Water Quality

Water Quality
Water Quality - 5/6/2020
Water Quality
This is my favorite time of the year to be on Oswego Lake. Weather is starting to get sunny and the water warm enough to allow water activities without risk of cold shock when falling in. This, and the clear water brought on by an explosion of water fleas. Unfortunately the clear water brings with it filamentous algae growth in some areas, which you can read about in the Operations article.

Lakes this time of year experience what is called a "clear water phase" which, as the name implies, means water is much more transparent than in other times of the year. In Oswego Lake this is the period after sediment from winter storms has settled out but before the water warms enough for cyanobacteria and algae to become dominant. The primary factor in clearing the water is the water flea genus Daphnia (image above from here)

Daphnia are filter feeders that are an important food source for fish and aquatic insects. As filter feeders they ingest anything that can fit into their food groove, which of most benefit is green algae, but other things make it in there as well. Daphnia become most active at water temperature between 55 and 65 degrees and have a very high reproduction rate, producing a new clutch of eggs every three to four days of their two month lifespan. They will continue to thrive as long as there is enough food available and the water temperature is favorable. Eventually they eat most of what is small enough to be ingested and will die off in absence of additional food. This boom and bust cycle can repeat itself as long as the water is not too warm. Oswego Lake warms to around 80 degrees during summer, which is outside their thermal envelope so their populations are very limited.

Last year the clear water phase peaked around May 23rd with visibility of 22 feet of transparency. Currently we are up to 17 feet visibility and there are a lot of Daphnia in the water right now so I assume visibility will continue to increase. And since the water temperature is only 60 degrees they are still well within their thermal range to continue reproducing. 
Clear water will persist as long as the water is cool enough and we do not have a heavy rain event that moves a lot of sediment into the water. The good news is the Oregon Department of Agriculture weather modeling predicts summer weather closer to normal again this year. This should extend this clear phase and moderate the amount of cyanobacteria the lake generates during summer.

Watershed Council
The Oswego Lake Watershed Council has been advocating for watershed health and leading community members on restoration projects since its inception in 2010. The work they do to educate homeowners about living in a watershed, and leading volunteers in restoration projects helps Oswego Lake by restoring streamside habitat and bringing consciousness to actions that may harm the aquatic environment. The Council is 10 years old this year, the same year of the 50th anniversary of Earth Day. Stephanie Wagner, the current President of the Council penned a remembranceof Earth day that is worth reading. I would encourage you to visit the Watershed Council website to see how they have helped our community, and donate time and/or money to assist their cause.

As a founding board member of the council I am in charge of restoration at Park on South Shore just west of McVey. Previously this site was a National Guard base before the school developed the property in 2014. Lost Dog Creek traverses the property, and during the original property development decades ago (1940's likely) the creek was pushed north to make room for a training field. Currently it is channelized into a narrow, three foot wide stream that winds around the current ball field.

As a result of the creek much of northern property is protected as sensitive lands, making a lot of habitat available for restoration. Currently the property is dominated by invasive weeds like herb robertshiny geraniumItalian arumgarlic mustardJapanese knotweed, and English ivy. I visited the site last week and spent some time with Jack Halsey, the Council Coordinator pulling garlic mustard. Now is the time of year to remove this invasive plant because it has just flowered, but not yet cast seeds. We pulled and bagged the material, disposing it in the trash to keep seeds from spreading.

This work adds to three years of restoration work the Council has led in coordination with Park Academy. They have been a fantastic partner in our restoration efforts and have eagerly integrated the restoration activities into class curriculum. As we move forward the goal is to restore the rest of the property and work to de-channelize some of the creek so it does not scour and erode material from the during high flow. It is partnerships like these that make OLWC restoration efforts successful. There are several similar projects in the watershed, and as previously stated you can help by contacting the Council to provide volunteer time, in-kind or financial support for their efforts. 

Asian Giant Hornet
This week there was an article in the New York Times about the invasive Asian giant hornet that preys on our native honeybees. The article stated they have not been found in Oregon yet, but there is anecdotal evidence they have been seen in Portland. The Washington Dept of Agriculture has a set of instructions for building a trap for the hornet, and if you happen to see or capture one please contact the Oregon Department of Agriculture, as listed on the Oregon Invasive Species Council website. Our native honeybees are already suffering from habitat loss so they do not need an aggressive predator working against them.