The Mann-Kendall Test Modified by Effective Sample Size to Detect Trend in Serially Correlated Hydrological Series

The non-parametric Mann-Kendall (MK) statistical test has been popularly used to assess the significance of trend in hydrological time series. The test requires sample data to be serially independent. When sample data are serially correlated, the presence of serial correlation in time series will affect the ability of the test to correctly assess the significance of trend. To eliminate the effect of serial correlation on the MK test, effective sample size (ESS) has been proposed to modify the MK statistic. This study investigates the ability of ESS to eliminate the influence of serial correlation on the MK test by Monte Carlo simulation. Simulation demonstrates that when no trend exists within time series, ESS can effectively limit the effect of serial correlation on the MK test. When trend exists within time series, the existence of trend will contaminate the estimate of the magnitude of sample serial correlation, and ESS computed from the contaminated serial correlation cannot properly eliminate the effect of serial correlation on the MK test. However, if ESS is computed from the sample serial correlation that is estimated from the detrended series, ESS can still effectively reduce the influence of serial correlation on the MK test.     

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.     

乌鲁木齐市经济社会用水结构变化及未来趋势分析

分析城市用水结构的变化并科学预测未来需水结构,是编制水资源利用规划的前提和基础,对区域水资源的合理配置具有重要意义。在分析乌鲁木齐市社会经济各业用结构变化及其规律的基础上,探讨了其变化的主要原因,并预测了未来用水结构的发展趋势及其对未来水资源供需形势的影响,对协调未来可能利用水资源与社会经济发展的关系、制定合理的水资源配置方案、促进经济社会可持续发展提供参考。     

灰关联分析方法在NAM模型参数敏感性分析中的应用

应用NAM模型对资水水系夫夷水流域新宁水文站的洪水过程进行模拟。利用灰色系统关联分析方法来研究NAM模型参数对模型模拟径流深、洪峰流量和峰现时间的影响。计算实例表明：浅层蓄水容量对NAM模型模拟径流深的影响较大,地表径流和壤中流汇流时间常数对NAM模型模拟径流深的影响较小;地表径流系数、地表径流和壤中流汇流时间常数对NAM模型模拟洪峰流量的影响较大,壤中流出流时间对NAM模型模拟洪峰流量的影响较小;地表径流和壤中流汇流时间常数对NAM模型模拟峰现时间的影响较大。     

三门峡水库进出库水沙过程变化趋势及变异点分析

采用时间序列分析方法对三门峡水库天然情况下及建库后进出库水沙过程进行了变化趋势以及变异点分析,结果表明天然情况下水沙序列基本处于无趋势状态;而三门峡水库运行后进出库水沙序列大多出现了较明显的下降趋势,并且趋势在未来仍将延续;三门峡水库的运行对流量序列的影响相对较小,对年内径流调节有一定影响,对入库含沙量的调整较大。     

降水及人类活动对阜平流域径流的影响

为了研究近年来气候变化和人类活动影响条件下的阜平流域径流的演变规律,采用5 a滑动平均法和线性回归法,对阜平流域径流量、变化趋势及影响因素进行了分析,并利用降水径流经验统计模型估算了降水变化和人类活动对流域年径流量的影响程度。结果表明:降水量与径流量有一致性的变化趋势,降水量下降的趋势不明显,而径流量呈显著减少的趋势;1969—1979年、1980—1989年、1990—1999年、2000—2005年,受人类活动影响所减少的年均径流量分别占径流总减少量的21.04%、46.05%、58.30%、54.93%,受降水变化影响所减少的年均径流量分别占径流总减少量的78.96%、53.95%、41.70%、45.07%;随着年代的推移,人类活动对径流的影响逐渐增大,而降水变化的影响逐渐减小,20世纪80年代以后,人类活动导致径流量减少的贡献率要大于降水因素。     

