One of the main goals of the LOCSS Project is to monitor change in lake water storage over time. The first step in being able to do this is collecting lake level measurements. That’s what you all, our citizen scientists, provide us with when submitting lake level measurements from the gauges. The next step in being able to do this is collecting lake surface area measurements. To do this, we use satellite imagery from the Landsat and Sentinel 2 satellites over each of our LOCSS lakes. We then calculate what the surface area is of the lake in each image. Once we have both data sets, we combine them to get lake water storage. We use measurements taken on the same day (or ± 1 day) and plug them into a formula based upon the formula of a trapezoid:
It is important to note that we are calculating the change in volume, not the absolute volume. Once we plug in all of the measurement pairs, we get a nice time series of change in lake water volume.
Once we have the time series of change in lake water volume for each lake, we can compare what we are seeing in each lake in each study region. To do this we look at the correlations between the change in lake water volume between pairs of lakes, or how the lake volumes are changing similarly or differently. We also look at how the correlations change based upon the distance of the lakes from one another. This series of blog posts will discuss what we found in each region after running these analyses.
This is the first in a series of posts where we explore what we have learned about our lakes. Other posts include:
Future posts will share what we have learned about our study lakes in Washington and Illinois.
We share stories about the lakes in our study, our partners and volunteer citizen scientists, as well as interesting results from our research.