Experience in monitoring channel deformations on rivers with broad flood plains (as exemplified by the Kerzhenets river)

Presented are the results of a five-year (2001-2005) monitoring of deformations of the Kerzhenets river channel in its lower part. The concave-bank caving observations were made for three free bights compose d of sand and loamy sand: the steep segmental, segmental developed and segmental gently sloping blights.     

Spatiotemporal variability of permafrost degradation on the Qinghai-Tibet Plateau

Based on data from six meteorological stations in the permafrost regions, 60 boreholes for long-term monitoring of permafrost temperatures, and 710 hand-dug pits and shallow boreholes on the Qinghai-Tibet Plateau (QTP), the spatiotemporal variability of permafrost degradation was closely examined in relation to the rates of changes in air, surface, and ground temperatures. The decadal averages and increases in the mean annual air temperatures (MAATs) from 1961–2010 were the largest and most persistent during the last century. MAATs rose by 1.3 °C, with an average increase rate of 0.03 °C/yr. The average of mean annual ground surface temperatures (MAGSTs) increased by 1.3 °C at an average rate of 0.03 °C/yr. The rates of changes in ground temperatures were ?0.01 to 0.07 °C/yr. The rates of changes in the depths of the permafrost table were ?1 to +10 cm/yr. The areal extent of permafrost on the QTP shrank from about 1.50×10⁶ km² in 1975 to about 1.26×10⁶ km² in 2006. About 60% of the shrinkage in area of permafrost occurred during the period from 1996 to 2006. Due to increasing air temperature since the late 1980s, warm (>?1 °C) permafrost has started to degrade, and the degradation has gradually expanded to the zones of transitory (?1 to ?2 °C) and cold (相似文献   

Spatiotemporal analysis of climate variability impacts on malaria prevalence in Ghana

There are conflicting results from research on the impacts of temperature and rainfall on malaria prevalence. As a result predicting malaria prevalence still remains a challenge. Generating relevant information on the role of temperature, rainfall, and humidity on malaria prevalence at different geographic scales is critical to efforts to combat the burden of prevalence. For better understanding of climate variability and the impacts on malaria prevalence, this study examined the varying spatial and seasonal distribution in malaria prevalence over time in Ghana. We used trajectory and time series analyses for temporal distribution and conducted GIS-based analyses of the spatial distribution of yearly malaria incidence and climate variables. We observed that the national annual malaria incidence has increased. Considerable inter-annual variations were also detected in the intensity of incidence across regions characterized with varying rainfall and temperature regimes. The results indicated that temperature and humidity have some association with malaria prevalence in Ghana. Although annual rainfall in the model was found to be less significant, there is evidence of rainfall as a predictor of malaria in Ghana. These findings show that public health resource allocations should focus on the areas with the highest malaria risk in Ghana.     

Prediction of alluvial channel pattern of perennial rivers

Purely braided, meandering and straight channels can be considered as end-members of a continuum of alluvial channel patterns. Several researchers have succeeded in separating channel patterns in fields defined by flow related parameters. However, the discriminators of the principal channel patterns derived from these diagrams all require some a priori knowledge of the channel geometry. In this paper a method is presented which enables prediction of the equilibrium conditions for the occurrence of braided and high sinuosity meandering rivers in unconfined alluvial floodplains. The method is based on two, almost channel pattern independent, boundary conditions: median grain size of the river bed material, and a potential specific stream power parameter related to bankfull discharge or mean annual flood and valley gradient. This can be regarded as a potential maximum of the available flow energy corresponding to the minimum sinuosity condition, P = 1. Based on an analysis of 228 datasets of measurement sites along rivers from many parts of the world an independent discriminating function was found that separates the occurrence of braided rivers and meandering rivers with P > 1.5. The function applies to equilibrium conditions of rivers that neither incise nor show rapid aggradation, with a bankfull or mean annual flood discharge above 10 m³/s and a median bed material grain size between 0.1 and 100 mm.     