黄河下游河道断面形态参数变化与主河槽萎缩趋势分析

本文采用时间序列分析的方法对黄河下游河道断面形态参数变化趋势及其变异点进行了分析，分析结果表明从20世纪50年代以来，断面形态参数发生了趋势性变化，特别是90年代以来各站平滩流量和平滩面积均有显著的下降趋势，花园口站、高村站和利津站平滩河宽出现了显著下降趋势，花园口站、艾山站平均水深显著下降，高村站和艾山站的平滩水位显著抬高，艾山站的宽深比也有显著增大的趋势。黄河下游河道主河槽萎缩的最显著特征就是断面平滩流量和平滩面积的显著下降，相应的平滩河宽、平均水深、最大水深出现不同程度的下降，另外可能还伴随着平滩水位和断面宽深比的上升。黄河下游河道主河槽在70年代开始初步萎缩，90年代以后进入严重萎缩期。     

A Quantitative Framework to Derive Robust Characterization of Hydrological Gradients

If ecological management of river ecosystems is to keep pace with increasing pressure to abstract, divert and dam, we must develop general flow–ecology relationships to predict the impacts of these hydrologic alterations. Regional flow gradient analyses are a promising tool to quickly reveal these functional relationships, but there are considerable uncertainties in this method because of variability in the historical extent of flow data across different rivers, combined with multiple indices characterizing the ecological attributes of flow regimes. In response, we outline an objective framework for analysing spatial hydrologic gradients that addresses three major sources of uncertainty: robust estimation of flow indices, the potential for temporal trends to confound spatial variation in flow regimes and the statistical robustness to detect underlying hydrological gradients. The utility of our framework was examined in relation to flow regimes across multiple braided river catchments in Canterbury, New Zealand. We found that a subset of flow indices could be robustly estimated using only 10 years of flow data, although indices that captured flow ‘timing’ required longer time series. Temporal trends were unlikely to confound conclusions from a spatial hydrologic gradient analysis, and there were three statistically supported hydrologic gradients related to flow magnitude, flow variability and low flow events. The widespread application of robust spatial flow gradient analyses has the potential to further our understanding of how altered flow regimes affect the ecology of freshwater and riparian ecosystems, thereby providing the evidence base to inform river management. Copyright © 2016 John Wiley & Sons, Ltd.     

支持向量机的混沌序列预测模型及在径流中应用

混沌和支持向量机理论为研究复杂多变的非线性水文时间序列开辟了新的途径。给出了应用支持向量机回归原理的混沌时间序列非线性的预测建模的思路、特点及关键参数的选取。根据重构相空间理论对月径流过程进行相空间的重构,探讨了支持向量机混沌时间序列非线性预测模型在月径流预测中的应用,在支持向量机建模过程中引入了经向基核函数,简化了非线性问题的求解过程。实例表明,该模型能较好地处理复杂的水文数据序列,且有较好的预测精度。     

南流江流域降水序列周期特征及变化趋势

降水序列的变化规律和变化趋势是流域防洪抗旱时需要考虑的重要问题。以北部湾经济区南流江流域为例,尝试利用小波分析和R/S分析方法研究年降水量周期特征和变化趋势。研究结果表明:在短周期范围内,南流江上游流域具有3~8a的主周期,未来年降水量出现减少的趋势;中游流域具有3~8a的主周期,未来年降水量出现增加的趋势;下游流域具有5~8a的主周期,未来年降水量出现增加的趋势。因此,未来短期内南流江干流的防洪重心主要在于中下游流域,需要预防突发性降雨。     

Trend Analysis of Streamflow Drought Events in Nebraska

A streamflow drought event, defined by applying the threshold level approach on streamflow time series, is composed of three parameters: duration, severity and magnitude. This study reveals statistical characteristics on streamflow drought event parameters and detects spatial and temporal trends in the streamflow drought in terms of frequency, duration and severity in Nebraska. The studies are conducted on three time periods: 1970–2001 (60 stations), 1950–2001 (43 stations), and 1932–2001 (9 stations). The statistical tests performed on the drought event parameters include correlation between event parameters tests, Hurst coefficients and lag-one coefficients, and trend-free pre-whitening Mann–Kendall (TFPW-MK) tests. The analysis shows that there is no uniform trend on the streamflow drought in the whole state. However, some trends are evident for specific regions. Specifically, it is most likely that droughts in the Republican watershed have become more intense; whereas the drought has become slightly alleviated in the Missouri and nearby watersheds.     

