[villagetinker]

I agree with above the underground lines go to a 'pop-up' or a grated drain where the water go out to the yard. Now your task will be to find the end of the run. I you have a snake or can borrow one, you may be able to insert the snake where the downspout connects, then keep inserting it until it stops. Make the snake, and remove, then layout across the yard and mark an arc for possible locations. I then used a Philips screw driver to probe the area for the pop-up took about 2 hours for each one, but I found them. I then removed these and installed short extensions so they were slightly below the mowed grass. seems to be working so far.