Research on runoff variations based on wavelet analysis and wavelet neural network model： A case study of the Heihe River drainage basin （1944-2005）

The Heihe River drainage basin is one of the endangered ecological regions of China. The shortage of water resources is the bottleneck, which constrains the sustainable development of the region. Many scholars in China have done researches concerning this problem. Based on previous researches, this paper analyzed characteristics, tendencies, and causes of annual runoff variations in the Yingluo Gorge （1944-2005） and the Zhengyi Gorge （1954-2005）, which are the boundaries of the upper reaches, the middle reaches, and the lower reaches of the Heihe River drainage basin, by wavelet analysis, wavelet neural network model, and GIS spatial analysis. The results show that： （1） annual runoff variations of the Yingluo Gorge have principal periods of 7 years and 25 years, and its increasing rate is 1.04 m^3/s.10y; （2） annual runoff variations of the Zhengyi Gorge have principal periods of 6 years and 27 years, and its decreasing rate is 2.25 m^3/s.10y; （3） prediction results show that： during 2006-2015, annual runoff variations of the Yingluo and Zhengyi gorges have ascending tendencies, and the increasing rates are respectively 2.04 m^3/s.10y and 1.61 m^3/s.10y; （4） the increase of annual runoff in the Yingluo Gorge has causal relationship with increased temperature and precipitation in the upper reaches, and the decrease of annual runoff in the Zhengyi Gorge in the past decades was mainly caused by the increased human consumption of water resources in the middle researches. The study results will provide scientific basis for making rational use and allocation schemes of water resources in the Heihe River drainage basin.

基于Wavelet-Anfis模型的陈家湾水库长期径流预测

针对径流序列特性变化复杂且难以预测的问题，提出了基于WaveletAntis的径流预测模型。首先对长期径流序列进行拟舍得到原始信号，通过Sym8小波对该信号进行尺度为4的分解，得到对应的低频信号A。和高频信号D1～D4，利用Anfis对这些分解信号逐步训练以确定最佳模型，从而预测出低、高频信号预测期的序列值，最后将各预测序列重构回原尺度生成径流预测值。将该方法应用于陈家湾水库年径流序列中，并与直接Antis预测结果进行对比。结果表明，Wavelet—Anfis模型预测值的相对误差较小，且具有较快的收敛速度，既有效又准确。

Long-term Trend and Fractal of Annual Runoff Process in Mainstream of Tarim River

Based on the time series data from the Aral hydrological station for the period of 1958-2005,the paper re-veals the long-term trend and fractal of the annual runoff process in the mainstream of the Tarim River by using the wavelet analysis method and the fractal theory.The main conclusions are as follows:1)From a large time scale point of view,i.e.the time scale of 16(24)years,the annual runoff basically shows a slightly decreasing trend as a whole from 1958 to 2005.If the time scale is reduced to 8(23)or 4(22)years,the annual runoff still displays the basic trend as the large time scale,but it has fluctuated more obviously during the period.2)The correlation dimension for the annual runoff process is 3.4307,non-integral,which indicates that the process has both fractal and chaotic characteris-tics.The correlation dimension is above 3,which means that at least four independent variables are needed to describe the dynamics of the annual runoff process.3)The Hurst exponent for the first period(1958-1973)is 0.5036,which equals 0.5 approximately and indicates that the annual runoff process is in chaos.The Hurst exponents for the second(1974-1989)and third(1990-2005)periods are both greater than 0.50,which indicate that the annual runoff process showed a long-enduring characteristic in the two periods.The Hurst exponent for the period from 1990 to 2005 indi-cates that the annual runoff will show a slightly increasing trend in the 16 years after 2005.

Human impacts on runoff regime of middle and lower Yellow River

In this study, the 54-year （1950 to 2003） monthly runoff series from February, April, August, and November, as well as the annual runoff series, measured at both Huayuankou and Lijin hydrological stations were chosen as representative data, and the continuous wavelet transform （CWT） was applied to analyze the impacts of human activities on the runoff regime of the middle and lower Yellow River. A point of change in 1970 was first determined, and the observed series before 1970 were considered natural runoff while those after 1970 were restored according to linear trends. Then, the CWT was applied to both the observed and restored runoff series to reveal their variations at multi-temporal scales, including the five temporal ranges of 1-4, 6-8, 9-12, 16-22, and 22-30 years, and the trend at the temporal scale of 54 years. These analysis results are compared and discussed in detail. In conclusion, because of the impacts of human activities, there have been significant changes in the runoff regime in the middle and lower Yellow River since 1970. The decaying tendency of annual runoff has become more pronounced, and the inner-annual distribution of runoff has changed, but human activities have had little impact on the periodic characteristics of runoff.