黄河下游河道断面形态参数变化与主河槽萎缩趋势分析

采用时间序列分析法对黄河下游河道断面形态参数变化趋势及其变异点进行了分析。结果表明从20世纪50年代以来,特别是90年代以来黄河下游花园口站、高村站、艾山站和利津站断面形态参数发生了趋势性变化,主河槽变化的最显著特征就是断面平滩流量下降,相应的平滩面积、平滩河宽、平均水深、最大水深均出现不同程度的减小,平滩宽深比增大。变异点分析表明黄河下游河道主河槽总体上在1970—1975年开始萎缩,1990年以后进入严重萎缩期。     

黄河中游气温变化趋势及其对蒸发能力的影响

气温是影响流域蒸发的一个重要因素。收集整理了黄河中游6个站点的气象资料,采用斯波曼秩次相关检验法、坎德尔秩次相关检验法等多种方法相结合的途径,对黄河中游代表性站点的气温变化趋势进行了显著性分析检验。根据蒸发能力与气温的关系,建立了简捷且实用的指数型蒸发能力估算公式,进一步分析了气温变化对流域蒸发能力的影响。结果表明:近几十年来,黄河流域气温具有明显的升高趋势。气温与蒸发能力之间具有良好的正相关关系,在气温升高1℃的情况下,流域蒸发能力约增加5.0%~7.0%。     

降水变化和人类活动对浏阳河流域径流的影响

定量评估降水变化和人类活动对浏阳河流域径流的影响,有助于更合理地利用流域水资源。采用线性拟合、滑动平均和累积距平等方法分析了1969—2013年浏阳河流域径流和降水的演变规律及其相关关系,应用累积斜率变化率比较法定量估算了不同时期降水变化和人类活动对径流量变化的贡献率。结果表明:浏阳河流域降水量表现为增加趋势,上升率为3 mm/(10 a);年径流量表现为下降趋势,下降率为2.7 (m³·s^-1)/(10 a);降水和径流在1988年和1999年均发生显著性突变,经历了“减少—增多—减少”的交替变换。与基准期1969—1988年相比,1989—1998年和1999—2013年这2个时期的降水量变化对径流量变化贡献率依次为56.8%,7.62%,而人类活动对径流量的贡献率依次为43.2%,92.38%,可见人类活动已成为影响浏阳河流域径流变化的主要因素。     

拱坝结构诱导缝力学参数反演分析及工程应用

确定设置在拱坝结构中的诱导缝力学参数是工程界的一个难题，一直未能很好解决。本文提出了一种新方法，采用BP神经网络方法与有限单元法相结合的联合反演方法，对诱导缝接触面的力学参数进行反演，较好地解决了该问题。并针对超大型实际工程小湾拱坝进行应用，结果表明通过对诱导缝面的法刚和切刚力学参数反演，有限元计算值与实际监测值吻合较好；当前施工浇筑状态下整个诱导缝面处于受压闭合状态,诱导缝靠近上游侧的压应力和挤压变形大于靠廊道侧的压应力和挤压变形，并且中间坝段大于两端坝段。本方法很好地解决了实际工程问题，具有相当的参考意义。     

