Water Science: Bathymetry

This Spring VLAWMO is partnering with Ramsey Conservation District to get a better understanding of lakes on the outskirts of the watershed. As part of the 2017-2026 Comprehensive Water Plan, we’re starting the 10-year project cycle with a focus on the far-reaching lakes. As the years go by, our focus will follow the path of the water, leading to the destination, Vadnais Lake. The goal of course, is to improve the whole watershed!

Bathymetry is the process of mapping a lake (or ocean) bottom. These studies occur around the State and country to help understand how the body of water acts. Depth and shape are simple attributes of the lake that make a big difference in the lake’s ecology. For example, a Bathymetry study on Tamarack Lake revealed some surprises that changed the way we look at the lake. Previously assumed to be a bathtub about 6’ deep, we found Tamarack actually has two deep pockets that are 9-10’ deep.

So what does this mean for the lake, and what can we do with this knowledge? 

The depth and shape of the lake influence plant growth, how fish behave, and how nutrients cycle in the lake. Deep pockets imply that fish are able to overwinter in these spaces, benefiting from deeper, colder water that can hold more dissolved oxygen. This knowledge also helps us puzzle-piece the role aquatic plants play in the lake. Aquatic plants typically thrive 4-6’ deep. If there’s a deep spot free of aquatic plants, we know that nutrients are being held either in the water column or in the lake bottom. Because aquatic plants also hold nutrients, we can take all these factors and form a picture of what the lake’s ideal would be, striving for realistic goals in water quality improvement.

 Watershed management organizations such as VLAWMO use this insight to:

  • Customize monitoring according to the unique character of the lake. Will a simple surface sample be sufficient, or will deep pockets indicate we should take samples at different depths to understand the layers and cycling of the lake (also known as stratification)?
  • If an aerator is of interest to prevent winter fish kills, where is the most effective place to put it?
  • In the case of Charley lake, VLAWMO as well as local residents are interested in knowing more about sediment build-up in the lake. Charley Lake is the first lake to receive water from the conduit that brings water from the Mississippi, which then follows down the Vadnais Chain of Lakes to Vadnais Lake, which is the drinking water source for the Saint Paul Regional Water Services (SPRWS). If augmentation should occur from the Vadnais Chain of Lakes to feed into White Bear Lake, would more water in the system bring more sediment to Charley Lake? Having a baseline now will allow us to track changes over time.

What are the results? Read about what we found!

Charley Lake Results

Wilkinson Lake Results

The bathymetry studies are a first step in deepening our knowledge of our local lakes, as each one has unique characteristics. Knowing these details helps us make better management decisions, and prepares us with a baseline to refer to if something unexpected happens in the future. Find more information on each lake in VLAWMO on our waterbodies page.

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