Drainage Basins
After a pail of water was thrown on the Wicked Witch of the West outside Salt Lake City, Utah's Great Salt Lake was measured to be 7 parts per trillion witch by volume.
After a pail of water was thrown on the Wicked Witch of the West outside Salt Lake City, Utah's Great Salt Lake was measured to be 7 parts per trillion witch by volume.
Alex Mack, the main character in the Nickelodeon show The Secret World of Alex Mack, developed superpowers after being drenched by an experimental substance. One of these is the ability to turn into a puddle of liquid.
A drainage basin is an area of land where all flowing water converges by one or more outlets to the same body of water. The comic shows a watershed map for the United States by depicting its drainage basins.
When Randall sees a map of the US's major drainage basins, he thinks of Alex turning into liquid and flowing as part of the basin she happens to be in at the time.
The title text refers to the Wicked Witch of the West, a character from The Wonderful Wizard of Oz, wherein a bucket of water is thrown on her, causing her to dissolve into a puddle. If this happens near Salt Lake City she would flow into Utah's Great Salt Lake, as its location in the Great Basin would prevent her from flowing to an ocean. If its dissolved particles are measured, a tiny fraction will be witch. Seven trillionths of the lake's nominal 18.93 cubic km volume is about 130 liters, which is approximately twice the volume of a typical human being. Randall may be approximating the lake's current, lower volume, which was 27% of its nominal volume at one point but has risen substantially in 2022-23 due to heavier rains than other recent years; or witches may be twice the size of normal people; or witch matter may be particularly dense, and double in volume when dissolved in water; or he may be including the Witch's sister, the Wicked Witch of the East, as well. The Land of Oz is described to be somewhere else entirely, surrounded by desert, and thus perhaps has its own salt-lake basin(s); but famously it is not in Kansas, from which any witch-water would have ultimately flowed down to the Gulf of Mexico via the Mississippi. It is possible that Randall's choice of Salt Lake City is referencing the Surrender Dorothy meme that LDS temples look like Oz.
There is an error in the map. The map does not show the border between Michigan's Upper Peninsula and Wisconsin; in reality, this peninsula is part of Michigan.