The　hydrodynamic　processes　in　estuarine　regions　play　a　crucial　role　in　the　morphological　and　ecological　stability　of　coastal　zones.　As　a　key　hydrodynamic　characteristic　of　bifurcated　rivers,　the　water　diversion　ratio　(WDR)　influences　flow　distribution,　sediment　transport,　and　shoreline　changes　in　estuaries.　This　study　focuses　on　the　lower　Minjiang　River　and　employs　a　MIKE　21-based　two-dimensional　hydrodynamic　model　to　quantify　the　WDR　variations　between　the　South　and　North　Ports　on　the　scale　of　a　tidal　cycle　during　the　wet　season　and　to　reveal　the　regulatory　effects　of　diversion　dyke　length　and　angle.　The　results　indicate　that　the　WDR　of　the　North　Port　exhibits　significant　variation　with　tidal　stages.　The　WDR　of　the　North　Port　increases　with　the　length　of　the　diversion　dyke.　The　current　110　m-long　dyke　has　little　effect　on　regulating　water　flow　between　the　North　and　South　Ports,　and　its　WDR　remains　unaffected　by　changes　in　angle.　In　contrast,　a　450　m-long　dyke　is　highly　sensitive　to　angle　variations.　This　study　not　only　provides　scientific　support　for　channel　regulation　in　the　lower　Minjiang　River　but　also　offers　indirect　insights　into　shoreline　stability　and　ecological　management　under　the　combined　influence　of　human　activities　and　natural　processes　in　estuarine　environments.　©　2025　by　the　authors.