Clatsop Plains Lakes Project
Portland State University
Center for Lakes and Reservoirs
PO Box 751
Portland OR 97207-0751
Since the middle 1900’s, invasive aquatic weeds have been a problem on many of the shallow, dunal lakes on the Oregon coast. The introduction of non-native aquatic plants such as fanwort (Cabomba caroliniana), Brazilian elodea (Egeria densa), fragrant water lily (Nymphaea odorata) and parrots feather (Myriophyllyum aquaticum), has caused problems with recreation on the lakes. Boating and water activities such as water skiing, swimming and fishing have become limited over time, as the weed coverage has increased. The weeds have also altered the morphology, chemistry and biology of the lakes. The natural macrophyte assemblage of the lakes has been altered, as the invasive weeds have come to dominate the lakes. With the increase in plant biomass, the nutrient cycling within the lakes has also been changed. The aquatic weeds have also caused the flow through many of the lakes to slow, so that particulates have begun to settle out and the lakes have begun to fill in, accelerating their natural ecological succession.
A view of Cullaby Creek and Triangle Lake
Purpose and Scope of Project
In 1994, three lakes, Cullaby, Smith and Sunset, on the north coast of Oregon were listed by the Oregon Department of Environmental Quality (ODEQ) on their 303(d) list for impaired water quality (Figure 1). All three were listed for invasive aquatic weeds. An influx of nutrients, while not the main cause of the excessive weed growth, has altered the water chemistry of the lakes posing additional considerations for management options of the aquatic weeds and lakes. The lake chemistry and relation to the macrophytes must be taken into consideration when management options are examined for the aquatic weeds and the lakes.
One of the many houses on Smith Lake, whose docks are surrounded by beds of fragrant water lily (Nymphaea odorata).
Portland State University is working with the ODEQ and local stakeholders, including the Skipanon and Necanicum Watershed Councils, Cullaby Lake Homeowners Association and the Smith Lake Improvement Inc., to create an integrated aquatic vegetation management plan for each of the three lakes. A plan is also being prepared for Coffenbury Lake, which is not currently invaded by invasive aquatic weeds. The plan for Coffenbury Lake will focus on the prevention of introduction of non-native aquatic plants. The management plans will detail the types, abundance and location of plants present, and management options for the control of these plants. The management plans will be developed using the 1999 Guide for Developing Integrated Aquatic Vegetation Management Plans in Oregon. Please note that this guide is out of date, as the regulations on the use of herbicides have changed in Oregon.
A view of fragrant water lilies (Nymphaea odorata) covering the surface of
As part of this management plan, the watershed of each lake basin was evaluated. The evaluation includes a site description and description of the geology, vegetative cover, wetlands, land types and use, hydrology and water quality of the lakes. It is important to characterize the lakes and their surrounding areas to examine how impacts to the watershed might also impact the lake. The problem of the weeds must be examined within the context of the entire watershed. Changing the macrophytes could have dramatic affects on the water chemistry of the lake, potentially leading to further problems. Any weed management must examine the potential interactions between the watershed and the lake.
The watershed assessment is currently being revised and a link to the document will be available in the future.
Fragrant water lilies on a plant sampling rake.
As part of the management plan and plant sampling, bathymetric maps will be created. This gives information on depth, volume and surface area of the lake. Although previous maps were created in the 1980’s, new technology makes the collection of data more efficient and accurate. More information on bathymetry is available on this website at http://www.clr.pdx.edu/projects/lakes/bathymetry.php
The maps are expected to be completed soon, and will be available on this website after that date.
Water Quality Sampling
Weeds and watershed activities contribute to water quality degradation in the lakes. Field sampling to characterize current condition of the lakes is required for development and evaluation of management activities. The data gathered by PSU may be used by DEQ in the future to develop a Total Maximum Daily Load (TMDL) for each of the lakes. The hydrology of the lakes is somewhat unique in that it is dominated by local groundwater; surface streams in the Clatsop Plains are rare because of the sand dune topography that characterizes the area. Sampling of inlets and outlets of each lake will occur, as will sampling of the local groundwater (see below).
Aquatic Plant Sampling
Identifying the different species of aquatic plants in the four lakes and their abundance is important to selecting the management options that will work best in each lake. We will be creating a list of plant species found in each lake, estimating frequency and abundance of each species, and mapping the distribution of plant species in each lake. The first sampling trip was completed in June; a second trip is planned in August. After the data has been collected, maps of plant locations and abundance throughout the lakes will be generated. Plant species list for each lake and associated tables and charts will be available soon.
Groundwater is the main source of water to these lakes. For this reason, PSU’s Geology Department is working to establish and understand the relationship between the lakes and the groundwater system. They will monitor and sample groundwater and lake levels to investigate flow directions and groundwater quality. Eric Nielsen is the graduate student working on the groundwater portion of the project.
Links and Resources
For additional information, check out some of these resources and links:
303(d) Fact Sheet at http://www.deq.state.or.us/wq/assessment/assessment.htm
Washington Department of Ecology: Aquatic Plants and Lakes http://www.ecy.wa.gov/programs/wq/links/plants.html
University of Florida’s Center for Aquatic and Invasive Plants http://aquat1.ifas.ufl.edu/
North Coast TMDL and Water Quality Info from DEQ
Final Report: Regional Lake Management Planning for TMDL Development [15MB pdf]
Prepared for: Oregon Department of Environmental Quality DEQ Contract Number:009-03
Edited by: Mark Sytsma, Center for Lakes and Reservoirs, Portland State University