The changes in the annual distribution of mountain runoff during the period of 1965-2018 in Hexi Corridor,Northwest China

The annual distribution characteristics of river runoff in arid regions have significant implications for water resource stability and management.Based on the mountain runoff data from 1965 to 2018,this study examines the annual change characteristics of monthly runoff of the Shiyang River Basin,Heihe River Basin,and Shule River Basin in the Hexi Corridor,Northwest China.Many indexes are used and analyzed,including the coefficient of variance,the complete regulation coefficient,the concentration degree and concentration period,the magnitude of change,the skewness coefficient,and the kurtosis coefficient of the annual distribution curves.The results reveal the following:(1)The inhomogeneity of annual runoff distribution in the Taolai River and the rivers to the west of it,except the Shiyou River,show an increasing trend.Conversely,the inhomogeneity of the rivers to the east of the Taolai River generally show a downward trend,but the coefficient of variance value is still very high.(2)In the Shiyang River Basin,the annual distribution of the concentration period is characterized by a relatively discrete pattern.Conversely,the Heihe River Basin exhibits a relatively concentrated pattern,and the distribution pattern of the Shule River Basin is quite different.Notably,all concentration periods in the three basins have shifted backward after the 2000s.(3)The Shiyang River Basin exhibits disordered annual distribution curves of runoff in different years.In contrast,the Heihe River Basin presents a typical‘single-peak’pattern with a prominent right-skewed.The Shule River Basin has regular distribution curves,with a gradually significant‘double-peak’pattern from east to west.Overall,there has been a slight change in runoff in the Shiyang River Basin,while the Heihe River Basin and Shule River Basin have experienced significant increases in runoff.The annual distribution curves of runoff in the Liyuan River and the rivers to the east of it exhibit a gentle peak pattern,and the appearance probability of extreme runoff during the year is low.Conversely,the rivers to the west of the Liyuan River,excluding the Danghe River,display a sharp peak and thick tail pattern,indicating that the appearance probability of extreme runoff during the year is high.These findings have practical implications for the planning and management of water resources in the Hexi Corridor.Moreover,they provide a solid foundation for predicting future changes in regional water resources.

Trend Analysis in Annual and Monthly Pan Evaporation and Pan Coefficient in the Context of Climate Change in Togo

Trend analysis was performed for the long-term measured pan evaporation and estimated pan coefficient for 4 meteorological stations during 1976-2011 in Togo. Measured pan evaporation was recorded at four meteorological stations in Togo for the global period of 1976 to 2011 at Lome, Tabligbo, Atakpame, and Sokode. ETo was estimated using the Penman-Monteith model. The Mann-Kendall test was used for trend analysis. The results showed that annual Epan varied from 1803 to 2081 mm at Lome, from 1294 to 1496 mm at Tabligbo, from 1605 to 1974 mm at Atakpame and from 1839 to 1990 mm at Sokode. It had significant increasing trend at Lome, Tabligbo, and Sokode and a negative trend at Atakpame. Monthly Epan varied from 137 to 197 mm at Lome, 89 to 149 mm at Tabligbo, 137 to 214 mm at Atakpame and from 137 to 190 mm at Sokode. At Lome, Kpan varied from 0.61 to 1.17 and averaged 0.81. At Tabligbo, Kpan varied from 0.59 to 0.98 and averaged 0.75. At Atakpame, Kpan varied from 0.5 to 2.0 and averaged 1.12. At Sokode, Kpan varied from 0.43 to 1.92 and averaged 0.98. Monthly mean Kpan is recommended for use in hydrological studies, irrigation scheduling and water management in Togo.

Analysis of Chaotic Characters for the Monthly Runoff Se-ries at Fudedian Station in Liaohe Bain

The evolution of monthly runoff is affected both by climate environment and human activities, and its characteristics play an important role in runoff prediction and simulation. In this paper, the G-P and the principal component analysis method, which are both based on the reconstruction theory of the phase space, are used to study the chaos characteristics of the monthly runoff series at Fudedian station in Liaohe basin. The results show that the monthly runoff series have a large probability of chaos.

