This study develops a multivariate eco-hydrological risk-assessment framework based on the multivari-ate copula method in order to evaluate the occurrence of extreme eco-hydrological events for the Xiangxi River withi...This study develops a multivariate eco-hydrological risk-assessment framework based on the multivari-ate copula method in order to evaluate the occurrence of extreme eco-hydrological events for the Xiangxi River within the Three Gorges Reservoir （TGR） area in China. Parameter uncertainties in marginal distri-butions and dependence structure are quantified by a Markov chain Monte Carlo （MCMC） algorithm. Uncertainties in the joint return periods are evaluated based on the posterior distributions. The proba- bilistic features of bivariate and multivariate hydrological risk are also characterized. The results show that the obtained predictive intervals bracketed the observations well, especially for flood duration. The uncertainty for the joint return period in ＂AND＂ case increases with an increase in the return period for univariate flood variables. Furthermore, a low design discharge and high service time may lead to high bivariate hydrological risk with great uncertainty.展开更多
Assessing environmental flows （e-flows） for urban rivers is important for water resources planning and river protection, Many e-flow assessment methods have been established based on species＇ habitat pro- vision re...Assessing environmental flows （e-flows） for urban rivers is important for water resources planning and river protection, Many e-flow assessment methods have been established based on species＇ habitat pro- vision requirements and pollutant dilution requirements, To avoid flood risk, however, many urban rivers have been transformed into straight, trapezoidal-profiled concrete channels, leading to the disappearance of valuable species, With the construction of water pollution-control projects, pollutant inputs into rivers have been effectively controlled in some urban rivers, For these rivers, the e-flows determined by tradi- tional methods will be very small, and will consequently lead to a low priority being given to river pro- tection in future water resources allocation and management, To more effectively assess the e-flows of channelized urban rivers, we propose three e-flow degrees, according to longitudinal hydrological con- nectivity （high, medium, and low）, in addition to the pollutant dilution water requirement determined by the mass-balance equation, In the high connectivity scenario, the intent is for the e-flows to maintain flow velocity, which can ensure the self-purification of rivers and reduce algal blooms; in the medium connectivity scenario, the intent is for the e-flows to permanently maintain the longitudinal hydrological connectivity of rivers that are isolated into several ponds by means of weirs, in order to ensure the exchange of material, energy, and information in rivers; and in the low connectivity scenario, the intent is for the e-flows to intermittently connect isolated ponds every few days （which is designed to further reduce e-flows）, The proposed methods have been used in Shiwuli River, China, to demonstrate their effectiveness, The new methods can offer more precise and realistic e-flow results and can effectively direct the construction and management of e-flow supply projects,展开更多
基金This work was jointly funded by the National Natural Science Foundation of China （51520105013 and 51679087） and the National Key Research and Development Plan of China （2016YFC0502800）.
文摘This study develops a multivariate eco-hydrological risk-assessment framework based on the multivari-ate copula method in order to evaluate the occurrence of extreme eco-hydrological events for the Xiangxi River within the Three Gorges Reservoir （TGR） area in China. Parameter uncertainties in marginal distri-butions and dependence structure are quantified by a Markov chain Monte Carlo （MCMC） algorithm. Uncertainties in the joint return periods are evaluated based on the posterior distributions. The proba- bilistic features of bivariate and multivariate hydrological risk are also characterized. The results show that the obtained predictive intervals bracketed the observations well, especially for flood duration. The uncertainty for the joint return period in ＂AND＂ case increases with an increase in the return period for univariate flood variables. Furthermore, a low design discharge and high service time may lead to high bivariate hydrological risk with great uncertainty.
文摘Assessing environmental flows （e-flows） for urban rivers is important for water resources planning and river protection, Many e-flow assessment methods have been established based on species＇ habitat pro- vision requirements and pollutant dilution requirements, To avoid flood risk, however, many urban rivers have been transformed into straight, trapezoidal-profiled concrete channels, leading to the disappearance of valuable species, With the construction of water pollution-control projects, pollutant inputs into rivers have been effectively controlled in some urban rivers, For these rivers, the e-flows determined by tradi- tional methods will be very small, and will consequently lead to a low priority being given to river pro- tection in future water resources allocation and management, To more effectively assess the e-flows of channelized urban rivers, we propose three e-flow degrees, according to longitudinal hydrological con- nectivity （high, medium, and low）, in addition to the pollutant dilution water requirement determined by the mass-balance equation, In the high connectivity scenario, the intent is for the e-flows to maintain flow velocity, which can ensure the self-purification of rivers and reduce algal blooms; in the medium connectivity scenario, the intent is for the e-flows to permanently maintain the longitudinal hydrological connectivity of rivers that are isolated into several ponds by means of weirs, in order to ensure the exchange of material, energy, and information in rivers; and in the low connectivity scenario, the intent is for the e-flows to intermittently connect isolated ponds every few days （which is designed to further reduce e-flows）, The proposed methods have been used in Shiwuli River, China, to demonstrate their effectiveness, The new methods can offer more precise and realistic e-flow results and can effectively direct the construction and management of e-flow supply projects,
