Yichang Hydrological Station Research Articles

A Temporal Convolutional Neural Network Fusion Attention Mechanism Runoff Prediction Model Based on Dynamic Decomposition Reconstruction Integration Processing

Accurate and reliable runoff forecasting is of great significance for hydropower station operation and watershed water resource allocation. However, various complex factors, such as climate conditions and human activities, constantly affect the formation of runoff. Runoff data under changing environments exhibit highly nonlinear, time-varying, and stochastic characteristics, which undoubtedly pose great challenges to runoff prediction. Under this background, this study ingeniously merges reconstruction integration technology and dynamic decomposition technology to propose a Temporal Convolutional Network Fusion Attention Mechanism Runoff Prediction method based on dynamic decomposition reconstruction integration processing. This method uses the Temporal Convolutional Network to extract the cross-temporal nonlinear characteristics of longer runoff data, and introduces attention mechanisms to capture the importance distribution and duration relationship of historical temporal features in runoff prediction. It integrates a decomposition reconstruction process based on dynamic classification and filtering, fully utilizing decomposition techniques, reconstruction techniques, complexity analysis, dynamic decomposition techniques, and neural networks optimized by automatic hyperparameter optimization algorithms, effectively improving the model’s interpretability and precision of prediction accuracy. This study used historical monthly runoff datasets from the Pingshan Hydrological Station and Yichang Hydrological Station for validation, and selected eight models including the LSTM model, CEEMDAN-TCN-Attention model, and CEEMDAN-VMD-LSTM-Attention (DDRI) for comparative prediction experiments. The MAE, RMSE, MAPE, and NSE indicators of the proposed model showed the best performances, with test set values of 1007.93, 985.87, 16.47, and 0.922 for the Pingshan Hydrological Station and 1086.81, 1211.18, 17.20, and 0.919 for the Yichang Hydrological Station, respectively. The experimental results indicate that the fusion model generated through training has strong learning ability for runoff temporal features and the proposed model has obvious advantages in overall predictive performance, stability, correlation, comprehensive accuracy, and statistical testing.

A novel Joint Probability Density Difference Approach for assessing the alteration of hydrologic regime

AbstractThe construction and operation of upstream reservoirs have significantly altered downstream hydrologic regime. Appropriate and quantifiable assessment method for the alteration of hydrologic regime is considerably vital and emergent for ecological protection and restoration. The Range of Variability Approach (RVA) and modified RVA methods have been widely used in practice to assess the hydrological alteration. However, these methods have failed to concurrently describe the distribution of indicator and morphological features in detail, which might inevitably lead to the misjudgment of alteration. This paper proposes a Joint Probability Density Difference Approach (JPDDA) method to address the major drawbacks of these previous methods with the introduction of Gaussian Kernel Density Estimation (KDE) and copula function. The annual average flow is selected as the reference variable to construct a proper joint probability density function between itself and other hydrological alteration indicators. The JPDDA method could describe the marginal distribution in detail through Gaussian KDE and also link the morphological features with copula function. Along with pervious methods, the hydrological alterations at Yichang hydrological station, Yangtze River are estimated based on the measured flow from 1949 to 2022. It is shown that the hydrologic regime has suffered from a moderate or even heavy alteration under the influence of massive upstream cascade reservoirs, and the JPDDA outperforms the other methods in terms of rationality and stability for practical assessments. Thus, the proposed JPDDA method is strongly advised to handle the hydrological alteration and could provide a reasonable reference for ecological operation.