Simulation and prediction of monthly accumulated runoff,based on several neural network models under poor data availability

Most previous research on areas with abundant rainfall shows that simulations using rainfall-runoff modes have a very high prediction accuracy and applicability when using a back-propagation(BP), feed-forward, multilayer perceptron artificial neural network(ANN). However, in runoff areas with relatively low rainfall or a dry climate, more studies are needed. In these areas—of which oasis-plain areas are a particularly good example—the existence and development of runoff depends largely on that which is generated from alpine regions. Quantitative analysis of the uncertainty of runoff simulation under climate change is the key to improving the utilization and management of water resources in arid areas. Therefore, in this context, three kinds of BP feed-forward, three-layer ANNs with similar structure were chosen as models in this paper.Taking the oasis–plain region traverse by the Qira River Basin in Xinjiang, China, as the research area, the monthly accumulated runoff of the Qira River in the next month was simulated and predicted. The results showed that the training precision of a compact wavelet neural network is low; but from the forecasting results, it could be concluded that the training algorithm can better reflect the whole law of samples. The traditional artificial neural network(TANN) model and radial basis-function neural network(RBFNN) model showed higher accuracy in the training and prediction stage. However, the TANN model, more sensitive to the selection of input variables, requires a large number of numerical simulations to determine the appropriate input variables and the number of hidden-layer neurons. Hence, The RBFNN model is more suitable for the study of such problems. And it can be extended to other similar research arid-oasis areas on the southern edge of the Kunlun Mountains and provides a reference for sustainable water-resource management of arid-oasis areas.

Runoff Characteristics of the Nen River Basin and its Cause

Based on annual runoff data collected from several hydrological stations in the Nen River Basin from 1956 to 2004,the cumulative filter method,Mann-Kendall method and Morlet wavelet analysis were used to analyze variations in the characteristics and factors influencing runoff.Specifically,the general characteristics list as:The distribution of runoff was found to be uneven within a year,and the annual variation showed an overall decreasing trend.The abrupt change points of runoff were found to be in the early 1960s,middle 1980s and late 1990s.Multiple time scales analysis revealed three time-scale cycles,a long-term cycle of about 20-35 years with a scale center of 25 years,another cycle of about 8-15 years with a scale center of 11 years and a short-term cycle of about 5 years.Based on the Morlet wavelet transform coefficients figure of the 25-year time scale,it is preliminarily estimated that the Nen River Basin will enter a high flow period in 2013.The results obtained using various methods were consistent with each other.The physical causes of the results were also analyzed to confirm their accuracy.

Association of North Atlantic Oscillations with Aksu River runoff in China

The relationship between North Atlantic Oscillations （NAO） and Aksu River Runoff （ARR） was investigated by using the wavelet transform （WT）, cross wavelet transform （CWT）, correlation and linear trend analyses, and abrupt change test. The main results are as follows the interannual/decadal variation and period analyses of ARR and NAO reveal that the both were close correlated each other; the CWT indicates that the correlation was good between ARR and NAO at all periods in the 1990s, because the significant correlation areas mainly concentrated in the 1990s; the variations in the trend strength of ARR and NAO were consistent; the abrupt change of NAO was also temporally consistent with that of ARR, which exerted impact on the Aksu River Basin （ARB） climate and then the ARR through atmospheric circulation variation.

