Why do I get similar result in Flow Simulation?

Hello guys. This is my 1st time using Flow Simulation in Solidworks. I am tasked to simulate a lagoon with different Volume Flow inlets. For example, I've tried putting 300 m^3/s and 3000 m^3/s as the inlet and 101325 Pa Environment Pressure.as the outlet I use global coordinations as the inlet and the outlet reference. I included Global mesh with level 4 initial mesh as well. Whenever I vary the value of my inlet, I get the same result. I've tried decreasing the outlet and the same thing happens. In what way can this issue be overcome? Is there anything I haven't done? Am I missing something? Here's the picture for the reference.

PS:I have now uploaded the parts file and the assembly part@

SolidworksFlow Simulation