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.

Impacts of Climate Change on Spatial and Temporal Distribution of Runoff and Sediment Yield in Xixi Watershed of Jinjiang Basin

Based on meteorologic data in Xixi Watershed from 1972 to 1979, the SWAT model was applied to simulate the response of runoff and sediment yield in Xixi Watershed to climate change under 24 kinds of climate change scenarios, and then the spatial and temporal distribution of change rates of the runoff and sediment were analyzed. The results showed that the runoff yield would increase with the increase of precipitation or decrease of temperature, and the sediment yield would increase with the increase of precipitation or increase of temperature; the runoff would be more sensitive to variations in precipitation than to variations in temperature, and precipitation change would lead to more obvious change in the run- off yield; the temporal distribution of change rates of the runoff and sediment yield would be uneven in the 12 months, and the variation trends of the two change rates in the 12 months would be accordant; the spatial distribution of change rates of the runoff and sediment yield would be uneven in the sub-watersheds, and the change rate of the runoff yield would be bigger in the sub-watersheds where the runoff yield in the basic period would be smaller. This study can provide decision-making basis for sustainable development of Jinjiang Basin.

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.

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.

Estimation of runoff and sediment yield in the Redrock Creek watershed using AnnAGNPS and GIS

Sediment has been identified as a significant threat to water quality and channel clogging that in turn may lead to river flooding. With the increasing awareness of the impairment from sediment to water bodies in a watershed, identifying the locations of the major sediment sources and reducing the sediment through management practices will be important for an effective watershed management. The annualized agricultural non-point source pollution(AnnAGNPS) model and newly developed GIS interface for it were applied in a small agricultural watershed, Redrock Creek watershed, Kansas, in this pilot study for exploring the effectiveness of using this model as a management tool. The calibrated model appropriately simulated monthly runoff and sediment yield through the practices in this study and potentially suggested the ways of sediment reduction through evaluating the changes of land use and field operation in the model for the purpose of watershed management.

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.

Effects of soil conservation practices on soil erosion and the size selectivity of eroded sediment on cultivated slopes

Soil conservation practices can greatly affect the soil erosion process,but limited information is available about its influence on the particle size distribution(PSD)of eroded sediment,especially under natural rainfall.In this study,the runoff,sediment yields,and effective/ultimate PSD were measured under two conventional tillage practices,downhill ridge tillage(DT)and plat tillage(PT)and three soil conservation practices,contour ridge tillage(CT),mulching with downhill ridge tillage(MDT),and mulching with contour ridge tillage(MCT)during 21 natural rainfall events in the lower Jinsha River.The results showed that(1)soil conservation practices had a significant effect on soil erosion.The conventional tillage of DT caused highest runoff depth(0.58 to 29.13 mm)and sediment yield(0.01 to 3.19 t hm^(-2)).Compared with DT,the annual runoff depths and sediment yields of CT,MDT and MCT decreased by 12.24%-49.75%and 40.79%-88.30%,respectively.(2)Soil conservation practices can reduce the decomposition of aggregates in sediments.The ratios of effective and ultimate particle size(E/U)of siltand sand-sized particles of DT and PT plots were close to 1,indicating that they were transported as primary particles,however,values lower/greater than 1 subject to CT,MDT and MCT plots indicated they were transported as aggregates.The ratios of E/U of claysized particles were all less than 1 independently of tillage practices.(3)The sediments of soil conservation practices were more selective than those of conventional tillage practices.For CT,MDT and MCT plots,the average enrichment ratios(ERs)of clay,silt and sand were 1.99,1.93 and 0.42,respectively,with enrichment of clay and silt and depletion of sand in sediments.However,the compositions of the eroded sediments of DT and PT plots were similar to that of the original soil.These findings support the use of both effective and ultimate particle size distributions for studying the size selectivity of eroded sediment,and provide a scientific basis for revealing the erosion mechanism in the purple soil area of China.

Sensitivity of runoff to climatic variability in the northern and southern slopes of the Middle Tianshan Mountains,China

Temperature and precipitation play an important role in the distribution of intra-annual runoff by influencing the timing and contribution of different water sources.In the northern and southern slopes of the Middle Tianshan Mountains in China,the water sources of rivers are similar;however,the proportion and dominance of water sources contributing to runoff are different.Using the Manas River watershed in the northern slope and the Kaidu River watershed in the southern slope of the Middle Tianshan Mountains as case studies,we investigated the changes in annual runoff under climate change.A modified hydrological model was used to simulate runoff in the Kaidu River and Manas River watersheds.The results indicated that runoff was sensitive to precipitation variation in the southern slope and to temperature variation in the northern slope of the Middle Tianshan Mountains.Variations in temperature and precipitation substantially influence annual and seasonal runoff.An increase in temperature did not influence the volume of spring runoff;but it resulted in earlier spring peaks with higher levels of peak flow.Damages caused by spring peak flow from both slopes of the Middle Tianshan Mountains should be given more attention in future studies.

