Hydrological trends and the evolution of catchment research in the Alptal valley,central Switzerland     

Manfred Stähli  Jan Seibert  James W. Kirchner  Jana von Freyberg  Ilja van Meerveld 《水文研究》2021,35(4):e14113

When the observation of small headwater catchments in the pre-Alpine Alptal valley (central Switzerland) started in the late 1960s, the researchers were mainly interested in questions related to floods and forest management. Investigations of geomorphological processes in the steep torrent channels followed in the 1980s, along with detailed observations of biogeochemical and ecohydrological processes in individual forest stands. More recently, research in the Alptal has addressed the impacts of climate change on water supply and runoff generation. In this article, we describe, for the first time, the evolution of catchment research at Alptal, and present new analyses of long-term trends and short-term hydrologic behaviour. Hydrometeorological time series from the past 50 years show substantial interannual variability, but only minimal long-term trends, except for the ~2°C increase in mean annual air temperature over the 50-year period, and a corresponding shift towards earlier snowmelt. Similar to previous studies in larger Alpine catchments, the decadal variations in mean annual runoff in Alptal's small research catchments reflect the long-term variability in annual precipitation. In the Alptal valley, the most evident hydrological trends were observed in late spring and are related to the substantial change in the duration of the snow cover. Streamflow and water quality are highly variable within and between hydrological events, suggesting rapid shifts in flow pathways and mixing, as well as changing connectivity of runoff-generating areas. This overview illustrates how catchment research in the Alptal has evolved in response to changing societal concerns and emerging scientific questions.  相似文献   

Investigation of inner-basin variation: Impact of large reservoirs on water regimes of downstream water bodies     

Xue Dai  Zhongbo Yu  Guishan Yang  Chong-Yu Xu  Rongrong Wan 《水文研究》2021,35(5):e14241

Large dams and reservoirs alter not only the natural flow regimes of streams and rivers but also their flooding cycles and flood magnitudes. Although the effect of dams and reservoirs has been reported for some vulnerable locations, the understanding of the inner-basin variation with respect to the effects remains limited. In this study, we analyse the Three Gorges Dam (TGD) built on the Changjiang mainstream (Yangtze River) to investigate the dam effect variations in the system of interconnected water bodies located downstream. We investigated the effect of flow alterations along the downstream river network using discharge time series at different gauging stations. The river–lake interactions (referring to the interactions between the Changjiang mainstream and its tributary lakes i.e. the Dongting and Poyang lakes) and their roles in modifying the TGD effect intensity were also investigated in the large-scale river–lake system. The results show that the water storage of the tributary lakes decreased after the activation of the TGD. Severe droughts occurred in the lakes, weakening their ability to recharge the Changjiang mainstream. As a consequence, the effect of the TGD on the Changjiang flow increase during the dry season diminished quickly downstream of the dam, whereas its impact on the flow decrease during the wet season gradually exacerbated along the mainstream, especially at sites located downstream of the lake outlets. Therefore, when assessing dam-induced hydrological changes, special attention should be paid to the changes in the storage of tributary lakes and the associated effects in the mainstream. This is of high importance for managing the water resource trade-offs between different water bodies in dam-affected riverine systems.  相似文献   

水文情势、土壤和水电开发对河流湿地中植物的影响研究进展     

杨娇  厉恩华  夏盈  张莹莹  王学雷 《湿地科学》2020,18(1):115-121

开展环境对河流湿地中植物的影响研究,不仅有助于了解河流湿地中植物与生态环境之间的关系,而且对河流湿地中植物的保护和恢复工作具有重要意义。根据近年来发表的环境对河流湿地中植物的影响研究成果,对河流湿地中植物的范围进行了界定,综述了与河流湿地中植物关系密切的水文情势、土壤和水电开发对其的影响,指出未来对河流湿地中植物的影响研究的方向。  相似文献   

Adjustment of self-formed bankfull channel geometry of meandering rivers: modelling study     

Kensuke Naito  Gary Parker 《地球表面变化过程与地形》2020,45(13):3313-3322

We consider the evolution of the hydraulic geometry of sand-bed meandering rivers. We study the difference between the timescale of longitudinal river profile adjustment and that of channel width and depth adjustment. We also study the effect of hydrological regime alteration on the evolution of bankfull channel geometry. To achieve this, a previously developed model for the spatiotemporal co-evolution of bankfull channel characteristics, including bankfull discharge, bankfull width, bankfull depth and down-channel bed slope, is used. In our modelling framework, flow variability is considered in terms of a specified flow duration curve. Taking advantage of this unique feature, we identify the flow range responsible for long-term bankfull channel change within the specified flow duration curve. That is, the relative importance of extremely high short-duration flows compared to moderately high longer duration flows is examined. The Minnesota River, MN, USA, an actively meandering sand-bed stream, is selected for a case study. The longitudinal profile of the study reach has been in adjustment toward equilibrium since the end of the last glaciation, while its bankfull cross-section is rapidly widening due to hydrological regime change in the last several decades. We use the model to demonstrate that the timescale for longitudinal channel profile adjustment is much greater than the timescale for cross-sectional profile adjustment due to a lateral channel shift. We also show that hydrological regime shift is responsible for the recent rapid widening of the Minnesota River. Our analysis suggests that increases in the 5–25% exceedance flows play a more significant role in recent bankfull channel enlargement of the Minnesota River than increase in either the 0.1% exceedance flow or the 90% exceedance flow. © 2020 John Wiley & Sons, Ltd.  相似文献   