Analysis of characteristics of time-frequency correlations between runoff,tidal range and salinity in the Changjiang Estuary

Power spectrum and cross-wavelet transform analysis was adopted to study the time-frequency characteristics and multiscale correlations between runoff,tidal range and salinity in the Changjiang Estuary based on the runoff data collected at the Datong Station,the tidal range measured at the Baozhen Station,and the salinity at the Baogang Station from 2008 to 2009.The variations of the salinity showed significant periodicity at scales of 2-3,7-8,14-15 and 26-30 d.The correlation between the salinity and the runoff and the tidal range were found to be significantly related to shock at scales of 5-7,14-15,26-30 d and 0.5 a.The correlation between the runoff and the salinity was mainly in the same phase,while the correlation between the tidal range and the salinity was in the antiphase.Different frequency bands were related to different degrees,and their relevance increased as the resonance frequency decreased.In addition,changes of the seasonal runoff were obvious.Specifically,a point of discontinuity was reached in early June with a cycle of 7-8 d,which coincided with the periodicity of plum rains in the Changjiang-Huaihe region.High-frequency changes （8-16 d period） of the salinity corresponded to the time domain in January-April 2008,February-April 2009 and October-December 2009 and exhibited an approximately 0.5 a （184 d） long frequency oscillation.Short-period changes were found to be stronger than long-period changes.Cross-wavelet transforms for the salinity,the runoff and the tidal range revealed local features in the time domain,while the significant levels of different periodic oscillations were observed in the frequency domain.The correlation characteristics of the salinity and the runoff were significant in the 80-90 d frequency domain,indicating that the major impact of the runoff on the salinity was reflected in seasonal changes.The tidal range on the small scale of 14-15 and 30-32 d was more obvious than the runoff.

疏勒河流域径流量和输沙量变化规律

[目的]探索疏勒河流域水沙变化特性,可为国家实施西部生态安全战略提供科学支撑。[方法]基于疏勒河流域昌马堡、潘家庄、党城湾3个水文站的实测径流量和输沙量序列资料,运用滑动平均、Mann-Kendall突变趋势检验和小波分析法等方法,分析了疏勒河流域径流量和输沙量变化规律。[结果]疏勒河流域年径流量和年输沙量均呈递增趋势,且输沙量增大趋势大于径流量,昌马堡、潘家庄、党城湾3个水文站径流量分别在1999年、2016年、1982年发生突变,昌马堡和潘家庄年输沙量突变均发生在1998年,党城湾输沙量没有突变;疏勒河流域3个代表站的径流量和输沙量都呈现出多时间尺度的演化特征,昌马堡径流量主周期为58 a,31 a,14 a,9 a和5 a,输沙量主周期为48 a,23 a,14 a,7 a和5 a,潘家庄径流量主周期为59 a,32 a,14 a,输沙量主周期为37 a,14 a,8 a和5 a,党城湾径流量主周期为42 a和5 a,输沙量主周期为16 a和8 a。[结论]疏勒河流域水沙总体呈递增趋势,且存在明显的周期变化,除党城湾的输沙量没有突变发生以外,其余站点水沙均有突变发生,同一水文站输沙量的突变的发生滞后于径流量的突变。

Synchronism of runoff response to climate change in Kaidu River Basin in Xinjiang,Northwest China

The runoff in alpine river basins where the runoff is formed in nearby mountainous areas is mainly affected by temperature and precipitation. Based on observed annual mean temperature, annual precipitation, and runoff time-series datasets during 1958-2012 within the Kaidu River Basin, the synchronism of runoff response to climate change was analyzed and iden- tified by applying several classic methods, including standardization methods, Kendall＇s W test, the sequential version of the Mann-Kendall test, wavelet power spectrum analysis, and the rescaled range （R/S） approach. The concordance of the nonlinear trend variations of the annual mean temperature, annual precipitation, and runoff was tested significantly at the 0.05 level by Kendall＇s W method. The sequential version of the Mann-Kendall test revealed that abrupt changes in annual runoff were synchronous with those of annual mean temperature. The periodic characteristics of annual runoff were mainly consistent with annual precipitation, having synchronous 3-year significant periods and the same 6-year, 10-year, and 38-year quasi-periodicities. While the periodic characteristics of annual runoff in the Kaidu River Basin tracked well with those of annual precipitation, the abrupt changes in annual runoff were synchronous with the annual mean temperature, which directly drives glacier- and snow-melt processes. R/S analysis indicated that the annual mean temperature, annual precipitation, and runoff will continue to increase and remain synchronously persistent in the future. This work can improve the understanding of runoff response to regional climate change to provide a viable reference in the management of water resources in the Kaidu River Basin, a regional sustainable socio-economie development.