Case Study: Influence of Three Gorges Reservoir Impoundment on Hydrological Regime of the Acipenser sinensis Spawning Ground, Yangtze River, China

After the construction of the Three Gorges Dam (TGD) in China, the downstream has been affected by the reduction in sediment discharge and regulation of flow processes, which have resulted in severe scouring and changes hydrological regime. Consequently, the spawning ground of Chinese sturgeon distributed along the downstream Yichang reach could be affected. This study examined the effects of TGD on the streamflow, sediment load and channel morphology downstream based on in situ measured data. Results showed that, after the impoundment of the TGD, sediment load at the downstream Yichang hydrological station decreased significantly, and the Yichang reach continued to be scoured. The distribution of erosion was uneven, and the scouring mainly occurred in the branching channels. The channel gradient and riverbed roughness increased with the erosion of the river cross section. After more than 10 years of erosion, the riverbed scouring and armouring in the Yichang reach was basically completed, thus we expected that the spawning grounds of Chinese sturgeon could be retain as the riverbed tends to be stable. The findings in this work have implications in the protection of the critically endangered Chinese sturgeon.

Trend and abrupt analysis of Dongting Lake water level and its driving forces using Mann-Kendall approach

In order to quantitatively describe the evolution trend of Dongting Lake water level and its driving forces, the Mann-Kendall approach is used to determine the lake water level and its driving forces, including the discharge of the Yangtze River at Yichang hydrological station, three outlets, and four rivers. The results show that the annual runoff and the runoff from September to October of the Yangtze River, the annual runoff of the three outlets have a significant downward trend, especially after the impoundment of the large reservoirs on the middle and upper reaches of Yangtze River. The Yangtze River discharge has a sudden change during the impoundment period, while the annual runoff and the runoff from September to October of the four rivers showed an insignificant decrease trend. The lake water level at Chenglingji decreased during the impoundment period of the large reservoirs slowed down, especially in September and October, so we can see that the reservoir impoundment is an important factor that decreasing the water level of Dongting Lake.

Hydrological Uncertainty Processor (HUP) with Estimation of the Marginal Distribution by a Gaussian Mixture Model

Uncertainty assessments of hydrological prediction results can reflect additional hydrological information and reveal important hydrological characteristics of river basins, which is of great significance to disaster prevention and reduction. The hydrological uncertainty processor (HUP), which is a key part of the Bayesian forecasting system (BFS), has derived a variety of methods for hydrological uncertainty forecasting. The HUP allows for any form of marginal distributions of hydrological data and does not require a unified estimation structure for the marginal distribution function. The Gaussian mixture model (GMM) is a probability distribution estimation model that can approximate any probability distribution with arbitrary precision. In this paper, the GMM was used to estimate the marginal distribution of observed and modelled data, and this method is called HUP-GMM. The uncertainty of river discharge at the Yichang hydrological station on the main stem of the Yangtze River in China is predicted by the HUP-GMM. The Weibull and Gamma distributions, which are commonly used hydrological probability distributions, are compared to analyse the performance of the GMM. In June, when the measured flow h3 is 13,850 m3/s and the GMM, Gamma and Weibull distributions are used, the prior probabilities are 1.63E-04, 1.05E-04 and 9.50E-05 and the posterior probabilities are 2.57E-04, 1.61E-04 and 1.38E-04, respectively. In September, when the measured flow h3 is 35,400 m3/s and the GMM, Gamma and Weibull distributions are used, the prior probabilities are 5.98E-05, 2.21E-05 and 2.18E-05 and the posterior probabilities are 1.64E-04, 9.15E-05 and 8.43E-05, respectively. The results show that the performance of the uncertainty estimation of the prior and posterior probability distributions in the HUP-GMM has been improved.

