Evaluating environmental flow(EF)is pivotal for conserving and restoring riverine ecosystems.Yet,prevalent EF evaluations presume that a river reach's hydraulic conditions are exclusively governed by inflow discha...Evaluating environmental flow(EF)is pivotal for conserving and restoring riverine ecosystems.Yet,prevalent EF evaluations presume that a river reach's hydraulic conditions are exclusively governed by inflow discharge,presupposing a state of equilibrium in the river channel.This presumption narrows the scope of EF evaluations in expansive alluvial rivers like the Middle Yangtze River(MYR),characterized by marked channel alterations.Here we show the profound channel erosion process and its impact on EF requirements for riparian habitats within the MYR.Our research unveils that:(i)pronounced erosion has led to a mean reduction of 1.0-2.7 m in the riverbed across four sub-reaches of the MYR;(ii)notwithstanding a 37-107%increase in minimal discharges post the Three Gorges Project,the lowest river stages at some hydrometric stations diminished owing to bed erosion,signifying a notable transformation in MYR's hydraulic dynamics;(iii)a discernible rightward shift in the correlation curve between the weighted useable area and discharge from 2002 to 2020 in a specific sub-reach of the MYR,instigated by alterations in hydraulic conditions,necessitated an increase of 1500e2600 m^(3)s^(-1)in the required EF for the sub-reach;(iv)it is deduced that macroinvertebrate biomass rapidly decreases as the flow entrains the riverbed substrate,with the maximum survivable velocity for macroinvertebrates being contingent on their entrainment threshold.These findings highlight the importance of incorporating channel morphological changes in devising conservation strategies for the MYR ecosystem.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.U2040215,51725902,U2240206,52379079)was partly supported by the Natural Science Foundation of Hubei Province(2021CFA029)+1 种基金the Special Project on Knowledge Innovation of Wuhan Science and Technology Bureau(2022020801020132)the Fundamental Research Funds for the Central Universities(2042023kf0160).
文摘Evaluating environmental flow(EF)is pivotal for conserving and restoring riverine ecosystems.Yet,prevalent EF evaluations presume that a river reach's hydraulic conditions are exclusively governed by inflow discharge,presupposing a state of equilibrium in the river channel.This presumption narrows the scope of EF evaluations in expansive alluvial rivers like the Middle Yangtze River(MYR),characterized by marked channel alterations.Here we show the profound channel erosion process and its impact on EF requirements for riparian habitats within the MYR.Our research unveils that:(i)pronounced erosion has led to a mean reduction of 1.0-2.7 m in the riverbed across four sub-reaches of the MYR;(ii)notwithstanding a 37-107%increase in minimal discharges post the Three Gorges Project,the lowest river stages at some hydrometric stations diminished owing to bed erosion,signifying a notable transformation in MYR's hydraulic dynamics;(iii)a discernible rightward shift in the correlation curve between the weighted useable area and discharge from 2002 to 2020 in a specific sub-reach of the MYR,instigated by alterations in hydraulic conditions,necessitated an increase of 1500e2600 m^(3)s^(-1)in the required EF for the sub-reach;(iv)it is deduced that macroinvertebrate biomass rapidly decreases as the flow entrains the riverbed substrate,with the maximum survivable velocity for macroinvertebrates being contingent on their entrainment threshold.These findings highlight the importance of incorporating channel morphological changes in devising conservation strategies for the MYR ecosystem.