Influence of channel reconfigurations on the development of confluence nodes of rivers

Using the confluence nodes of broad-floodplain rivers as an example, we examine the different variants of effects of channel deformations (channel meandering of the main river and its tributary, formation of forks, and shift of meander bars) upon their configuration and reconfiguration across time. We demonstrate the diversity of these effects even where the deformations themselves are of the same type. Problems of further investigations are formulated.     

Comparative analysis of channel processes on mountain,semi-mountain and plain rivers

The mechanisms and the specific character of flow-channel interaction and sediment transport that constitute the essence of river channel processes, vary over a wide range according to the flow rate of the rivers, their water regime, flow kinematics, the value of longitudinal gradient, and to the grain size and runoff of riverbed-forming sediments. Furthermore, the longitudinal gradient of a river is as important an energy characteristic as is the water flow rate, coupled with it, determines the capacity and character of a stream. Therefore the hydrological regime, varying over a wide range according to the longitudinal gradient, produces a variety of transport conditions for riverbed-forming sediments and – through them – the form of manifestation of channel processes.     

Characteristics of channel processes in brooks and the smallest plain rivers

We characterize the main forms of manifestation of channel processes on first-order streams that have not been studied previously from this standpoint. The main morphological features of small streams are described, a typization of channel processes is provided, and differences from processes and forms of their manifestation in channels of larger rivers are identified.     

Engineered channel controls limiting spawning habitat rehabilitation success on regulated gravel-bed rivers

In efforts to rehabilitate regulated rivers for ecological benefits, the flow regime has been one of the primary focal points of management strategies. However, channel engineering can impact channel geometry such that hydraulic and geomorphic responses to flow reregulation do not yield the sought for benefits. To illustrate and assess the impacts of structural channel controls and flow reregulation on channel processes and fish habitat quality in multiple life stages, a highly detailed digital elevation model was collected and analyzed for a river reach right below a dam using a suite of hydrologic, hydraulic, geomorphic, and ecological methods. Results showed that, despite flow reregulation to produce a scaled-down natural hydrograph, anthropogenic boundary controls have severely altered geomorphic processes associated with geomorphic self-sustainability and instream habitat availability in the case study. Given the similarity of this stream to many others, we concluded that the potential utility of natural flow regime reinstatement in regulated gravel-bed rivers is conditional on concomitant channel rehabilitation.     

Sediment discharge variability in Arctic rivers: implications for a warmer future

A new model for predicting the sediment flux in ungauged river basins is applied to 46 Arctic to sub-Arctic rivers. The model predicts the preanthropogenic flux of sediment to within a factor of 2, across four orders of magnitude in basin area and run-off. The model explains for the first time why Arctic rivers carry so little sediment when compared at the global scale. Sensitive to drainage basin temperature, the model is used to examine the impact of a climate warming scenario on the loads of high latitude rivers. As the Arctic warms, rivers will carry increased sediment loads, similar to more temperate rivers. For every 2°C warming, the model predicts a 22% increase in the flux of sediment carried by rivers. For every 20% increase in water discharge there will be a 10% increase in sediment load. The model also aids the interpretation of palaeoclimate records obtained from Arctic continental margins.     

1970-2015年秦岭南北气温时空变化及其气候分界意义

基于秦岭南北70个气象站点观测资料,辅以极点对称模态分解方法（ESMD）,对秦岭南北近期气温时空变化特征进行分析,进而以日平均温≥ 10 ℃积温天数为主要指标,以1月0 ℃等温线变化为辅助指标,探讨秦岭山脉的气候分界意义。结果表明：① 1970-2015年秦岭南北气温变化具有同步性,呈现出“非平稳、非线性、阶梯状”的增暖过程,变化阶段可分为：1970-1993年为低位波动期、1994-2002年为快速上升期、2003-2015年为增温停滞期;② ESMD信息分解结果表明,秦岭南北气温变化以年际波动为主导,并未呈现出明显的线性增暖趋势;③ 在空间上,秦岭南北气温趋势呈现“同步增温,南北分异”的响应特征,即秦岭以北地区空间增温具有一致性,秦岭以南地区则呈现“西乡—安康盆地交界”、“商丹盆地”两个低值中心;④ 在气候变暖背景下,秦岭作为气候分界线的作用依然明显,但是南北响应方式存在差异。其中,秦岭以南,北亚热带北界沿山地“垂直上升”,汉江谷地热量资源逐年增加;秦岭以北,尽管以城市带为中心的增温区不断延展,但是冷月气温偏低的格局并未改变。     

