Question
My wife and I planted the Paper Bark River Birch last year, and we've been having problems.  Last year after we planted it, one of the shoots didn't have many leaves on it.  This year the Tree leaves were numerous, then about a month ago I noticed that some of the leaves were turning yellow and falling off the tree.  Then everything seemed to green up once again.  Last weekend (7/12-13) I noticed the leaves turning yellow again.  This weekend (7/19-21) numerous leaves were on the ground.

We haven't been receiving a lot of rain lately, do we need to water it?  Or is there something else that could be wrong?

Answer
River birch needs more water than most trees. The name implies it grow naturally along rivers.
Water with 1 inch of water every third day until it rains, then once a week. Place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop, Of you have not done so mulch around the tree out to about three feet with not more than 3 inches of organic mulch not piled up on the trunk. This will help hold moisture around the tree.