Climate Change and Its Effects on Runoff in the North of Tianshan,Xinjiang

[Objective] The aim was to study climate changes in northern Tianshan in Xinjiang and its influences on runoff. [Methed] Based on the runoff data for 54 years of Kenswatt station on Manas River and the climate date of 16 meteorological stations from 1957 to 2007 in the north of Tian- shan in Xinjiang, the climate change and temporal series of the annual runoff were studied by use of nonparametric test, wavelet analysis, R/S analysis and periodic trend superposition model. [ Result] The temperature, precipitation and annual runoff of Manas River increased significantly. The Hurst coefficients of both climate factors and the annual runoff were bigger than 0.5, which indicated that they would still keep an increasing trend. Temperature from 1957 to 1959 was low, precipitation was much, belonging to low temperature and more rain period. 1960s and 1970s were low temperature and less rain period. Temperature in 1980s was close to average value and precipitation was little. Since 1990s, it entered into high temperature and less rain period and was significant during 2000 and 2007. The temperature and precipitation changed in 1995 and 1996. Tempera- ture was＇significant in 11 and 22 years. Precipitation had 5, 8, 14 and 22 years of main cycle. The annual runoff and climate factors in Manasi River were increasing in different times. The annual runoff was related to climate factors, and temperature was closer to annual runoff than precipitation. [ Conclusion] The study provided theoretical basis for the reasonable configuration, ecological protection and agricultural production of water re- sources in north Tianshan in Xinjiang.

石羊河下游蔡旗站径流变化趋势及影响因素

石羊河下游是资源性缺水最严重的地区,水资源对当地社会经济发展的约束作用十分显著。以石羊河下游蔡旗水文站1956—2020年径流序列数据为基础,采用滑动t检验法、累计距平法和M-K突变检验法分析蔡旗水文站径流量变化趋势、突变年份,利用Morlet小波法分析径流量的周期变化,利用双累计曲线法和相关分析法对径流量变化的影响因素进行探究。结果表明:(1)1956—2020年蔡旗水文站年径流量总体呈先减少后增加的趋势,春夏秋三季的径流量亦呈先减少后增加的趋势,冬季则呈波动减少趋势。(2)蔡旗水文站径流量以46 a为第一主周期,存在于整个研究期,丰枯波动变化明显。(3)蔡旗水文站径流量于1972年、2010年发生了两次明显突变,第一次突变后径流量明显减小,第二次突变后径流量明显增加。(4)在研究区气候不断变化的背景下,土地利用变化、跨流域调水引水、产业结构与种植业结构调整、灌区节水等人类活动是引起蔡旗水文站径流量变化的主要原因。研究结果可为流域管理部门合理制定水资源分配及调用方案提供科学依据。

黄河源区汛期降水径流序列多尺度小波分析

基于黄河源区15个地面站点日降水数据、唐乃亥水文站逐日径流数据以及小波分析方法,分析了黄河源区1961—2020年汛期降水和径流的周期规律、变化趋势及相关关系。结果表明,1)黄河源区近60 a汛期降水、径流均存在多时间尺度的变化特征,且不同时间尺度汛期降水、径流丰枯变化趋势均不同;2)汛期降水、径流序列均具有63 a左右、35 a左右特征时间尺度的主周期,两个时间尺度下的平均周期分别为41、25 a左右,汛期降水、汛期径流具有一定的正相关性;3)在63 a特征时间尺度可预测2020年之后未来5~10 a内黄河源区汛期降水、径流整体均呈减小趋势。