Impact of the operation of cascade reservoirs in upper Yangtze River on hydrological variability of the mainstream

Abstract. As the impacts by climate changes and human activities are intensified, variability may occur in river's annual runoff as well as flood and low water characteristics. In order to understand the characteristics of variability in hydrological series, diagnosis and identification must be conducted specific to the variability of hydrological series, i.e., whether there was variability and where the variability began to occur. In this paper, the mainstream of Yangtze River was taken as the object of study. A model was established to simulate the impounding and operation of upstream cascade reservoirs so as to obtain the runoff of downstream hydrological control stations after the regulation by upstream reservoirs in different level years. The Range of Variability Approach was utilized to analyze the impact of the operation of upstream reservoirs on the variability of downstream. The results indicated that the overall hydrologic alterations of Yichang hydrological station in 2010 level year, 2015 level year and the forward level year were 68.4, 72.5 and 74.3 % respectively, belonging to high alteration in all three level years. The runoff series of mainstream hydrological stations presented variability in different degrees, where the runoff series of the four hydrological stations including Xiangjiaba, Gaochang and Wulong belonged to high alteration in the three level years; and the runoff series of Beibei hydrological station in 2010 level year belonged to medium alteration, and high alteration in 2015 level year and the forward level year. The study on the impact of the operation of cascade reservoirs in Upper Yangtze River on hydrological variability of the mainstream had important practical significance on the sustainable utilization of water resources, disaster prevention and mitigation, safe and efficient operation and management of water conservancy projects and stable development of the economic society.

A method for constructing asymmetric pair-copula and its application

ABSTRACTPair-copula has become a hot spot in the research of both theory and application of statistics. Therefore, proper construction of pair-copula is an area worthy of study. Considering the asymmetry of variate dependence in practical applications and the disadvantages of the widely used asymmetric copulas, we propose a method to construct asymmetric pair-copula. In our method, we treat the asymmetric bivariate copula constructed by Liebscher's method as a generator, using this generator to construct asymmetric pair-copula. Also, on the basis of our method, we propose and prove a reference for selecting copula family in the construction. To verify the method, we construct asymmetric copulas and asymmetric pair-copulas using the daily runoff data collected at Yichang hydrological station to describe the extreme drought events of Yangtze River. After comparing the models in some aspects, we accept a model we construct, and the result displays the feasibility and practicality of the method we propose.

Aggravation of north channels' shrinkage and south channels' development in the Yangtze Estuary under dam-induced runoff discharge flattening

Construction of dams on rivers has progressively affected the seasonal variability of runoff discharge, which has consequently produced remarkable impacts on the morphology of estuarine channels. This paper considers four-typical-order bifurcations of the Yangtze Estuary and adopts an ebb partition ratio (defined as the diversion ratio of ebb flow in a given branch divided by the total ebb tidal discharge immediately upstream of the river node where the bifurcation occurs) as a measure of water excavating force in the bifurcation channels. Results show that the seasonal variability of runoff discharge at Datong Hydrological Station (Datong) is flattened, being mainly driven by upstream runoff flattening observed at Yichang Hydrological Station (Yichang) and the tributary rivers. Yearly ebb partition ratios of the channels located to the north and south of the islands present decreasing and increasing trends respectively, and as also do the yearly north and south channel volume of the bifurcations. Yearly ebb partition ratio is proved to be an effective index to represent the water excavating force considering the stability of yearly ebb tidal discharge and its relationship with the channel erosion-deposition. River dams are the driving factors behind the runoff flattening at Datong because of their flattening effects on its main contributors (Yichang and tributary rivers). This flattening significantly helps reduce and enlarge the yearly ebb partition ratios of the north and south channels respectively, and then aggravates the shrinkage and development of the north and south channels separately. Yearly ebb partition ratio of the North Passage (NP) must be enlarged in order for the NP to maintain its function as a shipping channel.

Uncertainties in assessing hydrological drought using streamflow drought index for the upper Yangtze River basin

Drought is an environmental disaster which is frequently and world-widely occurred in recent years. Precisely assessment and prediction of drought is important for water resources planning and management. Sampling uncertainty commonly exists in frequency analysis-based hydrological drought assessment due to the limited length of observed data series. Based on the daily streamflow data of the Yichang hydrological station from 1882 to 2009, the streamflow drought index (SDI) series with 12-month time scale was calculated and the hydrological drought of the upper Yangtze River was assessed. By employing the bootstrap method, the impact of sample size on the sampling uncertainty of the SDI was analyzed. The longer record is used to derive the SDI, the narrower the shifting ranges of the parameters of the streamflow volume probability distribution functions and corresponding interval estimators of SDI are. The upper Yangtze River basin has experienced successive alternation of wet and dry years, and the spring seems to be the driest season within a year. The current difficulty in fighting against increasing droughts in upper Yangtze River basin is upgrading. Considering the possible misjudgment of drought degree results from the sampling uncertainty, attention should be paid to the preparation of drought relief strategies in order to reduce the potential losses.

