Flow Distribution,Flooding and Water Engineering Measures in the Volga-Akhtuba Floodplain Region: 2 Modeling

The results of studying the hydrological regime ofthe Volga-Akhtuba floodplain based on the joint analysis of observation and hydrodynamic modeling data are presented. The calculated hydrological characteristics are compared with observational data. The areas and boundaries of zones flooded by the water flow from the Akhtuba and Volga rivers are estimated. The efficiency of water engineering activities aimed at the improvement of flooding conditions is analyzed for the most problematic part of the Volga-Akhtuba floodplain.     

Estimation of transformation of flood runoff hydrographs and water stages in the Lower Volga and its delta

A system of hydrographs’ quantitative parameters for the flood discharges and stages in the Lower Volga River and its delta was developed. Water releases from the Volzhskaya Hydropower Plant and floods in the upper sections of the Volga River delta caused by those releases were identified and grouped in accordance with their water content; their parameters were computed for the entire period of the runoff managing (i.e., since 1961). In addition, parameters of typical hydrographs, which were averaged for different categories of water content, were computed and their graphical models were plotted. Quantitative and qualitative estimates of changes in shape of the discharge hydrographs in the Lower Volga were obtained for different flood types, while for the water stage hydrographs in the Lower Volga and its delta, only quantitative estimation was carried out.     

Spatiotemporal Changes in Extreme Runoff Characteristics for the Volga Basin Rivers

Long-term changes in peak spring runoff and daily minimum winter and summer-autumn runoff in the Volga River basin are analyzed based on observational data from 94 gaging stations. It is revealed that climate changes in the basin during the period from the late 1970s till the middle of the 1980s led to the significant increase in minimum discharge, but maximum runoff changed ambiguously. The regions with the disturbed uniformity of the series of extreme values of river runoff are identified. Changes in the values of high runoff, above the 10% probability, and low runoff, below the 90% probability, are analyzed for current climate conditions. Under nonstationary conditions, it is recommended to assess the probability characteristics of extreme runoff with compound distribution curves or based on the Bayesian approach.     

Computation and prediction of the flood runoff of the Eastern Caucasus rivers

Analysis of observational data of the average monthly discharges, air temperatures, and precipitation totals collected at about 100 hydrological and meteorological stations before 2005 revealed that precipitation fallen on the Eastern Caucasus river basins in winter and spring plays the principal role in formation of floods that are observed in the period from April to June. The precipitation and runoff variability over the territory and altitudinal zones was studied and generalized. The hydrograph decomposition and the rivers classification according to their sources of feeding in the flooding period were performed. Analysis of correlation between the flood flow and winter and spring precipitation allowed obtaining reliable multiple regression equations that are suitable for computation and forecasting of the flood flow.     

红水河汛期径流与印度洋海温异常的关系

使用1951—2014年广西河池市红水河龙滩站的月流量和同期海温、500 hPa位势高度、850 hPa矢量风资料,基于相关分析、EOF分析和合成分析,研究了红水河汛期流量与印度洋海温异常的关系,以及印度洋海温异常影响红水河流量的物理机制。结果表明,印度洋海温距平分布的三种模态,包括前期夏季印度洋海温距平EOF1_6—8、EOF1_2—4、印度洋海温距平EOF1_2—4和EOF3_2—4,与红水河汛期流量显著相关。用这三个模态的时间系数、龙滩站前期4—5月平均流量和南印度洋2、3和4月偶极子指数可以很好地模拟龙滩站汛期流量,因此,它们可以作为红水河径流预测的物理因子。印度洋海温异常影响红水河汛期流量的途径可以概括为,印度洋海温冷水年,冷异常可在四个季节持续。春季冷海温可使北半球春季南支气流上小槽波动强烈,南支槽加强,水汽输送显著增强;夏季可显著增强夏季风气流,使更多的水汽输送到红水河增大径流量;秋季和冬季,印度洋的冷海水减弱了北半球冬季环流形势,诱使西北太平洋水汽向中国东部地区输送,使红水河有更多的水汽汇集增大龙滩站流量。反之,印度洋海温暖水年时,四个季节的海温持续增暖,使北半球中纬度低气压系统变得不活跃,冬季形势进入早、而结束晚,中国东部受干燥气流控制时间长,春季和夏季副热带高压增强,同时,夏季风减弱,水汽输送较少,使汛期红水河流量减小。      

Present-day variations of the minimum runoff of the Volga basin rivers

Carried out is the analysis of stationarity of minimum runoff series in summer and winter for the Volga basin rivers. Two conditionally homogeneous periods are singled out within the temporal variations of these characteristics, and the date of their change varies throughout the territory of the basin. The considerable rise in air temperature in winter on the whole territory of the Volga basin is demonstrated as a result of the analysis of meteorological parameters. The relationship between runoff variations and wintertime temperature variations is proposed for predicting the minimum runoff. The distribution of minimum values of runoff is computed using this dependence and the forecast method based on the sum of distributions.     