Spatial and temporal patterns of stable water isotopes along the Yangtze River during two drought years          下载免费PDF全文

Huawu Wu  Jing Li  Fan Song  Yanan Zhang  Haixia Zhang  Cicheng Zhang  Bin He 《水文研究》2018,32(1):4-16

Changes in the level of the Yangtze River caused by anthropogenic water regulation have major effects on the hydrological processes and water cycle in surrounding lakes and rivers. In this study, we obtained isotopic evidence of changes in the water cycle of Yangtze River during the two drought years of 2006 and 2013. Isotopic evidence demonstrated that the δ¹⁸O and δD levels in Yangtze River exhibited high spatial heterogeneity from the upper to lower reaches, which were controlled by atmospheric precipitation, tributary/lake water mixing, damming regulation, and water temperature. Both the slope and intercept of Yangtze River evaporative line (δD = 7.88 δ¹⁸O + 7.96) were slightly higher than those of local meteoric water line of Yangtze River catchment (δD = 7.41 δ¹⁸O + 6.01). Most of the river isotopic values were located below the local meteoric water line, thereby implying that the Yangtze River water experienced a certain degree of evaporative enrichment on isotopic compositions of river water. The high fluctuations in the isotopic composition (e.g., deuterium excess [d‐excess]) in the middle to lower reaches during the initial stage of operation for the Three Gorges Dams (2003–2006) were due to heterogeneous isotopic signatures from the upstream water. In contrast to the normal stage (after 2010) characterized by the maximum water level and largest water storage, a relatively small variability in the deuterium excess was found along the middle to lower reaches because of the homogenization of reservoir water with a longer residence time and complete mixing. The effects of water from lakes and tributaries on the isotopic compositions in mainstream water were highlighted because of the high contributions of lakes water (e.g., Dongting Lake and Poyang Lake) efflux to the Yangtze River mainstream, which ranged from 21% to 85% during 2006 and 2013. These findings suggest that the retention and regulation of the Three Gorges Dams has greatly buffered the isotopic variability of the water cycle in the Yangtze catchment, thereby improving our understanding of the complex lake–river interactions along the middle to lower reaches in the future.  相似文献   

Partition-coordinated control of soil and water loss for chestnut forests in the Yanshan Mountain Region,China   总被引：1，自引：0，他引：1  

Xinhui Ding  Guangquan Liu  Xiaoying Liu  Yongsheng Xie  Zhichun Yue 《国际泥沙研究》2019,34(1):58-64

Soil erosion from chestnut forests is one of the most important factors causing land degradation in the Yanshan Mountain Region. A 2-year field study was done to compare the effects on erosion of a control plot (CP), a repaired and maintained horizontal ditch built with an engineering baffle every 6?m (MP 1), and a repaired and maintained horizontal ditch built with an engineering baffle every 8?m (MP 2). The results showed that the slope runoff of chestnut forests was influenced by rainfall characteristic factors. No single rainfall characteristic factor showed dominance for hill slope runoff. The runoff reduction effect of the partition-coordinated erosion control measures (MP 1 and MP 2) was substantial for chestnut forests under high rainfall intensity conditions. However, the runoff reduction efficiency was higher under the conditions of heavy rainfall and low average rainfall intensity than for storms with higher intensity and lower total rainfall. The reduction effect of the partition-coordinated erosion control measures on the runoff and sediment yield of chestnut forest slopes was MP 2 > MP 1 > CP. The runoff reduction rate and erosion reduction rate of MP 2 reached 61.70% and 97.41%, respectively, and that for MP 1 was 54.15% and 85.31%, respectively. Therefore, after a comprehensive comparison, MP 2 was determined to be more effective for soil erosion control for a sloping chestnut forest.  相似文献   

Laboratory investigations of the role of biofilms on stream-bed surfaces in debris-flow runout     

Yong-Jun Tang  Ze-Min Xu  Zhen-Chen Shao  Zhe Ren  Kun Wang  Kui Yang  Jun-Yao Luo  Hai-Yan Gao  Lin Tian 《地球表面变化过程与地形》2020,45(4):999-1012

