Photodissociation dynamics of H2O at 121.6 nm through the (B) over tilde(1)A＇(1) state have been studied using the high-resolution H atom Rydberg tagging technique. Experimental evidences show two different dissociation pathways to form the ground OH (X,v=0) products: dissociation through the B (B) over tilde-(X) over tilde conical intersection, and dissociation through B (B) over tilde-(A) over tilde Coriolis coupling. By preparing the H2O molecules at higher rotational temperatures, dissociation through the B (B) over tilde-(A) over tilde Coriolis coupling pathway can be enhanced.