时间序列模型分析威海市近 50 年气温变化特征

利用时间序列模型,以及趋势分析、小波变换、M-K突变检验等统计学分析方法,分析了威海站1964年-2013年的平均气温、平均最高气温和平均最低气温的年变化、年平均气温的季节变化、时频特点,并对平均气温变化进行了突变检验,发现1964年-2013年威海市年平均气温呈上升趋势,气温倾向率为0.35℃/(10a);各季节气温倾向率分别为0.427℃/(10a)、0.268℃/(10a)、0.241℃/(10a)和0.287℃/(10a),其中春季(0.427℃/(10a))增温对该市年平均气温变化的贡献最大;春季气温呈现降-升-降-升-降的交替变化,为四季气温变化最明显的季节;年平均气温突变发生在1987年;各个季节在发生突变后均升温趋势显著。     

三峡库区龙河流域降雨和人类活动对水沙关系变化贡献率分析

以三峡库区中心区域的龙河流域为研究对象,利用1963—2010年流域水沙资料,采用Pettitt突变点检验、累积距平法及双累积曲线法分析了该流域输沙量和降雨量的变化趋势,判别出降雨量在1982年、输沙量在1982年和1990年发生了突变。并采用累积量斜率变化率比较法分析了1963—1981年,1982—1990年,1991—2010年3个时段降雨量和人类活动在龙河流域输沙量变化中的相对贡献率。研究表明:以1963—1981年为基准期,1982—1990年间降雨量和人类活动贡献率分别为29.49%和60.51%,1991—2010年间分别为3.38%和96.62%;以1982—1990年为基准期时,1991—2010年人类活动对输沙减小的贡献率为100%。该研究揭示了1963—2010年输沙量的变化趋势及降雨和人类活动对其贡献率,研究不仅对该区水土流失治理、水土保持效益评价具有重要意义,同时为研究三峡水库区间水沙锐减的原因提供一定的理论支持。     

皇甫川流域产流产沙数学模型及水沙变化原因分析

该模型是从泥沙运动力学的基本理论出发，结合水文学，气象，土壤学和地理地貌学的原理建立起来的。并着重解决了在大流域计算中的流域的地理，地貌的差异性和降雨在时空分布上的不均匀性问题。     

海河流域历史水旱序列变化规律研究

对历史时期旱涝灾害的重建及其影响研究是当前探求气候事件发生规律的热点之一,而对周期的计算和对突变点的检测又是探求规律的重要手段。基于海河流域540a旱涝等级资料,运用谱功率分析、小波分析、指数分析和Mann-Kendall法等方法分别对海河流域水旱发生周期和突变点进行计算分析。结论显示：海河流域水旱灾害在历史上分别存在10a,23a,37a和75a左右的主导周期;在17至18世纪间,流域经历了旱型－涝型的转变。     

Trend analysis of water quality in some rivers with different degrees of development within the São Paulo State,Brazil

Time series of dissolved oxygen (DO), biochemical oxygen demand (BOD), nitrate, total phosphorus, chloride, ammonia and faecal coliforms (FC), monitored by CETESB (‘Companhia de Tecnologia de Saneamento Ambiental’), in the period from 1979 to 2001, were analysed in seven river basins located in the São Paulo State, one of the most developed regions in Brazil. The selected rivers, Piracicaba, Mogi‐Guaçu, Turvo Grande, Peixe, Aguapeí, São José dos Dourados and Alto Paranapanema have different degrees of development concerning industrial, agricultural and population growth. Trend analysis methodology was based on graphical exploratory analysis followed by confirmation through statistical tests. Results showed impoverishment of the water quality conditions in most of the studied basins, represented by the positive trends of the parameters (BOD, nitrogens, total phosphorus, clorate and FC) and negative trend of the parameter (DO). Among the analysed basins, the Piracicaba River is the most severely affected with higher variations in the magnitude followed by the basins of the Mogi‐Guaçu, Turvo Grande, Peixe and Aguapeí Rivers. On the other hand, the Alto Paranapanema and São José dos Dourados basins are the least affected. Copyright © 2008 John Wiley & Sons, Ltd.