秦岭北麓典型流域径流对气候和土地利用变化的响应——以灞河流域为例

气候和土地利用变化对径流变化的影响显著,为探究两者影响下秦岭北麓典型城市流域径流的变化特征及响应机制,选择灞河流域为研究对象,根据灞河流域1960-2018年水文气象数据和1985-2018年土地利用,采用滑动T检验、TFPWMK秩次检验、连续小波变换(CWT)、交叉小波变换(XWT)、小波相干分析(WTC)等方法对流域水文、气象及下垫面要素的变化特征及流域径流与气象要素的共振周期、相关性与时滞性进行了研究;并结合SWAT模型,通过设置多种变化情景探明流域径流对气候和土地利用变化的响应机制。结果表明:1)1960-2018年灞河流域径流量呈显著下降趋势,1985-2018年灞河流域城镇建设用地增加了近3倍,耕地面积呈减少趋势;2)径流与气象因子在时频域中均存在不同尺度的共振周期和时滞效应,降水和径流在高能区存在5个显著的共振周期,气温和径流在高能区存在3个显著的共振周期,且径流滞后于气象因子的变化;3)年均径流量与降水量呈正相关,与气温呈负相关,流域径流变化主要由降水主导,且在降水增加情景下,径流对降水变化的敏感性高于降水减少情景;耕地全部转化为林地会导致年径流量减少2.58%,草地全部转化为林地会使年径流量增加0.822%,耕地全部转为城镇建设用地使年径流量增加40.8%;4)气候和土地利用变化共同作用下,灞河流域径流变幅为-0.870 m^(3)∙s^(-1),其中气候变化引起的径流量变幅为-1.04 m^(3)∙s^(-1),土地利用变化引起的变幅为0.170 m^(3)∙s^(-1),相比土地利用变化,气候变化对于灞河流域径流变化的影响更显著。

长江源区径流变化及其影响因素探讨

长江源区对气候变化的响应较为敏感,其河川径流也随之产生了明显的变化。根据长江源区直门达水文站及长江源区5个气象站1960—2022年实测水文气象资料,分析长江源区年径流和季节性径流变化规律。利用相关分析、交叉小波变换及主成分分析法,分析径流变化与主要气象要素之间的关联性。研究结果表明,近63 a来直门达站年径流呈现显著上升的趋势,尤其是近20 a径流大幅度增加。1960—2000年期间,长江源区各季节性径流变化趋势较为平稳。2000—2022年期间,各季节性径流均呈现出增加的态势并延续至今。对直门达站径流影响最为密切的气象要素主要为降水、气温、相对湿度等。

多极小波包变换与改进浣熊算法优化的混合核极限学习机径流预测

为提高日径流多步预测精度,减少模型计算规模,同时提升浣熊优化(COA)算法和混合核极限学习机(HKELM)性能,提出多极小波包变换(MWPT)-改进COA算法(ICOA)-HKELM日径流时间序列预测模型。首先,利用MWPT将日径流时序数据分解为1个低频分量和2个高频分量,并构建局部高斯径向基核函数和全局多项式核函数相混合的HKELM;其次,简要介绍COA算法原理,基于Circle映射等策略对COA进行改进,提出ICOA算法,通过8个典型函数对ICOA算法进行仿真验证,并与基本COA算法、鲸鱼优化算法(WOA)、灰狼优化算法(GWO)作对比,旨在验证ICOA算法的优化性能;最后,利用ICOA优化HKELM超参数(正则化参数、核参数、权重系数),建立MWPT-ICOA-HKELM模型,并构建MWPT-COA-HKELM、MWPT-WOA-HKELM、MWPT-GWO-HKELM、小波包变换(WPT)-ICOA-HKELM、小波变换(WT)-ICOA-HKELM、MWPT-ICOA-BP模型作对比分析,通过云南省景东、把边水文站2016-2020年日径流时间序列多步预测实例对各模型进行验证。结果表明:(1)ICOA具有较好的改进效果,仿真精度优于COA、WOA、GWO算法。(2)MWPT-ICOA-HKELM模型预测效果优于其他对比模型,其对实例单步预测效果“最好”,超前3步和超前5步“较好”,超前7步“较差”,预测精度随预测步长的增加而降低。(3)利用ICOA优化HKELM超参数,可显著提高HKELM预测性能,超参数优化效果优于COA、WOA、GWO算法。

