Lake Levels

Lake Serene by M. FussellResidents and lake users are often interested in lake levels as changes can affect the recreational use of the lake. High lake levels can also flood shoreline property. While flooding can increase erosion and sediment entering the lake, it does not pose a substantial threat to the water quality. 
 
Lake levels naturally fluctuate and we expect variation to continue as the climate changes. Continue reading to learn why lake levels change, the County's monitoring data, and options for adaptation. 

Continuous Lake Level Data

Snohomish County has electronic lake level gages installed at nine area lakes. These gages take lake-level readings every hour. The data can be viewed and downloaded in our online water quality database for these lakes:

  • Cassidy (12/2014 - present)
  • Goodwin (04/2016 - present)
  • Martha South (1/2015 - present)
  • Serene (02/2013 - present)
  • Stevens (01/2008-12/2021)
  • Flowing (02/2021 - present)
  • Martha North (11/2020 - present)
  • Roesiger (03/2012 - present)
  • Shoecraft (04/2016 - present)

To view continuous lake level data:

  • Go to the online water quality database
  • Select “Hydrology”
  • Select the location on map or select from the station drop down menu
  • Click on “Open Channel Water Level” in the left side to view lake level data options
  • Select the data variation you want. “Published” is hourly data.
  • Select a date range on the right above the graph
  • Download data using the download icon on the top left of the graph

Volunteer Collected Lake Level Data

SoLOCSS staff plate to measure lake level at Lake Cassidy Opens in new windowme lakes within the county have lake levels being tracked through the Lake Observations by Citizen Scientists and Satellites (LOCSS) project. This NASA-funded project is to study why and how the volumes of lakes around the world change over time. They are also exploring what affects lake levels the most. The study compares lake-level data from community scientists with satellite imagery.  

Snohomish County partnered to install lake-level gages at nine local boat launches. Anyone visiting the lake can contribute to the project by reading the lake level from the gauge and texting it into the phone number on the sign. You can then view your data online at the links below! The Snohomish County lakes included in this global project include: 


Frequently Asked Questions

Why do lake levels change?

Lake levels will vary from season to season and from year to year. Most lakes in the county are not actively managed and have free-flowing outlets. Therefore the biggest factor that influences lake levels is precipitation. Other natural factors include evaporation, beaver activity, and groundwater levels, as well as human changes like debris in a culvert and increased development of impervious surfaces.


Lake levels are also influenced by long-term changes in climate. The Pacific Northwest is projected to have wetter winters and dryer summers. A 2017 SWM study showed that over a 25-year period there was a 25% increase in average annual rainfall amounts. Additionally, the style of rain storms are changing. Larger storms bring rain in a short amount of time. Rain doesn’t have time to sink into the ground which means more water runs over the ground and into the lake, causing lake levels to rise quickly. 


Who is responsible for managing lake levels?

Most lakes in Snohomish County have naturally flowing outlets and lake levels are not actively managed. Snohomish County does not have the authority to manage lake levels. However, Snohomish County is responsible for culverts that flow under county roads. Snohomish County will assist in clearing blockages of county-owned culverts. If your lake outlet flows under a county road and you believe the culvert is blocked, please contact Surface Water Management at 425-388-3464 or email surfacewater@snoco.org.  


Some lakes have weirs or dams and the lake level is controlled by these structures. These lakes have known outlet control structures. 


What can I or my community do to manage lake levels?

Outlet streams are often on private property. If a blockage occurs on a stream on private property, the landowner may choose (but is not required) to remove the blockage if all appropriate permits are obtained.  


Shoreline residents are also affected by lake levels and often interested in addressing issues. Therefore, lake-level issues are best handled through a group of lake area residents such as lake or homeowner association. Homeowner groups can help residents come together and make decisions on how a lake system should be monitored and managed if management is possible. Even with a lake association, there are limitations on what can be done to manage lake levels in most lake systems. Below are some options for lake area residents:


  • Help resolve blockages: Depending on the size of the lake and its outflow, manmade and natural debris can collect and block the lake causing water levels to rise. Communities can work together to remove the debris. If the outlet is on private property, the community will need to get permission from the landowner. Removal of manmade or floating debris requires a permit as well. Any work in streams and lakes to remove materials will need a permit from the Washington State Department of Fish and Wildlife. 
  • Working with Beavers: Beavers can influence lake levels when they construct dams on the streams that flow into or out of a lake. If beaver dams are constructed at the outlet and limit water leaving the lake, residents can install "beaver deceivers." These have tubes that allow the water to flow through the dam yet do not trigger the beavers to reconstruct the dam. This method is preferable to trapping or removing beavers as they often quickly move back in. Any work on beaver dams requires a permit from the Washington Department of Fish and Wildlife. Learn more about living with beavers.
  • Lake level adjudication: Property owners on a lake can come together and petition the court to adjudicate the level of the lake, which then requires the Department of Ecology to fix and regulate the lake level according to a lake-level management plan. Ecology would bill the lake residents for this work and subsequent maintenance. Some lakes have outflows that are too wide for mechanical structures to work effectively at regulating the water levels. This solution is primarily effective for lakes that regularly have too low of water levels rather than those that experience high water levels.
  • Adjust to changing water levels: Many of our lakes are likely to have higher winter wateShoreline planting at Panther Laker levels and lower summer levels as we experience changes in our climate. Residents can adjust to higher water levels by restoring native plant communities along their shoreline. Extra vegetation, adapted to wetter conditions can help reduce the negative impacts of high water, such as flooding and erosion. Re-configuring infrastructure like docks and septic fields also can reduce the potential damage from seasonal changes. Find out more about shoreline plantings including free assistance creating a planting plan and free shoreline native plants at www.lakewise.org. 
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