青藏高原热力状况与四川盆地汛期降水的联系

应用高原积雪日数和高原气温、四川盆地逐月降水量资料,应用ＳＶＤ等方法,探讨高原热力状况分布异常与四川盆地汛期降水分布的联系。分析结果表明,高原积雪日数场分布特征是以巴颜喀拉山和念青唐古拉山为中心。该区域冬季积雪日数异常与川中盆地汛期干旱有相当好的联系。春季青藏高原北部和祁连山的温度场的大范围异常则与川西的洪涝和川东的干旱均有较好的相关,均可作为四川降水长期预报综合考虑的重要参考因子。一般而言,积雪     

Hydrochemical and Hydrological Conditions in the Ural River Lower Reaches and in the Caspian Sea Mouth Region at the Beginning of the Spring Flood

The study presents data of hydrophysical observations and the results of studying the chemical composition of water and suspended particulate matter obtained in April of 2016 and 2017 during the complex studies in the Ural River lower reaches and in the Caspian Sea region adjoining the river mouth. It is revealed that the chemical composition of river runoff varied greatly not only from year to year but also within the period of field studies that may be explained by the water inflow from different parts of the river catchment during the spring flood.     

干旱气候对青海地表水资源影响的研究

通过分析近38年青海省主要河流径流量及其流域降水、气温的变化趋势,研究了干旱气候对青海地表水资源的影响。结果表明,内陆河多为高山冰雪融水和雨水混合补给型河流,外流河多为以雨水补给为主的河流;青海地表水资源呈减少趋势,其减少趋势进入90年代后尤为明显;气温和降水是影响青海地表水资源的主要气候因子,其中气温升高加剧了流域蒸发量的增大和干旱影响,减少了地表径流量;而90年代以来降水量的减少特别是汛期降水量的减少直接影响到径流量的减少。     

青海地表水资源的变化及影响因子

通过分析近３８年青海省主要河流径流量及其流域降水、气温的变化趋势,着重研究了干旱气候对青海地表水资源的影响。结果表明,内陆河多为高山冰雪融水和雨水混合补给型河流,外流河多为以雨水补给为主的河流;青海地表水资源呈减少趋势,其减少趋势进入９０年代后尤为明显;气温和降水是影响青海地表水资源的主要气候因子,其中气温升高加剧了流域蒸发量的增大和干旱影响,减少了地表径流量;而９０年代以来降水量的减少特别是汛期降水量的减少直接影响到径流量的减少。     

Changes of Accumulated Temperature, Growing Season and Precipitation in the North China Plain from 1961 to 2009

Using the high-quality observed meteorological data, changes of the thermal conditions and precipitation over the North China Plain from 1961 to 2009 were examined. Trends of accumulated temperature and negative temperature, growing season duration, as well as seasonal and annual rainfalls at 48 stations were analyzed. The results show that the accumulated temperature increased significantly by 348.5℃ day due to global warming during 1961-2009 while the absolute accumulated negative temperature decreased apparently by 175.3℃ day. The start of growing season displayed a significant negative trend of -14.3 days during 1961- 2009, but the end of growing season delayed insignificantly by 6.7 days. As a result, the length of growing season increased by 21.0 days. The annual and autumn rainfalls decreased slightly while summer rainfall and summer rainy days decreased significantly. In contrast, spring rainfall increased slightly without significant trends. All the results indicate that the thermal conditions were improved to benefit the crop growth over the North China Plain during 1961-2009, and the decreasing annual and summer rainfalls had no direct negative impact on the crop growth. But the decreasing summer rainfall was likely to influence the water resources in North China, especially the underground water, reservoir water, as well as river runoff, which would have influenced the irrigation of agriculture.     

