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I have two point layers, one is set of origin points and one is a set of destination points, each with 608 points. Object IDs match the origins to the destinations. The points are all snapped to the National Hydrography Dataset (NHD) streams. I am working in ArcMap 10.5.

I need to find the distance between the paired points along the NHD stream network, AND state whether the route is upstream or downstream.

Edit 1: Image added by request. In this example, the destination point is upstream of the origin point along the route I highlighted. There are several other destination points which are closer. I need the distance and direction (upstream/downstream) to the matching destination point only. There are 608 of these pairs across the study area. enter image description here

I have successfully found the distance between origins and destinations along the NHD network, as shown in the image, by generating an OD Cost Matrix in Network Analyst, adding origins and destinations, and selecting the lines where origin ID = destination ID. However, this does not include whether the destination is upstream or downstream.

One potential option would be to find a way to trace upstream of each origin point until reaching the correct destination point. If it does not find the correct destination point upstream, then it could be assumed that the destination point is downstream (or vice-versa). Tracing a geometric network have a way to do this, but I cannot find a way to implement this to find the paired destination point, rather than just finding the closest destination point.

Any ideas for finding the distance and direction along a stream network between pairs of points?

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    Welcome to GIS SE! What is "NHD" network? A picture could go a long way in explaining what you're trying to do here - would you please edit your question to include a sample picture, preferably labelled to help explain what you're asking? – Midavalo♦ Jul 10 '20 at 19:50
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    Example shown tells that destination point is not reachable from matching source. – FelixIP Jul 11 '20 at 1:23
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RivEX can link sites, assuming the network is not huge. But I doubt any tool will tell you if the relative direction is u/s or d/s. How do you measure if something is d/s of you, you could initially head down stream then head of up a tributary much further, is that considered "downstream". Elevation won't necessarily guarantee if something is d/s, nor distance from network mouth. Your image starting at the yellow star initially heads downstream then heads upstream, so is the green star upstream? You need to be more explicit about that rule if in fact it is of any value?

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