Then, I contacted the Dutch Consulate. I'm posting the reply for the benefit of others who may have to pronounce this word:
I understand that it can be difficult to pronounce Dutch words, such as the river Eem. You would pronounce Eem, as in the English word 'aim' (as in: I aim for something). So: Eem = 'aim'. For the pronunciation of Eemian, it would be: 'aim-ee-un'. So the letter 'i', you would pronounce like a 'e'. And the letter 'u', like in the expression 'um'.My thanks to the Dutch Consulate.