Indicators of Climate Warming in Minnesota: Lake ICE Covers and Snowmelt Runoff

Records of hydrologic parameters, especially those parameters that are directly linked to air temperature, were analyzed to find indicators of recent climate warming in Minnesota, USA. Minnesota is projected to be vulnerable to climate change because of its location in the northern temperate zone of the globe. Ice-out and ice-in dates on lakes, spring (snowmelt) runoff timing, spring discharge values in streams, and stream water temperatures recorded up to the year 2002 were selected for study. The analysis was conducted by inspection of 10-year moving averages, linear regression on complete and on partial records, and by ranking and sorting of events. Moving averages were used for illustrative purposes only. All statistics were computed on annual data. All parameters examined show trends, and sometimes quite variable trends, over different periods of the record. With the exception of spring stream flow rates the trends of all parameters examined point toward a warming climate in Minnesota over the last two or three decades. Although hidden among strong variability from year to year, ice-out dates on 73 lakes have been shifting to an earlier date at a rate of −0.13 days/year from 1965 to 2002, while ice-in dates on 34 lakes have been delayed by 0.75 days/year from 1979 to 2002. From 1990 to 2002 the rates of change increased to −0.25 days/year for ice-out and 1.44 days/year for ice-in. Trend analyses also show that spring runoff at 21 stream gaging sites examined occurs earlier. From 1964 to 2002 the first spring runoff (due to snowmelt) has occurred −0.30 days/year earlier and the first spring peak runoff −0.23 days/year earlier. The stream water temperature records from 15 sites in the Minneapolis/St Paul metropolitan area shows warming by 0.11^∘C/year, on the average, from 1977 to 2002. Urban development may have had a strong influence. The analysis of spring stream flow rates was inconclusive, probably because runoff is linked as much to precipitation and land use as to air temperature. Ranking and sorting of annual data shows that a disproportionately large number of early lake ice-out dates has occurred after 1985, but also between 1940 and 1950; similarly late lake ice-in has occurred more frequently since about 1990. Ranking and sorting of first spring runoff dates also gave evidence of earlier occurrences, i.e. climate warming in late winter. A relationship of changes in hydrologic parameters with trends in air temperature records was demonstrated. Ice-out dates were shown to correlate most strongly with average March air temperatures shifting by −2.0 days for a 1^°C increase in March air temperature. Spring runoff dates also show a relationship with March air temperatures; spring runoff dates shift at a rate of −2.5 days/1^°C minimum March air temperature change. Water temperatures at seven river sites in the Minneapolis/St Paul metropolitan area show an average rise of 0.46^°C in river temperature/1^°C mean annual air temperature change, but this rate of change probably includes effects of urban development. In conclusion, records of five hydrologic parameters that are closely linked to air temperature show a trend that suggests recent climate warming in Minnesota, and especially from 1990 to 2002. The recent rates of change calculated from the records are very noteworthy, but must not be used to project future parameter values, since trends cannot continue indefinitely, and trend reversals can be seen in some of the long-term records.     

Estimates of continental-scale soil wetness and comparison with the soil moisture data of Mintz and Serafini

 Soil wetness, in both its global distribution and the seasonal change, has been mainly estimated by the water balance approach using the bucket model which regards the soil wetness as soil moisture. The soil moisture data of Mintz and Serafini is one of the representatives examples, however, this method has problems since it does not incorporate the effects of flooding, snow accumulation on the ground, and so on. In this study, we use the Amazon and Volga river basin to carry out a case study to evaluate these problems. In the Amazon river basin, the annual range of the entire terrestrial water storage, about 400 mm, can be mainly explained by the rising and falling of the water level, and flooding around river channels, although soil moisture data of Mintz and Serafini is almost constant throughout the year. In the Volga river basin, snow accumulates on the ground producing 80 mm of water equivalent during winter, however the soil moisture data of Mintz and Serafini is almost saturated in winter. Received: 30 October 1996 / Accepted: 4 June 1997     

Assessing the Impact of Climate Change on Water Supply and Flood Hazard in Ireland Using Statistical Downscaling and Hydrological Modelling Techniques

Estimates are made of changes in effective runoff at a high spatial resolution for the island of Ireland under different climate change scenarios. The first part of the investigation examines changes in annual and seasonal effective runoff for the whole land area of Ireland. The rainfall-runoff model HYSIM is used to carry out the hydrological simulations. The output from the HadCM3 Global Climate Model (GCM) is downscaled using statistical techniques to provide precipitation and evaporation data at a 10 km × 10 km resolution; this data is then used to drive the HYSIM model. Simulations are carried out for each of the 825 10 km × 10 km grid cells covering Ireland for the baseline period (1961–1990) and two future scenarios; 2041–2070 and 2061–2090. Parameter values are derived for each square using data from the Soil Survey of Ireland and the CORINE land use database and validation is carried out for selected catchments. The results of these simulations indicate a decrease in annual runoff that is most marked in the east and southeast of the country, whereas an increase is likely for the extreme northwest. The reduction in effective runoff for the east of the country is particularly marked during the summer months. It is these areas that have highest population density and also where greatest population growth is likely to occur. During the winter months an increase in effective runoff is suggested for the western half of country which could have implications for flood frequency, as well as the extent and duration of winter flooding.     

