It's worth noting that there is a theory that the Biblical flood was caused by a massive geological catastrophe along the undersea fault lines, likely the Mid-Atlantic considering the final location of the Ark was Turkey. The sudden lava flows caused huge amounts of moisture to evaporate, and the earthquakes caused widespread tsunamis.
A similar concept could be applied to the Calamity of Water. As suggested above, it's possible Othard suffered a draught while Aldenard was flooded.
On an entirely different note, since Ala Mhigo is heavily inspired by Turkey, Nyunkrepf's Ark being up in the mountain made me happy.
