scholarly journals Frequency Analysis of the Nonstationary Annual Runoff Series Using the Mechanism-Based Reconstruction Method

Water ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 76
Author(s):  
Shi Li ◽  
Yi Qin
Keyword(s):  
River Basin ◽  
Frequency Analysis ◽  
Annual Runoff ◽  
Statistical Characteristics ◽  
Reconstruction Method ◽  
Runoff Series ◽  
Design Values ◽  
Northern Shaanxi ◽  
Nonstationary Frequency ◽  
Nonstationary Conditions

Due to climate change and human activities, the statistical characteristics of annual runoff series of many rivers around the world exhibit complex nonstationary changes, which seriously impact the frequency analysis of annual runoff and are thus becoming a hotspot of research. A variety of nonstationary frequency analysis methods has been proposed by many scholars, but their reliability and accuracy in practical application are still controversial. The recently proposed Mechanism-based Reconstruction (Me-RS) method is a method to deal with nonstationary changes in hydrological series, which solves the frequency analysis problem of the nonstationary hydrological series by transforming nonstationary series into stationary Me-RS series. Based on the Me-RS method, a calculation method of design annual runoff under the nonstationary conditions is proposed in this paper and applied to the Jialu River Basin (JRB) in northern Shaanxi, China. From the aspects of rationality and uncertainty, the calculated design value of annual runoff is analyzed and evaluated. Then, compared with the design values calculated by traditional frequency analysis method regardless of whether the sample series is stationary, the correctness of the Me-RS theory and its application reliability is demonstrated. The results show that calculation of design annual runoff based on the Me-RS method is not only scientific in theory, but also the obtained design values are relatively consistent with the characteristics of the river basin, and the uncertainty is obviously smaller. Therefore, the Me-RS provides an effective tool for annual runoff frequency analysis under nonstationary conditions.

scholarly journals Spring flood frequency analysis in the Southern Buh River Basin, Ukraine

2021 ◽  
Vol 30 (2) ◽  
pp. 250-260
Author(s):  
Liudmyla O. Gorbachova ◽  
Viktoria S. Prykhodkina ◽  
Borys F. Khrystiuk
Keyword(s):  
Time Series ◽  
River Basin ◽  
Frequency Analysis ◽  
Practical Importance ◽  
Statistical Characteristics ◽  
Flood Frequency Analysis ◽  
Spring Flood ◽  
Cyclical Fluctuations ◽  
Pearson Type ◽  
Maximal Runoff

The river floods are among the most dangerous natural disasters in the world. Each year, the spring floods cause the significant material damage in the different countries, including Ukraine. Knowledge of trends in such floods, as well as their probabilistic forecast, is of great scientific and practical importance. In last decades, the decreasing phase of cyclical fluctuations of the maximum runoff of spring floods has been observed on the plain rivers of Ukraine, including the Southern Bug River. In addition, there is an increase in air temperature. So, the actual task is the determine the modern probable maximum discharges estimates of spring floods in the Southern Buh River Basin as well as their comparison with the estimates that were computed earlier. It gives an opportunity to reveal possible changes of the statistical characteristics and values of the probable maximum discharges, to analyze and to discuss the reasons for these changes. For the investigation, we used the time series of the maximum discharges of spring floods for 21 gauging stations in the Southern Buh River Basin since the beginning of the observations and till 2015. The method of the regression on the variable that is based on the data of analogues rivers was used to bringing up the duration of the time series and restoration of the gaps. In the study, the hydro-genetic methods for estimation of the homogeneity and stationarity of hydrological series, namely the mass curve, the residual mass curve and the combined graphs. The distributions of Kritskyi & Menkel and Pearson type III for the frequency analysis were used. It has been shown in this study that the maximum discharges of spring floods of time series are quasi-homogeneous and quasi-stationary. It is explained the presence in the observation series of only increasing and decreasing phases of cyclical fluctuations, their considerable duration, as well as the significant variability of the maximal flow. The series of maximal runoff of spring floods are very asymmetric, which significantly complicates the selection of analytical distribution curves. The updated current parameters of the maximal spring flood runoff have not changed significantly. It can be assumed that such characteristics have already become stable over time, as the series of maximal runoff of spring floods already have phases of increasing and decreasing of long-term cyclic fluctuations.

