Maybe it will be improved some time. But fluid physics simulation is a discipline of it's own. Especially if it takes volume into account and since we have voxel base here it HAS to take volume into account if it should show some nearly realistic behaviour. And that means, it is not just hard to do such calculations, it will also cause inherently heavy cpu load. It is nearly comparable to structural integrity.
I remember there was a mod for minecraft, that added "realisitc" water simulation to the game. It worked nicely for small constructions that used little water, but with increased size it even overwhelmed the fastest CPUs. And they even skipped the realistic calculation for huge natural amounts like rivers and lakes. So you still couldn't build something like a dam and expect the river to back up and increase water level. That's why the mod was discontinued early.
But yeah, they should really implement at least some rudimentary mechanics like in minecraft. Like a block of water causes flow to the next 7 blocks and a block of water will always casue a direct flow down until it reaches some solid block.
And also integrate height levels into RWG. It's just anoying that every occurence of natural water is on sea level, and if the terrain is elevated, you always have a crack, where a river is.