Temporal Change Analysis Based on Data Characteristics and Nonparametric Test

Based on data characteristics and nonparametric test, a new statistical temporal change analysis approach is proposed. The new approach consists of data characteristics analysis, temporal change analysis (including both change point and trend analysis), and result interpretation. Data characteristics are firstly investigated, especially with respect to the assumptions of independence and normality. Then proper nonparametric methods are chosen based on the detected characteristics of the observed data to analyze change points and monotonous linear trend for each of the segments divided by the change points. To avoid shortcoming of the traditional approach of carrying out the trend analysis before change point analysis, it is proposed in this paper that change point detection be performed before trend analysis. At last, statistical analysis results are interpreted according to the physical mechanism of observations. As a study case, the proposed approach has been carried out on three annual discharge series of the Yangtze River at the Yichang hydrological station. The investigations of data characteristics show that the observed data do not meet the assumptions of being independent and identically Gaussian-distributed. So the nonparametric Pettitt’s test was adopted to detect abrupt changes in the mean levels, followed by trend analysis using the nonparametric Mann-Kendall (MK) test. Results indicate the proposed approach is both reliable and reasonable for the temporal change analysis.

Study on Hydropower Energy and its Future Changes in the Upper Yangtze River Basin under Climate Change

Due to huge hydropower energy in the upper Yangtze River basin, discharge projection is very important for integrated water resources development and management under the background of regional climate change. Projections of river discharge at Yichang hydrological station under three greenhouse gas emission scenarios are studied by two kinds of methods. The projection results show that from 2011 to 2050, annual river discharge at Yichang hydrological station has no obvious trends, but future seasonal discharges have different trends under different greenhouse gas emission scenarios, which increase the difficulties of utilization of hydropower energy in the upper Yangtze River basin.

Impact of the Three Gorges and Gezhouba Reservoirs on Ecohydrological Conditions for Sturgeon in the Yangtze River, China

The Gezhouba Reservoir (GR) and Three Gorges Reservoir (TGR) are the two largest water-storage projects in the middle reach of the Yangtze River. The impoundments of the reservoirs have changed natural flow-regimes in the river. This paper uses the Yichang Hydrological Station as a proxy for water-storage projects along the Yangtze River to assess alterations in river-flow conditions in three separate periods. The periods coincide with the start of water storage in the GR and TGR. The ecohydrological conditions in the river system are assessed based on annual discharge, water level, water temperature, and suspended-sediment concentration. More importantly, the entire analysis is done in relation to the Chinese sturgeon species, which face the danger of extinction in the Yangtze River. Based on the research reported in this paper, the impoundment of the GR and TGR increases downstream average annual water-temperature. In contrast, it decreases downstream average annual runoff, water level, and suspended-sediment concentration. The change of hydrological conditions negatively influences the spawning and hatching conditions of Chinese sturgeon. This change is the key reason that causes the fertilized rate of Chinese sturgeon eggs to decline.