1960—2020年黄河、长江、珠江入海水沙通量演变特征

[目的]基于动态更新数据综合对比中国三大河流入海水沙通量的特征,为流域开发和管理提供依据。[方法]收集黄河(利津站)、长江(大通站)、珠江(高要站、石角站、博罗站)5个水文控制站1960—2020年实测数据,采用滑动平均法、Pettitt检验法、双累积曲线法以及小波变换分别对水沙通量的趋势性、变异性、周期性特征进行分析,采用交叉小波变换和小波相干谱探究径流量和泥沙量的共振周期与相干性。[结果]近60a黄河、长江、珠江入海水沙通量均发生了明显变化,黄河径流量和泥沙量在1986年突变减少,泥沙量在1997年二次突变减少;长江和珠江入海径流量未发生变异,泥沙量分别于1992,1999年突变减少。这三大河流入海水沙具有显著的年际和年代际周期特征,年代际共同演化周期分别集中于1980年以前、1990年以前和2000年以前。年际共同演化周期为5a,“丰—枯”转换频繁。交叉小波分析结果显示,黄河、长江和珠江的入海径流量和泥沙量在1965—1975年具有显著的1~3a的共振周期,以正相位演变为主。[结论]中国三大河流入海水沙具有显著的趋势性、变异性和周期性特征,可以据此进行的流域开发和管理更有效。

邯郸多个水文站近60年径流量变化特征分析

漳卫河水系和子牙河水系是邯郸河流的重要组成部分,为探究其径流量的变化特征,选取刘家庄、观台、东武仕、木鼻四个水文站近60 a实测径流量为研究对象,采用线性回归法、Mann-Kendall检验法、Morlet小波分析法从趋势性、突变性、周期性的角度分别对其变化特征进行分析,结果表明:(1)在1956-2016年间,刘家庄、观台、东武仕三站的年径流量均呈现出下降的趋势,而木鼻站的年径流量呈现出上升趋势。(2)刘家庄、观台、木鼻站年径流量序列的突变年份分别为1972年、1978年、1956年和2002年,东武仕站年径流量序列不存在突变年份。(3)刘家庄站和东武仕站年径流量序列周期大致为14 a,观台站和木鼻站年径流量序列周期大致为13年。(4)流域的年径流量总体呈现出下降的趋势,突变多发生在70年代,径流周期为14 a左右。

耦合深度学习的水丰水库入库径流中长期预测方法研究

少资料地区径流中长期预测关系发电厂中长期发电量的多寡,也对电厂短期经济运行有较强的指导作用。鸭绿江流域是东北地区重要的清洁能源基地,由于朝鲜控制了鸭绿江流域超过一半的面积,但其径流数据难以与中方共享,给鸭绿江流域径流中长期预测带来一定的阻碍。以鸭绿江流域水丰水库入库径流为研究对象,分别采用相空间重构模型(局域法、全局法)、LSTM模型、小波分析-LSTM模型、耦合相空间重构(局域法、全局法)和小波分析模型共6个模型方法对水丰水库旬、月及年尺度入库径流进行中长期径流预报工作,以平均绝对误差、平均绝对百分比误差与合格率对上述6个模型的预测结果进行精度评比。结果表明,年径流预报采用耦合相空间重构(全局法)和小波分析模型;月尺度径流预报中,1月预见期1-5月采用耦合相空间重构(局域法)和小波分析模型以及小波分析-LSTM模型效果较好,而6-12月耦合相空间重构(全局法)和小波分析模型具有明显优势;1年预见期中,小波分析-LSTM模型效果较好。旬尺度径流预测,1旬预见期采用小波分析-LSTM模型效果较好,3旬预见期采用小波分析-LSTM模型或耦合相空间重构(全局法)和小波分析模型,1年预见期中耦合相空间重构(全局法)和小波分析模型有明显优势。研究将为水丰水库及下游发电厂制定中长期调度计划提供支持。

基于Maan-Kendall检验和小波功率谱分析的滏阳河径流量变化研究

选用滏阳河流域典型水文站1961年~2020年的逐月径流量资料,运用Mann-Kendall非参数检验、Morlet小波分析法,探究滏阳河年径流量变化特征。结果表明,河北省近60年来径流量总体呈波状减少趋势,并以-0.112亿m^(3)/a的速率递减,但并不显著(P>0.05)。其多年平均径流量为14.96亿m^(3),丰枯变化与季节性降水、年际降水量丰度密切相关。径流量演变存在多个阶段性特征,但并未通过突变特征检验。其变化周期以3 a~5 a的短周期为主,此周期为7 a~8a和14 a。