Extremely Low Flows - What could I be possibly doing wrong?

[Ian]

Hi, 

I was running Storm Injector v1.3.6.0 for a massive catchment (1127.4 ha) catchment and was getting very low flows (3 m3/s  and 13m3/s) downstream compared to WBNM (which is often the one I use to confirm) - I was expecting around  80 m3/s to 100m3/s for the 5% AEP .

I ran the same catchment on WBNM and was getting 90 m3/s - 100m3/s,

Any thoughts on what I could be possibly doing wrong? 

Cheers!