Effects of the Three Gorges Reservoir on the hydrological droughts at the downstream Yichang station during 2003–2011

AbstractSince the Three Gorges Reservoir (TGR) was put into operation in June 2003, the effects of the TGR on downstream hydrology and water resources have become the focus of public attention. This article examines the effects of the TGR on the hydrological droughts at the downstream Yichang hydrological station during 2003–2011. The two‐parameter monthly water balance model was used to generate the monthly discharges at the Yichang station for the period of 2003–2011 to represent the unregulated flow regime and thus to provide a comparison benchmark for the observed flow series at the Yichang station after the operation of the TGR. To provide a reference series for the observed monthly discharge series of the entire study period of 1951–2011, we constructed the naturalized monthly discharge series at the Yichang station by joining the observed monthly discharge at the Yichang station for the period of 1951–2002 and the two‐parameter monthly water balance simulated monthly runoff at the Yichang station for the period of 2003–2011. For both the observed and naturalized monthly discharge series of 1951–2011, the hydrological drought index series were calculated using the standardized streamflow index method. By comparing the drought indices of these two monthly discharge series, we investigated the effects of the TGR on the hydrological droughts at the downstream Yichang station during 2003–2011. The results show that the hydrological droughts at the downstream Yichang station are slightly aggravated by the TGR's initial operation from 2003 to 2011. The river flow reduction at the Yichang station after impoundment of the TGR might account for the downstream drought aggravation. Copyright © 2012 John Wiley & Sons, Ltd.

Uncertainty analysis of hydrological processes based on ARMA-GARCH model

Uncertainty analysis and risk analysis are two important areas of modern water resource management, in which accurate variance estimation is required. The traditional runoff model is established under the assumption that the variance is a constant or it changes with the seasons. However, hydrological processes in the real world are often heteroscedastic, which can be tested by McLeod-Li test and Engle Lagrange multiplier test. In such cases, the GARCH model of hydrological processes is established in this article. First, the seasonal factors in the sequence are removed. Second, the traditional ARMA model is established. Then, the GARCH model is used to correct the residual. At last, the daily runoff data in 1949–2001 of Yichang Hydrological Station is taken to be an example. The result shows that compared to the traditional ARMA model, the GARCH model has the ability to predict more accurate confidence intervals under the same confidence level.

Impact of the Three Gorges reservoir operation on downstream ecological water requirements

With population increase and economic growth, the flow regime of the Yangtze River has been altered to some extent by human activities, particularly dam construction. Dam-induced alterations in the flow regime of the Yangtze River will unavoidably influence water allocation among different water users and instream ecological water requirements may not be guaranteed during some months, particularly during phases of reservoir storing water. To assess the impacts of the Three Gorges reservoir operation on the downstream minimum instream ecological water requirements, this paper selected the Three Gorges reservoir and Yichang hydrological station below the reservoir as case study sites. On the basis of long-term time series of daily discharge data, the reservoir outflow was simulated under two water storing schemes and the degree to which the downstream minimum ecological flow was satisfied was computed. The results of this paper could provide references for the integrated management of the Yangtze River water resources and the assessment of dam-induced impacts on the Yangtze River ecosystem health.

Seasonal and annual maximum streamflow forecasting using climate information: application to the Three Gorges Dam in the Yangtze River basin, China / Prévision d'écoulements saisonnier et maximum annuel à l'aide d'informations climatiques: application au Barrage des Trois Gorges dans le bassin du Fleuve Yangtze, Chine

This paper explores the potential for seasonal prediction of hydrological variables that are potentially useful for reservoir operation of the Three Gorges Dam, China. The seasonal flow of the primary inflow season and the peak annual flow are investigated at Yichang hydrological station, a proxy for inflows to the Three Gorges Dam. Building on literature and diagnostic results, a prediction model is constructed using sea-surface temperatures and upland snow cover available one season ahead of the prediction period. A hierarchical Bayesian approach is used to estimate uncertainty in the parameters of the prediction model and to propagate these uncertainties to the predictand. The results show skill for both the seasonal flow and the peak annual flow. The peak annual flow model is then used to estimate a design flood (50-year flood or 2% exceedence probability) on a year-to-year basis. The results demonstrate the inter-annual variability in flood risk. The predictability of both the seasonal total inflow and the peak annual flow (or a design flood volume) offers potential for adaptive management of the Three Gorges Dam reservoir through modification of the operating policy in accordance with the year-to-year changes in these variables.

