Question
I live in western Colorado (zone 5). The landscape is sloped to where my front yard gets alot of sprinkler run-off keeping the area very wet. Due to our very hot summers we need to water deeply twice a week in order to maintain a healthy lawn. Unfortunately, I cannot plant in a drier location nor can I change the slope of the ground. I need to work with what is there.
I currently have a weeping cherry and half the leaves have already turned yellow after 2 months.  The soil is clay which has been amended with cotton bur and root stimulator added when it was planted. I know I am losing this beautiful tree. I would like to replace the weeping cherry with one that can tolerate lots of water and will keep its growth to about 15'.
I was thinking of a River Birch.  Please advise.  
Thank you for your prompt response.

Answer
River birch should work or a weeping willow will also work. Willows need more water than most trees and should be good in the site conditions. I would wait and plant a replacement in the Spring this will give any tree a better chance to survive.

Here is a web link to more infromation on weeping willow and river birch.

http://hort.ufl.edu/trees/SALSPPA.pdf

http://forestry.about.com/od/treeplanting/p/good_rbirch.htm