airs,
which we term downstream hydrologic distance. In contrast, the
total hydrologic distance is used for modeling flow-connected
pairs, which we term total hydrologic distance.</p>
<p>A downstream hydrologic distance matrix provides enough
information to meet the data requirements for both the tail-up and
tail-down models. When two locations are flow-connected, the
downstream hydrologic distance from the upstream location to the
downstream location is greater than zero, but it is zero in the
other directi