Unfortunately there is no easy way of suggesting how much water a hedge will need. It changes from hedge to hedge.
Underwatering will cause the leaves to burn, and if not caught quickly enough, the plants will die. You only need to get this wrong once to undo all the hard work put in. On the other hand overwatering can be just as serious. This can cause the leave to droop and the plants to decay from fungal or bacterial rots.
If you treat the hedge as a large pot plant for its first year. You must assume it cant get water for its self and that rain will not provide enough water to sustain the plants needs.
We can supply Techline irrigation which has pressure valves every 30cm ( 12" ) that drip .3 of a litre an hour. We also stock "Rain Bird" Automatic water valves. You can set the frequency of watering and length of each watering cycle.