Debris-flow runout is a fascinating process to understand due to its implications for downstream alluvial fans. Based on the propagation-deposition behaviors of the Dongyuege (DYG) debris flow, in Yunnan, the effect of biofilms on channel surfaces on debris-flow runout is investigated in laboratory flumes with two different internal surfaces: surfaces are lined with granite slabs (Model I) and gravel (Model II), respectively. Our results show that biofilms can significantly reduce frictional resistance to flows. They increase flow velocities, slow down the deceleration of the snouts, prolong runout distances, and subsequently extend the areas covered with resulting deposits, thus greatly assisting the propagation of experimental debris flows. Slippery biofilms consisting mainly of diatoms and their extracellular mucus (ECM) reduce the contact friction between the flume-beds and the overlying fluids, and greatly promote the propagation of tested flows. Well-developed biofilms are found on the underwater channel surfaces of the DYG Creek. Acting as lubricating layers, they likely played a key role in the DYG debris-flow runout. Most of the debris transported during the DYG event was deposited on overbanks, and the sediment that caused the disaster was transported to the populated fan region through the stream-bed clad in the thick biofilms. Owing to their impacts on the development and width of the temporary debris dam breach, the stream-bed covered with biofilms became a direct contributor to the debris-flow hazard. Because of the ubiquitous presence of biofilms on mountain stream-bed surfaces, the development of perennial streamflows can be viewed as an indicator of gully susceptibility to debris flows threatening creek fans. The underwater areas of pre-event channel cross-sections should be regarded as slip or low-friction boundaries, and the parts above stream-levels can be viewed as no-slip boundaries. © 2019 John Wiley & Sons, Ltd.  相似文献   

长江三角洲蓝图重绘的基础科学问题:进展与未来研究     

汪亚平  贾建军  杨阳  周亮  冯威  高建华  魏稳  李占海  史本伟  高抒 《海洋科学》2019,43(10):2-12

在全球气候变化和人类活动影响加剧的背景下,作为河口海岸重要子系统的三角洲正在发生快速变化。长江三角洲地处长江入东海交汇处,是中国最重要的经济核心区之一,对邻近区域乃至整个长江经济带经济社会发展都起着重要作用。由于全球变暖、海面上升和强烈人类活动引发了三角洲系统状态转换,因此以往基于恒定系统状态而获得的有关长江三角洲的认识已不能满足未来需求,迫切需要对未来海面变化、极端事件、流域与河口工程影响下的三角洲物质循环条件、物理过程、地貌冲淤演化、源-汇格局调整等科学问题进行深入研究。在三角洲系统行为、未来演化趋势的预测能力建设中,应重视从海面到海底的综合立体观测系统的发展,以获取关键数据;基于三角洲系统的时、空演化特征,建立三角洲本征态和衍生态的谱系理论。未来需针对系统状态转换而调整原先的经济社会发展模式,以便保护自然资源、重建生态系统,更好地支撑长江经济带发展,重绘长江三角洲发展蓝图。  相似文献   

长江下游区域地温场特征及其能源意义     

朱戈  刘绍文  李香兰  吴迪 《地学前缘》2020,27(1):25-34

区域地热特征及深部温度估算对于油气勘探和地热能资源评价和开发利用具有重要意义,长江下游地区是我国东部经济社会高度发达的地区,其能源需求大,区域热状态研究能为该区地热资源评价提供关键约束。通过整合长江下游地区已有的温度数据和实测岩石物性参数,勾勒出该区的现今地温场特征,并进一步估算其1 000~5 000 m埋深处的地层温度。研究表明,长江下游地区现今地温梯度为16~41 ℃/km,且以18~25 ℃/km居多,苏北盆地区呈现高地温梯度。大地热流值为48~80 mW/m²,其均值为60 mW/m²,表现为中等的地热状态,有利于油气和地热能形成。此外,长江下游地区深部地温估算表明,1 000 m埋深处的温度范围为30~54 ℃,2 000 m时温度范围为50~95 ℃,3 000 m时温度范围为65~130 ℃,4 000 m时温度范围为80~170 ℃,5 000 m时温度范围为100~210 ℃。区域深部地温的展布趋势呈NE向,高温区域集中在安徽南部和江苏东北部。结合60 ℃和120 ℃等温线的埋深分布及区域地质、地球化学和地热特征,初步探讨了该区油气与地热资源的有利区带及其相应的开发利用类型。  相似文献   

Confronting the nitrogen challenge: Options for governance and target setting     

《Global Environmental Change》2019

The release of excessive anthropogenic nitrogen contributes to global climate change, biodiversity loss, and the degradation of ecosystem services. Despite being an urgent global problem, the excess nitrogen is not governed globally. This paper considers possible governance options for dealing with excessive nitrogen through target setting, which is an approach commonly adopted to address global environmental problems. The articulation of the nitrogen problem and the numerous international institutions dealing with it, provide evidence of a nitrogen regime characterised by limited coordination and targets covering sources and impacts only partially. This calls for improving the nitrogen governance in the direction of more integrated approaches at the global scale. In this vein, the paper investigates two opposite governance options – here labelled as ‘holistic’ and ‘origin-based’ – and evaluates them for their capability to define solutions and targets for human-induced nitrogen. From the analysis, it emerges that origin-based solutions can be preferable to holistic solutions as they can be more specific and potentially have greater immediate results. Independent from which governance arrangement is chosen, what matters most is the speed at which an arrangement can deploy solutions to combat (fast-growing) nitrogen pollution.  相似文献