.