Sediment yield and erosion–deposition distribution characteristics in ephemeral gullies in black soil areas under geocell protection

Investigating the effect of geocells on the erosion and deposition distribution of ephemeral gullies in the black soil area of Northeast China can provide a scientific basis for the allocation of soil and water conservation measures in ephemeral gullies.In this study,an artificial simulated confluence test and stereoscopic photogrammetry were used to analyze the distribution characteristics of erosion and deposition in ephemeral gullies protected by geocells and the effect of different confluence flows on the erosion process of ephemeral gullies.Results showed that when the confluence flow was larger,the effect of geocell was more evident,and the protection against ephemeral gully erosion was stronger.When the confluence flow rates were 0.6,1.8,2.4,and 3.0 m^(3)/h,ephemeral gully erosion decreased by 37.84%,26.09%,21.40%,and 35.45%.When the confluence flow rates were 2.4 and 3.0 m^(3)/h,the average sediment yield rate of the ephemeral gully was close to 2.14 kg/(m^(2)•min),and the protective effect of ephemeral gully erosion was enhanced.When the flow rate was higher,the surface fracture of the ephemeral gully was more serious.With an increase in confluence flow rate,the ratio of erosion to deposition increased gradually,the erosion area of ephemeral gullies was expanded,and erosion depth changed minimally.In conclusion,geocell measures changed erosion patterns by altering the rill erosion/deposition ratio,converting erosion from rill erosion to sheet erosion.

THE COMPARISON OF CHINESE AND EUROPEAN STREAM RUNOFF

This paper compares stream stream runoff in China in terms of drainage basin, water balance, and regional distribution and regime of stream runoff with that in Europe. European stream runoff resources are more abundant than that of China. Europe has 28 rivers with runoff volume exceeding 10 km3, and China only has 19.But Europe has no rivers like those in China which are long andhave abundant waer volume such as Changiiang (Yangtze River) and Zhujiang. Heat conditions of the European water-abundant and water-sufficient zones are poor and their agiculture are not flourishing.In China these zones have very good heat conditions and are main farm production regions. The interannual and annual variation of stream runoff are the sane to the irrespective feedings in Europe and China.

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。

递增式连续降雨条件下典型山区坡面径流产沙水动力学特征

山区复杂的下垫面条件导致了山区小流域水文响应过程的复杂性,山区坡面作为山区小流域水文响应的基本单元,研究其不同下垫面条件下径流产沙水动力特征具有重要意义。为明晰山区坡面不同下垫面条件下径流水沙水动力特征,该研究选用官山河小流域作为研究对象,基于室内模拟递增式连续降雨试验方法,研究了坡度、土层厚度分布和土层底部透水性等山区坡面下垫面特性共同作用下的坡面径流产沙水动力学特征。结果表明:1)连续降雨条件下,雷诺数、水流剪切力和径流功率随着产流时间和雨强增加呈现增加趋势,Darcy-Weisbach阻力系数呈降低趋势。2)雨强增加使雷诺数均值和径流功率均值显著增加(P<0.05),设计雨强60、90、120 mm/h时的雷诺数均值、径流功率均值分别比30 mm/h的雷诺数均值、径流功率均值增加了130%、276%、366%和171%、328%、435%;坡度增加使水流剪切力均值和径流功率均值显著增加(P<0.05),坡度15°、25°的水流剪切力均值分别比坡度5°的增加了135%和187%,坡度15°、25°的径流功率均值分别比坡度5°的均值增加了224%和357%;土层厚度分布对阻力系数均值和土层底部透水的雷诺数均值、径流功率均值有显著影响(P<0.05),土层底部透水性仅对土层厚度分布为上薄下厚的雷诺数均值和水流剪切力均值有显著影响(P<0.05)。3)雨强是影响坡面产流产沙水动力特征的主导因素,对雷诺数的方差贡献率高达83.11%,水流剪切力主要受到雨强和坡度的影响,累计贡献率达67.64%,径流功率主要受到雨强和坡度的影响,累计贡献率达80.58%。在单一雨强条件下,坡度和土层厚度分布是影响水动力参数的主要因素,土层厚度分布和坡度的交互作用、土层底部透水性和土层厚度分布的交互作用对水动力参数也有一定影响。因此,在研究坡面产流产沙规律时,除考虑雨强和坡度外,还应兼顾考虑土层厚度分布和土层底部透水性及其交互作用的影响。该研究结果可为山区坡面复杂下垫面条件下的坡面产流产沙机理提供一定的理论支撑,并为改进山区小流域水文过程分布式模拟提供参数率定依据。