Some Annual Variation Characteristics for the Northern Hemispheric Monthly Mean Precipitation Fields

By the utilization of monthly precipitation data from all stations in the Northern Hemisphere annexed to the 'World Survey of climatology, Vol. 1-15', the distributions of the maximum precipitation months (MPM), the annual relative precipitation (ARP) and the monthly relative precipitation (percent of annual) in January and July are respectively mapped. Moreover the distributions of intermonthly relative precipitation variabilities from January to December are plotted as well. From these figures, the precipitation in the Northern Hemisphere may be classified into three types(continental, oceanic and transitional types) and 17 regions. The precipitation regime may also be divided into two patterns, the global and regional patterns. The global pattern consists of planetary front system and ITCZ and its inter-monthly variation shows the north-and-south shift of the rain belt; the regional pattern consists of the sea-land monsoon and plateau monsoon regime, in which the inter-monthly variation of rain belt shows a east-and-wcst shift.

Analysis on the Variations of Annual Runoff Distribution in the Weihe Basin

With the impact of climate change and the increasing intensity of human activities,the hydrological regime had changed,including annual runoff distribution,which was related with water resources management and ecological construction. Based on the monthly runoff data for more than 40 years of the Beidao,Xianyang,Huaxian station on Weihe Basin,the annual distribution characteristics of runoff were studied. Several indices related to attributes of uneven,concentrate degree and variation amplitude were calculated,and the results showed that there had obvious fresh and drought seasonal changes in 1990s. The annual runoff distribution had changed a lot,mainly because of runoff decrease in the wet season. The Huaxian station,which locates at the upper reaches,had a higher unevenness,concentration and relative variation rate than that of the Beidao and Xianyang station.

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.

Documented changes in annual runoff and attribution since the 1950s within selected rivers in China

To enable local water resource management and maintenance of ecosystem integrity and to protect and mitigate against flood and drought, it is necessary to determine changes in long-term series of streamflow and to distinguish the roles that climate change and human disturbance play in these changes. A review of previous research on the detection and attribution of observed changes in annual runoff in China shows a decrease in annual runoff since the 1950s in northern China in areas such as the Songhuajiang River water resources zone, the Liaohe River water resources zone, the Haihe River water resources zone, the Yellow River water resources zone, and the Huaihe River water resources Zone. Furthermore, abrupt changes in annual runoff occurred mostly in the 1970s and 1980s in all the above zones, except for some of the sub-basins in the middle Yellow River where abrupt change occurred in the 1990s. Changes in annual runoff are found to be mainly caused by climate change in the western Songhuajiang River basin, the upper mainstream of the Yangtze River, and the western Pearl River basin, which shows that studies on the impact of climate change on future water resources under different climate change scenarios are required to enable planning and management by agencies in these river basins. However, changes in annual runoff were found to be mainly caused by human activities in most of the catchments in northern China (such as the southern Songhuajiang River, Liaohe River, Haihe River, the lower reach and some of the catchments within the middle Yellow River basin) and in middle-eastern China, such as the Huaihe River and lower mainstream of the Yangtze River. This suggests that current hydro-climatic data can continue to be used in water-use planning and that policymakers need to focus on water resource management and protection.