陕北黄土高原区极端降水时空变化特征及其影响因素

基于1970—2017年逐日降水数据,辅以趋势分析、空间分析和小波相干等气候诊断方法,对陕北黄土高原区极端降水时空变化特征进行分析,探讨不同海区海温异常与降水变化的响应关系。结果表明：① 1970—2017年,陕北地区气温波动上升,降水增加,半干旱界线明显向西北方向移动;② 1970—2017年,陕北地区降水呈现极端化。具体表现为,弱降水日数减少,强降水日数增加,降水持续时间呈现破碎化,1日最大降水量、5日最大降水量和降水强度均表现出显著的上升趋势;③ 在影响因素上,陕北地区极端降水变化受赤道太平洋中西部海温影响明显于东部,受赤道太平洋北侧影响明显于南侧,受海温年代周期变化影响（14~16a）明显于中长期周期（4~8a）。同时,NINO W区可作为区域极端降水响应的关键海区。当NINO W区海温异常偏高时,陕北地区降水普遍偏高,降水强度和持续时间增加,易发生雨涝灾害。     

Morphodynamic river processes and techniques for assessment of channel evolution in Alpine gravel bed rivers

Over the past 10 years many restoration projects have been undertaken in Austria, and river engineering measures such as spur dykes and longitudinal bank protection, which imposed fixed lateral boundaries on rivers, have been removed. The EU-Life Project “Auenverbund Obere Drau” has resulted in extensive restoration on the River Drau, aimed to improve the ecological integrity of the river ecosystem, to arrest riverbed degradation, and to ensure flood protection. An essential part of the restoration design involved the consideration of self-forming river processes, which led to new demands being imposed on river management.This paper illustrates how model complexity is adapted to the solution and evaluation of different aspects of river restoration problems in a specific case. Point-scale monitoring data were up-scaled to the whole investigation area by means of digital elevation models, and a scaling approach to the choice of model complexity was applied. Simple regime analysis methods and 1-D models are applicable to the evaluation of long-term and reach-scale restoration aims, and to the prediction of kilometre-scale processes (e.g. mean river bed aggradation or degradation, flood protection). 2-D models gave good results for the evaluation of hydraulic changes (e.g. transverse flow velocities, shear stresses, discharges at diffluences) for different morphological units at the local scale (100 m–10 m), and imposed an intermediate demand on calibration data and topographic survey. The study shows that complex 3-D numerical models combined with high resolution digital elevation models are necessary for detailed analysis of processes (1 m–0.01 m), but not for the evaluation of the restoration aims on the River Drau. In conclusion, model choice (complexity) will depend on both lower limits (determined by the complexity of processes to be analysed) and upper limits (field data quality and process understanding for numerical models).     

Predicting changes in alluvial channel patterns in North-European Russia under conditions of global warming

