  We consider the tributary structure of Howard's drainage model studied by
Gangopadhyay et. al. Conditional on the event that the tributary survives up to
time $n$, we show that, as a sequence of random metric spaces, scaled tributary
converges in distribution to a continuum random tree with respect to Gromov
Hausdorff topology. This verifies a prediction made by Aldous for a simpler
model (where paths are independent till they coalesce) but for a different
conditional set up. The limiting continuum tree is slightly different from what
was surmised earlier. Our proof uses the fact that there exists a dual process
such that the original network and it's dual jointly converge in distribution
to the Brownian web and it's dual.