The complex nonlinear systems with fractal as well as chaotic dynamics of annual runoff processes in the three headwaters of the Tarim River

This paper attempted to identify fractal and chaotic characteristics of the annual runoff processes in headwaters of the Tarim River.Methods of fractal analyses were used to explore several aspects of the temporal changes from 1957 to 2002.The main findings are as follows:(1) The annual runoff processes of the three headwaters of the Tarim River are com-plex nonlinear systems with fractal as well as chaotic dynamics.(2) The correlation dimensions of attractor derived from the time series of the annual runoff for the Hotan,Yarkand and Aksu rivers are all greater than 3.0 and non-integral,implying that all three rivers are chaotic dynamical systems that are sensitive to initial conditions,and the dynamic modeling of their annual runoff process requires at least four independent variables.(3) The time series of annual runoff in each river presents a long-term correlation characteristic.The Hurst exponent for the period of 1989 to 2002 suggests that we may expect to see an increasing trend in the annual runoff of the Aksu and Yarkand rivers in the years after 2002,but a decreasing tendency for the Hotan River in the same period.

Quantitative research of annual runoff distribution characteristics in the Dagujia River basin,Yantai,China

Mann-Kendall method and minimum variance method are used in this study to analyze the mean value variable-point of the runoff data observed by Fushan Hydrological Station in the Dagujia River basin from 1966 to 2004. Based on the results, the runoff time is divided into four periods with the similar hydrological variation character. The annual runoff distribution characters in the Dagujia River basin are discussed by using the non-uniform coefficients, concentration degree and concentration period, variation range, etc. The results indicate that: (1) River runoff is very unevenly distributed throughout the year in Dagujia River. About 90% of runoff is in the period from June to October, while the runoff from November to April of the next year is lower. (2) The annual runoff distribution characters during 1966-1971 are very similar to that of 1982-1996, and the runoff of 1972-1981 is almost similar to that of 1997-2004. (3) The annual runoff distribution characters have changed obviously during 1997-2004 compared with the other periods, which makes it more difficult to exploit and use the water resource in the future.

Annual Runoff and Sediment in Duhok Reservoir Watershed Using SWAT and WEPP Models

Estimation of runoff volume and sediment load is the main problem that affects the performance of dams due to the reduction in the storage capacity of their reservoirs and their effect on dam efficiency and operation schedule. The simulation models can be considered for this purpose if the continuous field measurements are not available. Soil and Water Assessment Tool (SWAT) and Water Erosion Prediction Project (WEPP) models were applied to estimate the annual runoff volume and sediment load for Duhok Dam Reservoir in north of Duhok/Iraq for the period 1988-2011. The estimated annual runoff volume varied from 2.3 to 34.7 MCM for considered period. Those values were affected by rainfall depth, intensity and runoff coefficient. The resultant annual runoff coefficient for the studied area ranged from 0.05 to 0.35 (average was 0.18) causing an average runoff volume of about 14 MCM. The results of sediment routing indicated that the values of sediment yields varied from 50 to 1400 t/km2/year depending on sub basin properties. The average annual sediment load from the whole watershed is about 120 × 103 ton. The estimated total sediment arrived to Duhok Reservoir for the considered period 1988-2011 was about 2.9 × 106 ton. The results indicate that both models gave reasonable results in comparison with measured values. Based on statistical criteria, the results of both models are close to gather.

黄土高原径流侵蚀功率输沙模型的改进

水土流失对流域生态危害严重,输沙量模拟和预测可以为流域水土流失防治提供依据,因此精确的输沙模型是流域水土流失治理的重要工具。为了精确模拟变化环境下黄土高原年输沙量,该研究基于黄土高原19个水文站的径流和输沙数据,通过随机森林变量重要性度量方法评估年径流侵蚀功率、淤地坝指数、淤地坝相对指数、归一化植被指数、不透水地面积等因子对流域年输沙量的影响,使用非线性最小二乘法估算年输沙模型参数,对比分析不同因子组合的年输沙模型精度,提出适用性较强的黄土高原年输沙模型,据此开展年输沙量变化贡献率分析。结果表明:1)以幂函数形式构建的仅含径流侵蚀功率单因子输沙模型精度与流域面积有显著的负相关关系,相关系数为-0.505(P<0.05),模型精度随着流域面积增大而下降,在面积大于7000 km^(2)的流域适用性较差;2)年径流侵蚀功率、淤地坝指数及不透水地面积因子组合建立的多因子年输沙模型在黄土高原适用性最佳,模型在率定期纳什效率系数平均值为0.84,均方根误差平均值为0.21亿t,在验证期纳什系数平均值为0.79,均方根误差平均值为0.27亿t。3)影响研究流域年输沙量变化的因素依次是:年径流侵蚀功率、不透水地面积和淤地坝指数。研究可以为黄土高原不同区域水土流失防治和生态治理工作提供理论支撑。