Global climate change may have a noticeable impact on the northern environment, leading to changes in permafrost, vegetation and fluvial morphology. In this paper we compare the results from three geomorphological models and study the potential effects of changing climatic factors on the river channel types in North-European Russia. Two of the selected models by Romashin [Romashin, V.V., 1968. Variations of the river channel types under governing factors, Annals of the Hydrological Institute, vol. 155. Hydrometeoizdat, Leningrad, pp. 56–63.] and Leopold and Wolman [Leopold, L.B., Wolman, M.G., 1957. River channel pattern: braided, meandering and straight, Physiographic and hydraulic studies of rivers. USA Geological Survey Professional Paper 252, pp. 85–98.] are conventional QS-type models, which predict the existence of either multi-thread or single-tread channel types using data on discharge and channel slope. The more advanced model by Van den Berg [Van den Berg, J.H., 1995. Prediction of alluvial channel pattern of perennial rivers. Geomorphology 12, 259–270.] takes into account the size of the sediment material.We used data from 16 runoff gauges to validate the models and predict the channel types at selected locations under modern and predicted for the future climatic conditions. Two of the three models successfully replicated the currently existing channel types in all but one of the studied sites. Predictive calculations under the hypothetical scenarios of 10%, 15%, 20% and 35% runoff increase gave different results. Van den Berg's model predicted potential transformation of the channel types, from single- to multi-thread, at 4 of 16 selected locations in the next few decades, and at 5 locations by the middle of the 21st century. Each of the QS-type models predicted such transformation at one site only.Results of the study indicate that climatic warming in combination with other environmental changes may lead to transformation of the river channel types at selected locations in north-western Russia. Further efforts are needed to improve the performance of the fluvial geomorphological models and their ability to predict such changes.     

游荡性河流演变规律研究进展及其河型归属探讨

游荡性河道在中国广泛分布,其中以黄河下游上段最为典型,但关于游荡性河型的归属问题尚存在很大争议,国际上多将游荡性河流归属为辫状河型。本文以黄河下游游荡性河道为典型案例,系统总结了游荡性河流的演变特征、主要影响因素和形成机理,并从定义、成因、特征及河道形成过程方面,将游荡与辫状河型的异同点进行对比分析。得到以下启示：游荡性河型是一种重要的河道型态,与辫状河型在许多方面存在较明显差异。特别是游荡河型主要发育于能量小于输沙需求的环境,因而形态呈现不稳定特性,但辫状河型不仅出现在能量较多的环境,而且也常在能量较小的环境中出现,因而一部分具有稳定形态,另一部分则表现出不稳定的特性,因此,有必要对游荡性河道和辫状河道给予区分。最后对未来研究进行了展望,提出应重视河型形成的内在机理,对能量理论进行发展及深化,进一步系统性评价游荡性河道与辫状河道的异同性,以解决游荡性河道的河型归属问题。     

1995-2012年中国突发性环境污染事件时空演化特征及影响因素

利用ESDA空间统计分析方法和Matlab空间面板计量模型,对1995-2012年中国各地区发生的环境污染事件的时空演化特征和影响因素进行分析。结果表明:环境污染事件呈先动态增长后逐渐下降的趋势,水污染和大气污染事件是主要事故类型;环境污染事件发生的高频风险区域亦在逐渐减少,东南沿海及四川、湖南等中西部区仍有局部集聚的态势;1995-2000年中国的环境污染事件总体呈随机分布状态,2001年后则开始呈现集聚的特征;Moran散点图表明,局部的空间集聚先增强后减弱,环境污染事件近年来集中在泛长三角地区,高高地区为江浙沪;环境污染事件的重心转移方向主要为西南和东北,两个快速转移时期分别为1998-2001和2004-2007年,这与区域的产业转移和高负荷的污染排放压力有关;环境污染事件的发生与污染物的达标排放和控制、经济发展阶段及环境治理投入、环境监管能力、空间效应等因素有关。空间效应主要体现在空间邻近效应和空间溢出效应。未来应注重环境污染事故的区域联防联控,制定若干跨界污染事故的应急响应联动机制及环境污染区域联防联控机制。     

