Hello everybody!
Does anyone have an idea why rivers don’t work with world partition?
The rivers remain permanently visible when the world partition is activated
Specifically, I use the water system from unreal engine, and I use the UE5.2.1 version
Did you figure this out?
I’m also very curious how it is supposed to work - AFAIK Unreal decides to load spatial actors according to their bounding box (though you can switch to actor location) and a long, meandering river can have a huge bounding box so it may look like always loaded.
Anyway, the water system unfortunately is still experimental with lot of issues 
Hello!
Unfortunately, I did not manage to make it work
I’m not sure it solves your problem but I came to the following solution in many bloody hours 
First I created own blueprint based on Unreal’s River Body BP and I switched off “Affects Landscape” by default and I added this version to the map to avoid breaking World Partition. (Some defaults like river materials need to setup again, seems it not initialized correctly if I use this child class)
Second important thing I also disabled “Affect Height Map” in the Water Brush Manager.
Now my rivers are loading/unloading with tile and no more full landscape loaded issue.
Of course it means landscape will not affected, but it wasnt an issue for me as I’m working with presculpted river beds.
P.S. found a topic about it, it adds you need also delete Water Brush Manager which will be regenerated next editor start.
Hello!
Thanks for the information, unfortunately I want the river to affect the landscape
Hi,
I made a temp work-around by defining a specific grid called ‘WaterGrid’, that has a very small loading range.
Luckilly rivers and lakes connect quite well (if you set the spline settings at the end points exactly the same for a river, otherwise you get strange flow visual issues), so you can split your big river into smaller pieces & load them seperately.
Hope this helps for now.
Kr, Flutebox