Recent Intensified Runoff Variability in the Hailar River Basin during the Past Two Centuries

2020 ◽  
Vol 21 (10) ◽  
pp. 2257-2273
Author(s):  
Junxia Li ◽  
Xueping Bai ◽  
Yuting Jin ◽  
Fangbo Song ◽  
Zhenju Chen ◽  
...  
Keyword(s):  
River Basin ◽  
Northeast China ◽  
Southern Oscillation ◽  
Annual Runoff ◽  
The Past ◽  
Increased Risk ◽  
Runoff Series ◽  
Tree Ring Data ◽  
Natural Land ◽  
Runoff Variability

AbstractUsing tree-ring data of Pinus sylvestris var. mongolica from the Hulun Buir region in northeast China, 12 annual runoff series of the Hailar River spanning the past 202–216 years were established for the first time; these included 11 branches and one for the entire basin. These reconstructions, which could explain 29.4%–52.7% of the total variance for the measured runoffs during 1956–2006, performed well in statistical verification tests. In the whole basin’s reconstruction of 212 years, 34 extreme drought years (16.0%) and 41 extreme pluvial years (19.3%) were identified; 4 of the 10 most extreme years occurred after 1980. The consistent cycle and correlation revealed that the Hailar runoff had a teleconnection with the El Niño–Southern Oscillation (ENSO). The sharply increasing variance at the end of the reconstruction, accompanied by the increasing intensity of short cycles (4–8 years), indicated that runoff variability in the Hailar River basin has enhanced in the late twentieth century. This is verified by the drastic fluctuations in water level and area of rivers and lakes, and the frequent shift of natural land cover types in the Hulun Buir area in recent decades. The intensified runoff variability can be connected with the concurrently enhanced ENSO activity. Our study is the first to identify the intensification of recent runoff variability in the semiarid to arid region in northeast China from a long-term perspective. With projected enhancement of ENSO activity, the Hailar River basin will face the increased risk of extreme hydrological events.

Nonstationary frequency analysis for annual runoff and sediment load of the Wujiang River

2020 ◽  
Author(s):  
Rongrong Li
Keyword(s):  
River Basin ◽  
Human Activities ◽  
Sediment Load ◽  
Heavy Rain ◽  
Annual Runoff ◽  
Statistical Characteristics ◽  
Explanatory Variables ◽  
Wujiang River ◽  
Before And After ◽  
The Impact

<p>The hydrological series can no longer meet the stationarity hypothesis due to the influence of climate variability and human activities. The process of runoff and sediment load changed significantly under a changing environment. Analyzing the variations of runoff and sediment load and exploring the main influencing causes leading to their changes will be of great help to understand the dynamic process of water and sediment in river basin. Many studies have considered the effects of rainfall and reservoir on the downstream runoff or sediment: the impact of rainfall on runoff or sediment load is normally performed by comparing the statistical characteristics before and after an extreme weather event (e.g. heavy rain of the Yangtze river in 1998); the effect of reservoirs is usually determined by comparing the pre-dam and post-dam frequencies of runoff or sediment load. In this study, the major influencing factors of annual runoff and sediment load in Wujiang River basin were identified firstly based on the results of trend analysis and change-point diagnosis for runoff and sediment load. Then, Generalized Addictive Models in Location, Scale, and Shape (GAMLSS) is used to describe the rainfall and reservoir impacts on nonstationarity of runoff and sediment load, in which, distribution parameters (including the location, scale and shape parameter) are expressed as a function of the explanatory variables. The results show that: (1) runoff and sediment load of Wujiang River decrease with the intensification of climate change and human activities; (2) runoff is mainly affected by rainfall, the operation of cascade reservoirs has critical effect on the sediment load; (3) the correlation between runoff and sediment closely related to the nonstationarity of sediment load, namely, the sediment load change can directly lead to the alteration of dependence between runoff and sediment.</p>

scholarly journals 1845–2016 gridded dataset of monthly precipitation over the upper Adda river basin: a comparison with runoff series

2018 ◽  
Vol 15 ◽  
pp. 173-181 ◽  
Author(s):  
Alice Crespi ◽  
Michele Brunetti ◽  
Maurizio Maugeri ◽  
Roberto Ranzi ◽  
Massimo Tomirotti
Keyword(s):  
River Basin ◽  
Melting Rate ◽  
Annual Runoff ◽  
Monthly Precipitation ◽  
Precipitation Series ◽  
Gridded Dataset ◽  
Runoff Series ◽  
Leave One Out ◽  
Station Density