Climate teleconnections to Yangtze river seasonal streamflow at the Three Gorges Dam, China

AbstractIn this study, we identify climatic influences on summer monsoon inflow to the Three Gorges Dam (TGD) in the Yangtze River Basin and use indices of these influences to predict streamflow one season ahead. Summer monsoon streamflow at Yichang hydrological station (YHS) was analyzed for the period 1882–2003. Statistical analysis was used to develop a predictive model for summer streamflow using preceding climate variables. Linear correlation maps were constructed using 3‐month ahead climate fields to identify regions that exhibit teleconnections with streamflow at Yichang. The analysis revealed regions in the eastern Indian and western Pacific Oceans that influence YHS streamflow. These regions and variables are consistent with those identified by previous studies of regional rainfall. In addition, snow cover in the Yangtze upland region provides predictive skill, likely due to snowmelt contributions to streamflow. A regression model for prediction using these indices provides a prediction R2 greater than 0.5, which is robust under the ‘leave one out’ cross‐validation. A skillful prediction can provide guidance for water management in the Yangtze River Basin, e.g. the Three Gorges Dam and future projects for South‐to‐North water transfer. Copyright © 2006 Royal Meteorological Society

Analysis on river sediment changes of the upper reaches of Yantze River

The sediment load and river sedimentation of the upper reaches of Yangtze River has been undergoing constant changes as complex landform, large mountain area and plentiful precipitation make the drainage area of Yangtze River very vulnerable to water erosion and gravity erosion. Through analyzing the hydrological and sediment load statistics recorded by major hydrological stations along Yangtze River since 1950s, and editing the accumulation graph of annual runoff volume and annual sediment load, we find out that the suspended-sediment of Yangtze river has been decreasing year by year in Wulong Hydrological Station on Wujiang River. Beibei Hydrological Station on Jialingjiang River, Lijiawan Hydrological Station on Tuojiang River and Gaochang Hydrological Station on Minjiang River, Yichang Hydrological Station, Cuntan Hydrological Station along Yangtze River mainstream share the same experience too. But the statistics obtained at Pingshan Hydrological Station on Jinshajiang River shows the sediment load there has increased. Taking ecological construction, hydraulic engineering construction and precipitation changes into consideration, the thesis analyses the causes for the sediment load decrease of Jialingjiang River, Tuojiang River, Minjiang River and Wujiang River and provides us both scientific foundation for further study of river sediment changes of the upper reaches of Yangtze River, and measures to control river sedimentation.

Trend test and change-point detection for the annual discharge series of the Yangtze River at the Yichang hydrological station / Test de tendance et détection de rupture appliqués aux séries de débit annuel du fleuve Yangtze à la station hydrologique de Yichang

The trend test and change-point analysis have been carried out on several annual discharge series of the Yangtze River at the Yichang hydrological station, including the discharge series of the annual maximum, annual minimum and annual mean during the period 1882–2001. The results of both the Mann-Kendall and Spearman’s rho trend tests show that, at the 5% significance level, the annual maximum flood series did not have any statistically significant trend, but the annual minimum flow series and the annual mean discharge series exhibited a sign of decreasing trend. For single change-point detection, a Bayesian model was established to study the abrupt change in the mean levels of the time series. Given the observed hydrological data, the Bayesian model can estimate the posterior probability distribution of each change-point location by using the Monte Carlo Markov Chain (MCMC) sampling method. The results of the Bayesian model show that, during the past 120 years, the mean levels of both the annual minimum discharge series and the annual mean discharge series have decreased by 8% and 6% respectively. Further analysis suggested that, for the annual minimum discharge series and the annual mean discharge series, both the trend term and the abrupt change term are very closely related and very hard to distinguish from each other.