基于地球河流扇预测模型的火星地表水径流量预测

【目的】火星表面的水活动地质历史一直是科学界关心的热点,直接影响着火星探测的研究方向。【方法】根据火星和地球的可对比性,建立了融合345个地球现代河流扇沉积的数据集并形成了高精度扇体面积预测模型,从而识别火星上的河流扇沉积,预测火星河流扇发育期的地表水径流量。【结果】结果表示,在火星南部高地霍尔顿陨石坑附近识别出一个面积约84.35 km^(2)的典型河流扇沉积,并反向预测出该扇体形成需要的年平均地表水径流量为1.8828×10^(6)m^(3),推测出该区域径流量不是由单一降水构成,为雪山(冰川)融水和降水多种来源。【结论】该成果是河流扇研究在行星沉积学中的应用,为进一步深入研究火星和其他天体地表水活动提供了新的方法。

广东省主要江河68年径流量年际变化特征分析

基于广东省西江、北江、东江、韩江、鉴江等5条主要江河1956—2023年共68 a的径流量资料,分析了径流量的基本特征和趋势性、自相关性、随机性和空间相关性等变化特性。结果表明,5条江河径流量的年际变化总体较大;西江的平水年较多,而其他江河的特丰年和特枯年较多;5条江河径流量的年际变化趋势性不明显,北江、鉴江、西江呈不显著上升趋势,东江、韩江呈不显著下降趋势;径流量序列的年际自相关性很低,接近于纯随机性,旱涝切换的规律性不强;西江与其他4条江河的年径流量序列的互相关性较弱,互补性较强;北江、东江和韩江的年径流量序列的互相关性较强,同丰同枯现象明显;鉴江的年径流量序列与其他江河的互相关性也较弱。

Estimating runoff coefficient for quantity assessment of roof rainwater harvesting system

In order to accurately estimate the runoff coefficient for the quantity assessment of the roof rainwater harvesting system RRHS great differences in the value of event runoff coefficient ψERC were observed by field monitoring under different roof types roof slope and material and diverse rainfall distributions rainfall depth and intensity in three years 2010 to 2012 in Handan Hebei China.The results indicate that the distribution of ψERC is more highly correlated with the event rainfall depth than other factors. The relationship between ψERC and the rainfall depth can be well represented by the piecewise linear function.Further based on the daily rainfall data over the period from 1960 to 2008 the value of the annual runoff coefficient ψARC is calculated. Although the total rainfall depth in each year is different ψARC in Handan can be considered as a constant 0.62 approximately. The results can be used for the quantity assessment and performance analysis of the RRHS.

海绵型建筑与小区年径流污染控制率计算方法探讨

【目的】年径流污染控制率是海绵城市建设中的核心控制指标,对指导海绵设施设计具有重要意义。但其设计计算过程中的计算方法与公式存在不统一或不合理的问题,须探究更适用于实际工程的计算公式。【方法】梳理了国内外对于海绵设施污染物去除率的取值来源与计算方法,分析了目前工程设计中单一海绵设施对污染物去除率的取值和地块污染平均去除率计算方法存在的问题,并对比不同地区雨水管理径流控制指标,从定义出发推导更适用于建筑与小区小尺度流域的计算方法。【结果】在建筑与小区等小尺度流域的设计中,与其他三种地块海绵设施对悬浮物的平均去除率的算法相比,采用海绵设施的有效汇水面积进行加权平均计算会更加合理;而在年径流污染控制率的计算中,引入累积污染物负荷率与累积径流体积率比例,将其转化为年平均径流污染量控制率与污染物平均去除率的乘积进行计算会更加合理。【结论】对于年径流污染控制率的计算应该积极开展试验或数值模拟,并形成适合国内实际情形的数据库。应该提高设计人员对源头海绵设施污染物去除过程的认知,避免在建筑与小区等小尺度流域的设计计算中采用不合适的公式而引起的误差。

