Otherwise my imaginary figures above seem broadly in line with the Zeuss's sane ones.
My only issue so far is with your ‘1L’.
3.8L/day comes from total amount evaporated divided by number of days. If you only consider the first day, this actually rises to 10L/day.
If you search for “Kirk Watch”, there’s a post (maybe a couple below that one) where I justify the numbers used in the spreadsheet. Or perhaps "thirsty cat” might find it quicker.