From Hangzhou Airport to Anji, you could reserve a car in advance which will take you to the reservoir directly, the fare should be no less than 500RMB.

On the other hand, if you arrive in Hangzhou in daytime, you four could take a taxi to Hangzhou North Bus Station where there are frequent buses departing to Anji Town from 06:20 to 18:30. The taxi fare is about 100RMB. The bus fare is 26RMB per person and takes one hour on the way. When you arrive in Anji, hire a local cab to the reservoir with a fare of about 60RMB.