水库运用对金沙江下游水沙变化的影响

大型水库运用后,金沙江下游水沙时空分布发生重大变化。本文基于金沙江下游干支流水沙观测资料,分析了下游流域水沙时空分布特性。1954-2021年,金沙江下游径流主要来源为金沙江中游及雅砻江,两者年均径流量为1150.73亿m^(3),占总来水量的80.75%;年输沙量主要来自下游区间,其年均来沙量为9943.17万t,占总输沙量的48.12%。运用Mann-Kendall突变检验、R/S分析以及双累积曲线法,分析水库运用对金沙江下游水沙变化趋势的影响。结果表明:1954-2021年金沙江下游水库运用对年径流量变化趋势无明显影响,而对流域年输沙量影响显著。金沙江下游出口水沙关系在1998、2010及2012年发生突变,主要原因为雅砻江、金沙江中游、下游干流上大型水库的拦沙运用,导致下游出口含沙量由1.82 kg/m^(3)逐步降低为1.31、0.86、0.01 kg/m^(3)。利用金沙江下游干支流水沙关系及沙量平衡原理,分别计算局部区间水库拦沙对流域总减沙量的贡献度。1998-2009年二滩水电站建成运行,金沙江下游出口总减沙率为35.16%,雅砻江水库拦沙对下游总减沙贡献度为32.88%;2010-2012年金安桥等中游水电站运行后,下游出口总减沙率为51.43%,金沙江中游、雅砻江、三堆子至白鹤滩区间和白鹤滩至向家坝区间对下游总减沙贡献度分别为21.54%、23.10%、30.67%、24.69%;2013-2021年金沙江下游梯级水库运行后,下游出口总减沙率为99.37%,4个区间对来沙量减少的贡献度分别为19.64%、14.72%、12.34%、53.30%。

黑河上游年径流模拟模型优选与归因分析

【目的】本研究旨在深入探究人类活动与气候变化对黑河上游年径流量的影响,为区域水资源保护与规划利用提供科学支持。【方法】研究综合Mann-Kendall非参数统计检验、Pettitt检验和滑动t检验方法,对1954—2020年黑河上游年径流序列进行趋势检验,识别年径流序列趋势变化的突变点并划分基准期与分析期。在此基础上,采用BP神经网络模型、灰色时间序列模型和多元线性回归模型,模拟基准期年径流变化,优选模拟效果最佳模型,进而借助优选模型与径流变化归因方法,定量解析人类活动与气候变化要素对年径流变化的驱动规律。【结果】趋势检验发现,年径流序列在1982年和2006年前后发生了突变,黑河上游年径流序列可划分为1954—1982年(基准期)、1982—2006年(分析期1)和2006—2020年(分析期2)3个阶段。在基准期年径流序列的模拟中,BP神经网络模型在验证期的相对误差(0.79%)、纳什效率系数(0.84)与拟合优度(0.84)3个参数上相较其他模型优势明显。借助神经网络模型进行年径流变化归因分析,发现人类活动导致年径流在1982—2020年间减少的平均值为7.56×10^(8) m^(3)。但2006—2020年间黑河上游人类活动对径流的负面贡献率较1982—2006年间减少约18.00%。详细解析气候变化对年径流量的影响,发现在2006—2020年间,降水量与蒸散发对年径流的贡献率较1954—1982年分别增加约11.00%和8.00%。【结论】BP神经网络模型对于黑河上游年径流序列模拟有较好效果,模拟合格率达94.23%,最大误差仅为1.36%;黑河流域上游年径流量序列在1982年和2006年发生了趋势突变,1982年后人类活动强度增大导致上游年径流量减小,2006年后黑河流域综合治理效果显现,人类活动对年径流量的负面效应减弱;1982—2020年期间的气候变化影响中,蒸散发与降水对径流的贡献分别占46.57%与53.43%。