1960-2016年秦岭—淮河地区热浪时空变化特征及其影响因素

基于134个气象站点1960-2016年逐日最高温和相对湿度数据,辅以趋势分析、空间分析和相关分析等方法,对秦岭—淮河地区热浪时空变化特征进行分析,探讨了赤道东太平洋海温异常与热浪变化的相关关系。结果表明：①近57年秦岭—淮河地区热浪呈现“非线性、非平稳和阶段性”的变化过程,年代变化可分为3个阶段：1960-1972年热浪呈现东西分异,分界线大致位于112°E,以东地区热浪异常偏多,以西地区则“高低交替”波动;1973-1993年热浪维持“低位波动”,并在20世纪80年代中期呈现快速增加;1994-2016年,关中平原、秦巴山区、巫山山区和四川盆地热浪维持“高位波动”,黄河下游、淮河平原和长江下游热浪则经历从“相对偏多”向“相对偏少”的转变;②在影响因素方面,最高温波动变化是秦岭—淮河地区热浪频次年代变化的主导因素,相对湿度变化的影响相对较弱;③近57年来关中平原热浪年代变化与赤道太平洋西部海温异常关系更为密切,长江流域与东部海温异常关系更为密切;对于黄河下游和秦巴山区的热浪变化与不同分区赤道太平洋海温异常关系均较弱。     

Spatiotemporal variability of cultivable microfungal communities inhabiting a playa area in the western Negev Desert,Israel

The soil dilution plate method was used to examine spatiotemporal changes in microfungal communities inhabiting the playa and interdune areas in the western Negev Desert, Israel. Soil samples were collected from the 0–50 cm depth at 10 cm intervals at both habitats during the wet and dry seasons of 2010. Forty-six species belonging to 31 genera were identified, 14 and 12 species were common to both habitats during the wet and dry seasons. The colony-forming units (CFUs) ranged from 75 to 4875 and from 500 to 6925 CFU g⁻¹ dry soil at the playa and interdune, respectively. More diverse species and higher microfungal density were recorded during the wet season compared to the dry season at both habitats, and the microfungal communities inhabiting the playa were characterized by lower species diversity and CFU compared with the interdune regardless of soil depth and sampling season. With the increase in soil depth, decreasing trends were found in both species diversity and CFU throughout the study period, especially in the playa soils. Generally, Cladosporium cladosporioides, Alternaria alternata, Ulocladium atrum, and Fusarium spp. were widespread at the playa with high relative abundance, as were Penicillium and Aspergillus spp. at both habitats.     

The factors of interannual variability in minimum winter dis-charge of the rivers in the upper part of the Lena basin

We investigate the formation of interannual variability in minimum winter discharge for a number of rivers in the upper part of the Lena basin depending on the eventual factors that are responsible for this variability. The study revealed the most important variables which can be used as predictors of the discharge parameters under consideration. We have constructed the regression models for predicting the parameters of minimum winter discharge with a 1-4-month predictability.     

秦岭—淮河南北供暖格局变化及其影响因素

基于秦岭—淮河南北及其周边196个气象站点观测资料,构建实际和动态供暖指数,对中国南北过渡带供暖格局变化进行分析,并探讨冬季北极涛动（AO）异常与供暖效率的响应关系。结果表明：① 固定供暖策略下,1960-2016年秦岭—淮河南北实际供暖能耗偏高,呈现“南多北少,西低东高”的变化特征,且低纬度地区供暖需求下降信号早于高纬度;② 对比区域变暖前后,秦岭—淮河南北冬季供暖能耗1960-1990年和1990-2016年两阶段空间特征,发现“整体南高北低,北部东高西低”的格局并未发生变化,供暖南北波动界线依然维持在秦岭山脉—淮河平原中部;③ AO强弱波动与区域冬季供暖能耗具有明显的时空响应关系,是影响中国南北过渡带供暖格局变化的重要因素。当AO负相位时,除四川盆地和巫山山区之外,秦岭—淮河南北其他区域实际供暖能耗明显下降,特别是淮河平原和长江下游的过渡地带响应尤为明显,未来应该有针对性制定气候适应对策。     

亚洲国际河流研究进展

1 General situation Entering the 21st century, resource and environmental diplomacy is regarded as a new element for establishing future international patterns of cooperation. Transboundary resources and environmental issues in international river basins …