Si Shui Gate is very similar to Hu Lao Gate. In alot of stages, Lu Bu will appear here but in Guan Yu's story he only appears in Hu Lao. It's pretty straight forward and you can basically open the supply route for Sun Jian right away cuz you start right next to Yuan Shu. The only thing to look out for is Hua Xiong gets full morale and charges Yuan Shao once he gets near.