One of them is per family and other per person (family of size 1). Is it even comparable? I am not saying it is lesser, it's pretty high, probably 200% not 560% if I am right.
That's more than 5x less than the US. It's quite plausible the average family size and environmental conditions in Flanders differ quite a bit from that in the US, but it's still a huge disparity, and according to the second link a lot of that seems to be down to domestic irrigation. Tackling that wouldn't be very popular, of course.