A study of the hydraulic parameters and ecological significance of
braided rivers under flow variations
Numerical modeling of braided channels showed no significant differences
in the number of cross-sectional branches between different water
periods in the middle reaches of the Yarlung Tsangpo River. During most
of the year (wet, normal and dry periods), flow velocities in the
higher-branching (HB) channels were significantly lower than in the
other two branching categories, while the overall distribution of depth
in the higher-branching channels maintained a high degree of consistency
with the moderate-branching channels (MB), which partly explains why the
HB channels are important habitats for fish spawning, nursery and
baiting (lower flow velocity distribution with a wider range of depth).
Based on the examination of the water surface width, the water surface
width may not be a limiting factor for fish habitat within braided
rivers. Simulation of the hydrodynamic parameters of the fish-spawning
grounds revealed that the average cross-sectional flow velocity and
water depth fluctuated the least at different flows during the
fish-spawning period for the HB channels. By counting the hydraulic
parameters of the spawning grounds during the spawning period, it can be
seen that the most preferred flow velocity for fish in the braided river
in the study section was 0.1-0.4 m/s, and the water depth was 0-1.2 m.
This article analyses the characteristics of the hydraulic parameters of
the braided river and provides theoretical support for the restoration
of fish habitats in braided rivers.