So there's a stable inflow and outflow. I wonder what fractions are dead, wounded (disabled permanently), wounded (temporary), and retired (back to civilian life in one form or another, likely traumatized).
Alternatively, Russia is building up a massive army outside of Ukraine. That seems unlikely though, there's no news about that, I'll discard that hypothesis for now.
Shit is also biodegradable, still not great to have in the river (in large quantities)