Why is the Canal Nearly Empty?
Is it so Good Samaritans like this guy can clean it up? Anyway, why not grab a trash bag and go help out? You’ll make the water a little less toxic and who knows what treasures you’ll find among all the boots, syringes, shredded White House documents and empty bottles of Night Train and Thunderbird?
They drain the canal peridoically for 3 main reasons:
1. If the Potomac rises to a certain level the canal can reach flood height, so they drain it to preempt overflow onto the canal banks.
2. When the Potomac reaches flood heights, usually after the winter months, many fish get caught in the canal. So they usually drain the canal once or twice a year back into the Potomac as a more humane way to return fish to the river. (The alternative fish return method is to stun them and net them and dump them back in the river).
3. Canal repair.
I knew someone in the comments would make up for my lack of research. Thank you sir!