Remote Sensing & Lagoons: How to measure inundation with aerial images

Hey geo-loves! Hope everyone was able to enjoy the weekend despite the political events that recently transpired. Going to the Women’s March in Boston last week was a really inspiring way to see people come together.

One of my photos from Instagram of the protest last weekend.

So, I’d like to talk a little bit more about my lagoons (they feel like my lagoons because I look at them so much!) and what I’m doing with them. Right now, I’m developing remote sensing for my lagoons in Salar de Atacama in Chile. What is remote sensing? It’s when you take satellite data (which in my case are images) and manipulate that data to get information.

In my case, I’ve been taking images of my lagoons and outlining the extent of their surface area in ArcGIS. By outlining the lagoons, I’m able to measure how the surface water expands and retreats through time. I am specifically focusing on a time period after a large precipitation event that occurred in March of 2015 to see how the lagoons responded to precipitation-driven recharge. Here’s a “before and after” shot of the lagoons on March 17, 2015 versus May 20, 2015.

Can you see the difference?

There’s a pretty noticeable difference, isn’t there? To measure the surface area of the lagoons, I draw polygons around the surface water extent and then use ArcGIS to measure their surface area.

I’m really excited for some new maps with even better resolution that will come out on the Landsat Imagery website later in February. I’m also excited to take this remote sensing a step further and measure the coloration of the pixels in each image to get even more accurate surface area measurements.

So what do we see in these lagoons’ responses to the March 2015 storm? First, we see that not all lagoons react uniformly. Those differences in response may indicate variations in topography, in discharge, or in recharge based on each locale’s stratigraphy. Second, we notice that the most recent lagoon changes may be a part of an ongoing decline in the over all extent of lagoons throughout the salar.

Why are these variations in lagoon surface area occurring? That’s for me to explore further in my thesis, and I’ll make sure to keep you guys updated every step of the way. In the mean time, feel free to comment on this post or e-mail me with questions or thoughts! Have a good weekend!