山区陡坡坡面产流产沙过程的降雨试验研究

为弄清雨强、土层厚度分布和土层底部透水性交互作用对山区陡坡坡面产流产沙过程影响规律,本文基于4种设计土槽进行室内模拟连续降雨试验。结果表明:地表径流率在连续降雨过程中呈明显波动上升趋势,侵蚀速率均值在连续降雨过程中呈现先增加后减小的趋势。地表径流率主要受到雨强的影响,方差贡献率达88.85%,侵蚀速率主要受到雨强以及土层厚度分布和雨强的交互影响,方差贡献率分别为46.13%和20.64%,土层厚度分布和土层底部透水性的交互作用对侵蚀速率也有一定影响,方差贡献率为9.21%。因此,除考虑雨强外,还应兼顾考虑土层厚度分布、土层底部透水性及其交互作用对产流产沙过程的影响。本研究可为山区坡面复杂下垫面条件下的坡面产流产沙机理提供理论支撑。

金沙江下游水库拦沙效应研究

随着众多水库建成运用,水库拦沙成为了金沙江下游减沙的主要原因。1956—2021年金沙江干流及下游支流共修建10万m^(3)以上的水库504座,总库容为687.63亿m^(3)。水库运用后,金沙江下游年径流量不存在明显变化,而年输沙量显著减小。金沙江下游出口含沙量在1998年、2013年以后大幅减小,1956—1997年平均含沙量为1.75 kg/m^(3),1998—2012年平均含沙量减小为1.22 kg/m^(3),2013—2021年平均含沙量减小为0.01 kg/m^(3)。采用双累积曲线法及水库拦沙率公式,分析水库拦沙与水土保持工程对金沙江下游减沙贡献度,结果表明:金沙江下游减沙主要由水库拦沙造成,其中1998—2012年金沙江下游年均减沙0.97亿t,水库拦沙的减沙贡献度为0.67,水土保持工程等措施的减沙贡献度为0.33;2013—2021年下游年均减沙2.43亿t,水库拦沙贡献度为0.97,水土保持工程等措施减沙贡献度为0.03。

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%。

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。

基于集中度与集中期的径流年内分配研究

借鉴年降水量年内分配的向量法,描述径流年内分配的径流集中度和集中期,尝试提出一种计算河川径流年内分配不均匀性的定量新方法。实例研究表明,用月径流量计算的集中度比径流年内不均匀系数有更高的分辨能力和敏感性,用月径流量计算的集中期对应的月份与月径流最大值出现的实际月份完全一致,径流集中度、集中期能够充分定量地表征径流在年内分配的非均匀性。

新疆和田河流域河川径流时序特征分析

根据新疆和田河流域3个测站的多年实测径流资料,从径流的年内分配和年际变化2个方面分析了和田河流域河川径流的变化特征。计算结果表明,在年内分配方面,由于径流补给来源的作用,流域径流绝大部分集中在夏季,这就使得径流年内分配不均匀系数和集中度普遍较高,而计算所得的集中期也与实测最大月径流出现的情况相吻合。在径流的年际变化方面,尽管和田河流域的年降雨量存在递增的趋势,但是由于源区高山的雪线高程上升、冰川退缩,再加上人类活动的影响越来越显著,从而导致流域的河川径流呈现微弱的下降趋势。经过周期图法分析得到,和田河流域的年径流量不存在明显的周期成分。

北江流域径流序列年内分配特征及其趋势分析

以石角站45 a的实测月径流资料为基础,研究了北江流域径流年内分配变化规律。通过计算径流年内分配不均匀性、集中程度、变化幅度等指标发现,北江径流量具有显著的洪枯季节变化,20世纪50、60年代的径流年内分配较不均匀,而70年代以来,径流年内分配较为缓和。选用db3小波函数,对各指标进行3层分解,以尺度水平3下的低频系数单支重构序列观察各指标的变化趋势,发现北江流域年内分配不均匀性指标显示为缓慢下降的趋势,尤其是70年代以后,这很可能是流域内人工水利设施对径流调节力度加大的缘故。对降雨序列的年内分配指标进行类似的分析后认为,径流不均匀系数等指标在趋势上变化的原因是流域内人工水利设施对径流的调节力度加大了。

白龙江流域上游径流年内分配变化规律分析

在气候变化与人类活动双重影响下。河川径流的年内分配特征随着发生变化。本文根据白龙江上游4个站点的实测月径流量资料，分析了年内分配不均匀性，集中程度与变化幅度等指标。结果表明：在1965～1969年、1971～1984年和2002～2006年，径流年内分配不均匀性较强：白龙江上游集中度较小。集中度随时间的增加均呈现降低趋势。流域自上游向下游，在不同年代集中期均表现为逐渐缩短的变化趋势。Cm、Cm-max和AR随时间增加而减小，Cm-man刊。随时间增加而增大。总体上看，随着时间的推移，白龙江上游径流年内分配不均匀性越来越低，逐渐由不均匀向相对均匀转变。