成都市主城区道路冲洗径流污染研究

为评估城市道路冲洗径流污染程度,于2022年3—8月在成都市主城区内选取交通性路段、商业性路段、生活性路段和餐饮性路段进行冲洗水径流采样,通过对采样结果进行差异显著性分析,探究道路类型、降雨冲刷和较高气温(>30℃)对冲洗径流污染负荷的影响,综合考虑这3个因素推导道路冲洗径流年污染排放量估算公式。结果表明:不同类型道路冲洗径流污染程度存在差异,其中,餐饮性路段严重,生活性路段和商业性路段次之,交通性路段最轻;通过相关性分析推测,路两侧餐饮经营活动的污染排放是导致不同类型道路冲洗径流污染负荷值存在差异的主要原因;此外,较高气温(>30℃)会导致道路冲洗经流污染负荷升高,而降雨则反之;以成都市为例进行估算,2022年主城区道路冲洗径流中化学需氧量(chemical oxygen demand,COD)、总氮(total nitrogen,TN)、总磷(total phosphorus,TP)、悬浮物(suspended solids,SS)和氨氮(ammonia nitrogen,NH3-N)的排放量分别为3 506、167.56、30.32、1 441、55.687 kg。

Discovery of the Significant Impacts of Swell Propagation on Global Wave Climate Change

This study compared the differences in the wave climate in the South China Sea and North Indian Ocean under these two datasets:ERA-40 wave reanalysis and Mei’s hindcast wave data.In the numerical calculation of regional ocean waves,the wave climate characteristics exhibited significant bias if the influence of external swells(swells from afar)was not fully considered,which may provide an incorrect basis for global climate change analysis.1)The trends of the significant wave height(SWH)obtained from the two datasets showed significant differences,such as those of the Bay of Bengal and the Java Sea in June-July-August.For the past 45 years,SWH from ERA-40(SWH-ERA)exhibited a significant annual increase in low-latitude waters of the North Indian Ocean(0.2-0.6 cm yr^(-1))and South China Sea(0.2-0.8 cm yr^(-1)).2)In the Bay of Bengal,the SWH-ERA in each month was generally 0.5 m higher than the SWH from Mei’s hindcast wave data(SWH-Mei)and can reach 1.0 m higher in some months.3)In the Bay of Bengal,SWH-ERA and SWH-Mei increased significantly at annual rates of 0.13 and 0.27 cm yr^(-1),respectively.This increasing trend was mainly reflected after 1978.SWH-ERA showed a trough in 1975(1.33 m)and a crest in 1992(1.83 m),which were not reflected in SWH-Mei.

1984年~2018年四卯酉河径流演变规律及归因分析

为揭示四卯酉河径流演规律及其影响因素,基于四卯酉闸水文站1984年~2018年的实测径流数据,采用Mann-Kendall检验法、Pettitt检验法、Morlet小波分析法分析四卯酉河年际变化规律,采用不均匀系数、集中度与集中期三个指标分析四卯酉河径流年内分配规律,采用双累积曲线定量分析四卯酉河径流演变原因。结果表明:四卯酉河径流量呈现显著上升趋势,并于2004年发生显著向上突变,径流主周期为28 a、18 a、13 a、9 a;四卯酉河径流年内分配较为均匀;降水因子和人类活动因子对四卯酉河径流变化贡献率分别为3.3%、96.7%,人类活动引起的不透水面的变化是导致四卯酉河径流变化的重要原因。