Ecohydrological Model for Grasslands Lacking Historical Measurements II:
Confluence Simulations Based on Dynamic Channel Parameters
Technology has greatly promoted ecohydrological model development, but
runoff generation and confluence simulations have fallen behind in
ecohydrological model development due to limited innovations. To fully
understand ecohydrological processes and accurately describe the
coupling between ecological and hydrological processes, a distributed
ecohydrological model was constructed by integrating multisource
information into MYEH. We mainly describe runoff generation and
convergence modules. Based on the improved HBV model and degree-3 hour
factor method, runoff generation and snow routines were constructed for
semiarid grassland basins. In view of meandering and variable steppe
river channels and steep hydrological relief characteristics, a
confluence module was constructed; the 1-km bend radius equivalent
concept was innovatively proposed to unify river channel bend degrees.
The daily runoff simulation validation results obtained using two
datasets were R2=0.947 and 0.932, NSE=0.945 and
0.905, and KGE=0.029 and 0.261. In the 3-hour flood simulations, the
MYEH model could better restore small long-distance water flows than the
confluence method that did not consider actual river lengths or bend
energy losses; the MYEH model more accurately simulated the flood peak
arrival time than the confluence method that did not consider overflow.
The simulated mainstream overflow frequency increased by 0.84/10 years,
and significant interaction periods of 10 to 13 years occurred with
local precipitation, ecological status and global climate change. An
approximately 2-year lag occurred in the global climate change response.
This study helps us further understand and reveal the ecohydrological
processes of steppe rivers in semiarid regions.