Estimated Watershed Runoff - an example of analysis and cartography
- artlembo
- Mar 24
- 2 min read
I was inspired by a map that my good friend Chul Sue Hwang made for South Korea that showed watershed discharge for the nation:
It's just an incredibly beautiful map, and it helps understand the geography of South Korea and the influence of the summer monsoon season.
I asked the USGS if we had a map like this, and I came to find out that we do not. That presented a nice challenge: make the first map to show average monthly runoff by major watershed in the conterminous United States.
Well, it's hard to rival the work that Chul Sue does, but I thought I'd give it a try. But to do so would require some analytical skills along with some cartography skills. I love looking at beautiful cartographic maps, I hate making them. Years ago when my colleague Mike Scott was teaching Cartographic Visualization, I overheard a funny observation that a student made:
I figured it out. With Dr. Scott, you have to make your map look really good. With Lembo, he doesn't care how it looks, so as long as the process runs really fast.
So yeah. I'm more about analytical processing than cartography. Anastassiya Suprunova now teaches our Cartographic Visualization class, so I got one of her undergraduate students, Will Edmunds, to work with me to make the map for his final project. Before talking about how the map was made, the following is Will's map showing average monthly runoff for each major watershed region (HUC2) in the conterminous United States.
I think Will did an excellent job making this map. In South Korea, they only have 5 major watershed regions, whereas we have 18 in this map. Screen/map real estate was a big challenge. Also, we have very different densities of our river network, so Will had to be aware of line widths and text placement.
Some of the decisions that Will had to make included:
how to fit 18 watersheds and their corresponding graphs on a single presentation.
how to mask regions outside of the United States but still show continuity of physiography.
how to create boundaries between watersheds that were more artistic in nature.
what data to bring in, what to leave out, and what resolution to support.
Also, preparing the data required a little bit of thought. So, our next post will discuss how we obtained and processed the data, and then after that, I'll have Will take a deeper dive into some of the cartographic decisions he made to complete the map.
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