Improvement　of　water　environmental　quality　in　inland　river　networks　can　usually　be　achieved　by　water　replacement.　For　a　network　of　constant　inflows,　optimization　of　its　flow　diversion　has　been　one　of　the　approaches　to　implementation　of　water　replacement　in　its　different　branches.　Due　to　the　close　morphological　relation　between　flow　diversion　and　geometrical　characteristics　of　the　channel,　a　special　master-slave　relationship　of　the　channel　cross　section　and　longitudinal　profile　versus　the　discharge　of　the　river　network　will　be　developed.　In　this　paper,　geometrical　characteristics　are　considered　as　slave　variables,　such　as　the　river　length　l,　slope　bottom　i　and　bifurcation　angle　α,　and　their　different　weights　in　prediction　of　the　discharge　in　each　network　branch　were　obtained　using　fuzzy　comprehensive　evaluation　(FCE)　based　on　the　fuzzy　theory　and　rough　set　theory.　To　verify　this　method,　a　FCE　model　was　successfully　applied　to　a　hydrodynamic　environment　study　for　the　inland　river　diversion　project　of　Fuzhou.　The　results　are　helpful　in　planning　water　distribution　and　scheduling　operation　schemes　for　the　river　network.　©　2016　All　right　reserved.