Abstract: Due to complex flow patterns,the confluence or diversion port of braided river is often encountered with estuarine beaches and deep channels.The complex and diverse hydrologic conditions provide a good habitat for fishes.In line with the complex boundary of braided river,a two-dimensional mathematical flow model based on the general curve coordinate system is established and applied to the construction of ecological river network and fish habitat design of the left bank of Angu hydropower station in Leshan reach of Dadu River.The water depth,flow velocity,flow field and diversion ratio of the river reach before and after the project are simulated and compared.By implementing ecological engineering measures in the ecological river channel on the left bank,the water flow characteristics of the spawning area still meet the requirements of fish habitat.In terms of the operation effect of Angu hydropower station,the designed ecological measures have achieved good practical effect on the improvement of fish habitat in river.

Key words: braided river channel, fish habitat, curvilinear coordinates, plane two-dimension mathematical model, rule of water flow movement