Changes of Accumulated Temperature, Growing Season andPrecipitation in the North China Plain from 1961 to 2009

Using the high-quality observed meteorological data,changes of the thermal conditions and precipitation over the North China Plain from 1961 to 2009 were examined.Trends of accumulated temperature and negative temperature,growing season duration,as well as seasonal and annual rainfalls at 48 stations were analyzed.The results show that the accumulated temperature increased significantly by 348.5℃ day due to global warming during 1961 2009 while the absolute accumulated negative temperature decreased apparently by 175.3℃ day.The start of growing season displayed a significant negative trend of-14.3 days during 1961-2009,but the end of growing season delayed insignificantly by 6.7 days.As a result,the length of growing sea.son increased by 21.0 days.The annual and autumn rainfalls decreased slightly while summer rainfall and summer rainy days decreased significantly.In contrast,spring rainfall increased slightly without significant trends.All the results indicate that the thermal conditions were improved to benefit the crop growth over the North China Plain during 1961-2009,and the decreasing annual and summer rainfalls had no direct negative impact on the crop growth.But the decreasing summer rainfall was likely to influence the water resources in North China,especially the underground water,reservoir water,as well as river runoff,which would have influenced the irrigation of agriculture.     

近55年广西融水县降水气候特征分析

利用融水县气象站1959-2013年的降水资料,采用数理统计和线性倾向估计分析方法,分析了融水县降水分布特征及其变化规律。结果表明：融水县降水分配不均,主要集中在4-8月,6月最多,5月次之;年暴雨日数6.9d,暴雨持续时间多为1d,最长4d;近55年来融水县年降水量和汛期（4-9月）降水量均呈减少趋势,每10年分别减少16mm和6mm,而主汛期（5-8月）的降水量却呈增多趋势,每10年增加13mm,这预示着融水县未来降水可能更趋于集中在主汛期（5-8月）,发生洪涝灾害的几率可能增多。此外,一日最大降水量呈增多趋势,预示未来降雨强度可能增大;春、秋季的降水量呈减少趋势,提示未来发生春旱、秋旱的几率可能增多。     

Long-term variations of elements of hydrometeorological regime of the Rybinsk Reservoir

Variations of hydrometeorological variables of the Rybinsk Reservoir area from 1947 to 2005 are analyzed. A special attention is given to the global warming period started since 1976. It is shown that the intensity of air temperature increase on the reservoir shore during recent 30 years made up 0.46–0.56°C/10 years. The maximum increase in the water temperature at shore stations and in the surface layer was registered in July at an increase rate of 0.7–1.2°C/10 years. The change in climate conditions resulted in the increase in low-water runoff, decrease in snowmelt flood volumes, and shift in the time of snowmelt flood start.     

Analysis of formation and forecast of spring snowmelt flood runoff in forest and forest-steppe basins of Siberian rivers

Popov’s infiltration-capacitive model of the spring runoff, including the computation of the runoff losses due to evaporation in the period of snow melting and losses due to evaporation and absorption in the period of exhaustion of the sheet inflow into the channel net, is used. Equations to forecast the spring snowmelt flood runoff, taking account of the frozen soil melting, are derived. The method of estimation of their parameters on the base of the joint use of linear regression and optimization methods is realized. It is demonstrated that factors of the autumn moistening and freezing of soils of basins in the beginning of winter influence the spring runoff losses. The integrated index of the initial state of the basin, taking account of mentioned factors, is proposed.     

信江流域洪峰期水位预测方法初探

采用2003～2006年5～9月水位及同期日雨量资料,以信江流域为例,利用逐步回归方法对洪峰期内梅港的水位与前期各气象站日降水量的关系进行了研究,并建立洪峰水位预测模型。结果表明:该模型有一定的预测准确率;各站降水产生的地表径流在24 h之内就能影响到下游的梅港水文站水位;距离梅港水文站最近的气象站前2 d的24 h降水产生的壤中流和地下径流对梅港洪峰期水位也有显著影响;此外,当梅港水位位于21 m之上时拟合绝对误差明显增大,当水位峰值小于23 m时,其拟合值偏大,当水位峰值大于23 m时,其拟合值偏小。     

基于HBV模型的太子河流域致洪临界雨量的确定

以太子河流域为研究区域,基于流域内的气象水文数据、数字高程模型及土地利用等资料,采用HBV水文模型对流域的水文过程进行模拟,通过对模型参数的率定与验证,评估了HBV模型在该流域径流模拟的适用性,确定了适合太子河流域的最优化参数,结合水位-流量关系曲线,推算太子河流域不同等级洪水致洪临界雨量。结果表明: HBV模型对太子河流域的径流模拟效果较好,率定期与验证期Nash效率系数与确定性系数均超过0.60,模型中积雪和融雪模块(CFR)、土壤含水量计算模块(BETA)与响应模块(KUZ2、UZ1、PERC)中的这些参数最为敏感,模型基本模拟出了洪水对降水的响应过程。通过建立的HBV水文模型,结合小林子水文站的水位-流量关系曲线,以警戒水位、保证水位作为不同等级洪水的判别条件,推算得到了不同起始水位下太子河流域动态临界雨量指标,临界雨量随起始水位的升高而有所减小。