Variations in the Runoff-Sediment Relationship of the Weihe River Basin Based on the Copula Function

Sediment load and its response to the variations of the hydrological elements are important for the healthy utilization of a river. In this study, the response of sediment load to hydrological change was explored in the upstream part of the Lancang-Mekong River, a major transboundary river originating from the Tibetan Plateau and running through China, over the past 50 years. A sediment rating curve for the Jiuzhou Station was developed based on the available SSC-Q (suspended sediment concentration (SSC) and flow) data and trends in annual precipitation, runoff, peak flow (PF), low flow (LF), maximum water level (MWL), and sediment load were analyzed from 1957 to 2006. The correlation analysis method and Random Forest (RF) were adopted to qualitatively and quantitatively quantify the contribution of each hydrological element to the sediment load change. Results indicated that both the runoff and sediment load showed a significantly upward trend, especially after 1979, at the 95% confidence level. The sediment load had significantly positive correlations with runoff, PF, and MWL at the 99% confidence level, respectively. In particular, the sediment load had the largest significant positive correlation with runoff since 1980. Runoff had the largest variable importance to the sediment load change, followed by PF, MWL, precipitation, and LF. The increasing trend in the sediment load was mainly attributed to the increase of runoff in the upstream part of the Lancang-Mekong River since the mid-1980s.

Section: Relationships Of Sediment Load Between Runoff Mwl Pf and Lfmentioning

confidence: 99%

Response of Sediment Load to Hydrological Change in the Upstream Part of the Lancang-Mekong River over the Past 50 Years

Gui

et al. 2018

“…Evidently, a water and sediment joint distribution should be developed to indicate the correlation between a flood and sediment. As is commonly applied in the hydraulic field [53][54][55], the theory of the Gumbel-Hougaard (GH) copula function [56] is introduced for coupling the flood and sediment variables. Expression (11) can reflect the marginal distribution characteristics of the peak flood volume towards the sediment parameter, and describe the nonlinear relationship between flooding and sediment.…”

Section: Coupling Of Flood and Sediment Uncertaintiesmentioning

confidence: 99%

Assessment of Sediment Impact on the Risk of River Diversion during Dam Construction: A Simulation-Based Project Study on the Jing River, China

Song

Liu

et al. 2018

Dams are vital for water resource utilization, and river diversion is key for dam construction safety. As sandy river basins are important exploitation areas that have special diversion features, the impact of sediment on the risk of river diversion during dam construction should be assessed. Diversion uncertainty is the origin of diversion risk, and sediment uncertainty changes the storage and discharge patterns of the diversion system. Two Gumbel-Hougaard (GH) copula functions are adopted to couple the random variables of flood and sediment, so that the sediment impacts on diversion storage and discharge can be obtained by the sampling of flood peaks. Based on variable coupling and sediment amendment, a method of Monte Carlo simulation (MCS) with a water balance calculation can quantitatively assess the risk of sandy river diversion, by evaluating the probability of upstream cofferdam overtopping. By introducing one diversion project on the Jing River in China with a clear water contrast, the risk values of dam construction diversion with or without sediment impacts can be obtained. Results show that the MCS method is feasible for diversion risk assessment; sediment has a negative impact on the risk of river diversion during dam construction, and this degradation effect is more evident for high-assurance diversion schemes.

“…Additionally, some scholars analyzed the encounter frequency of the high-low runoff-sediment of several variables through 3D-symmetric copula and non-symmetric 3D and 4D copula of particular structures [17,18], but the particular structures were limited, to some extent, and their parameters were, at times, complicated for finding the solution. The study of using copula functions to analyze the relationship between runoff and sediment is given in [19]. Empirical formulae and other deterministic methods were also used in the study of the runoff-sediment relationship [20], but these deterministic methods ignored the randomness of the variables.…”

Section: Introductionmentioning

confidence: 99%

“…The climate in the WRB is a warm-temperate, semi-wet, and semi-arid monsoon climate, with characteristics of a mountain basin climate. The average temperature of WRB in a year is 12.8 • C [19].…”

Section: Brief Introduction To the Research Areamentioning

confidence: 99%

Probability Analysis and Control of River Runoff–sediment Characteristics based on Pair-Copula Functions: The Case of the Weihe River and Jinghe River

You

Jiang

Liu

et al. 2019

Analyzing the encounter frequency of high–low runoff and sediment yield is important for the appropriate dispatching of runoff–sediment resources, as well as river regulation. However, there have been no reports on the utilization of the pair-copula function in analyzing the runoff–sediment characteristics from a probabilistic perspective and conducting probability control on the runoff–sediment yields of different hydrologic stations. This paper builds marginal distribution functions on the basis of kernel distribution theory. In addition, this paper builds the joint distribution functions through pair-copula functions in order to analyze the encounter probability and the compensation characteristics of high–low runoff and sediment at different stations on the Weihe River in China, as well as the origins of runoff–sediment, to conduct probability control of river runoff–sediment resource allocation. The results show that, in different periods, the synchronous probability of high–low runoff of the Weihe River’s Xianyang and Huaxian Stations, and the Jinghe River’s Zhangjiashan Station differ, while that of high–low sediment at the three stations changes little—remaining at around 54%. Therefore, the sediment and runoff of the Weihe River apparently have different origins. In years of high and low runoff, if the runoffs of the Xianyang and Zhangjiashan Stations can be kept within a certain range, then the runoff of the Huaxian Station will be in a particular range, at a certain probability. Sediment at the Huaxian Station can be controlled, in a similar way. These results are of great significance for the water and sediment management department of the Weihe river, in order to reasonably allocate water and sediment resources.