Abstract. A new high-resolution gridded dataset of 1845–2016 monthly precipitation series for the upper Adda river basin was computed starting from a network of high-quality and homogenised station records covering Adda basin and neighbouring areas and spanning more than two centuries. The long-term signal was reconstructed by a procedure based on the anomaly method and consisting in the superimposition of two fields which were computed independently: 1961–1990 monthly climatologies and gridded anomalies. Model accuracy was evaluated by means of station series reconstruction in leave-one-out approach and monthly relative mean absolute errors were found to range between 14 % in summer and 24 % in winter. Except for the period before the 1870s when station coverage is rather low, reconstruction errors are quite stable. The 1845–2016 monthly areal precipitation series integrated over Adda basin was finally computed. The robustness of this series was evaluated and it was investigated for long-term trend. While no significant trend emerged for precipitation, the analysis performed on 1845–2016 annual runoff values recorded at Lake Como outlet highlighted a negative trend. Runoff decrease is supposed to be mostly due to an increasing role of evapotranspiration linked to temperature increase, which is only partially compensated by the increase in glacier melting rate. In order to test the applicability of the gridded database for the reconstruction of extreme past events, the episode with the highest precipitation in Adda basin series (November 2002) was considered and the corresponding gridded fields of monthly anomalies and precipitation values were evaluated both with actual station density and with station densities corresponding to 1922 and 1882. Even considering 1882 station density, the main spatial patterns are well depicted proving the suitability of anomaly method to deal also with sparse station networks.

scholarly journals A Cross-Reconstruction Method for Step-Changed Runoff Series to Implement Frequency Analysis under Changing Environment

2019 ◽  
Vol 16 (22) ◽  
pp. 4345 ◽  
Author(s):  
Jiantao Yang ◽  
Hongbo Zhang ◽  
Chongfeng Ren ◽  
Zhengnian Nan ◽  
Xiaowei Wei ◽  
...  
Keyword(s):  
Frequency Analysis ◽  
Measured Data ◽  
Small Sample ◽  
Western China ◽  
Reconstruction Method ◽  
Changing Environments ◽  
Runoff Series ◽  
Data Capacity ◽  
The Cross ◽  
Data Expansion

The stationarity of observed hydrological series has been broken or destroyed in many areas worldwide due to changing environments, causing hydrologic designs under stationarity assumption to be questioned and placing designed projects under threat. This paper proposed a data expansion approach—namely, the cross-reconstruction (CR) method—for frequency analysis for a step-changed runoff series combined with the empirical mode decomposition (EMD) method. The purpose is to expand the small data on each step to meet the requirements of data capacity for frequency analysis and to provide more reliable statistics within a stepped runoff series. Taking runoff records at three gauges in western China as examples, the results showed that the cross-reconstruction method has the advantage of data expansion of the small sample runoff data, and the expanded runoff data at steps can meet the data capacity requirements for frequency analysis. In addition, the comparison of the expanded and measured data at steps indicated that the expanded data can demonstrate the statistics closer to the potential data population, rather than just reflecting the measured data. Therefore, it is considered that the CR method ought to be available in frequency analysis for step-changed records, can be used as a tool to construct the hydrological probability distribution under different levels of changing environments (at different steps) through data expansion, and can further assist policy-making in water resources management in the future.

ESTIMATION OF THE T-YEAR SPECIFIC DISCHARGE USING THE REGIONALISED SKEWNESS COEFFICIENT OF THE LOG-PEARSON TYPE III DISTRIBUTION

2020 ◽  
Author(s):  
Jakub Mészáros ◽  
◽  
Pavol Miklánek ◽  
Pavla Pekárová ◽  
◽  
...  
Keyword(s):  
River Basin ◽  
Type Iii ◽  
River Region ◽  
Pearson Type ◽  
Skewness Coefficient ◽  
Distribution Parameters ◽  
Design Values ◽  
Specific Discharge ◽  
Morava River ◽  
Pearson Type Iii Distribution

In this paper the results are presented of estimation of T-year specific discharge of several streams in two regions in Slovakia. The Qmax time series used in the study were observed at water gauges from lowland Slovak part of the Morava River basin, and from the mountainous Belá River basin. For estimating the design values, we have studied the use of only one type of probability distribution, namely the Log-Pearson Type III Distribution (LP3 distribution). The use of only one type of distribution brings several benefits, e.g. possibility of the regionalization of the distribution parameters (in this study skew coefficient). In the first step the design values of the specific discharge series qmax (with historical data) were estimated and regional skew coefficients Gr of the LP3 distribution were computed. Regional skewness coefficient Gr was estimated to be 0.38 in the Morava River region, and 0.73 in the Belá River region. In many cases the estimate of the 1000-year specific discharge is two times higher than the value of the 100-year specific discharge. Then we have derived the empirical relations between station skew coefficient G and the elevation of the water gauge. In the second step we have derived the empirical relationships between 1000-years specific discharge q1000 and the elevation of the water gauge for both regions separately. The derived empirical regional equations can be used to estimate the 1000-years specific discharge of other streams in the region.

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