I strongly agree with 'kooswillem' post to have springs up in the mountain and let water find it's way down, from there you can dig a trench to your settlement letting the water also run your way.
Make fishing for trout only possible in rivers close to the mountain, as trout always travels up stream once a year, the rest of the year they are in deep sea.
On that note to make waterways to your town it would also be a nice idea to have a trench surrounding your castle walls and have a drawbridge kind of gate expanding over the water trench.