We examine the multiscale influence of environmental and hydrological features of the riverine landscape on spatial and temporal variation in fish assemblages in eastern Australia. Multiresponse artificial neural network models provided accurate predictions of fish assemblages in the Mary River based on species presence–absence data (mean Bray–Curtis similarity between predicted and observed composition = 84%) but were less accurate when based on species relative abundance or biomass (mean similarity = 62% and 59%, respectively). Landscape- and local-scale habitat variables (e.g., catchment area and riparian canopy cover) and characteristics of the long-term flow regime (e.g., variability and predictability of flows) were more important predictors of fish assemblages than variables describing the short-term history of hydrological events. The relative importance of these variables was broadly similar for predicting species occurrence, relative abundance, or biomass. The transferability of the Mary River predictive models to the nearby Albert River was high for species presence–absence (i.e., closer match between predicted and observed data) compared with species abundances or biomass. This suggests that the same landscape-scale features are important determinants of distribution of individual species in both rivers but that interactions between landscape, hydrology, and local habitat features that collectively determine abundance and biomass may differ.

Flow regulation by large dams has transformed the freshwater and floodplain ecosystems of the Middle Amur River basin in Northeast Asia, and negatively impacted the biodiversity and fisheries. This study aimed to develop environmental flow recommendations for the Zeya and Bureya rivers based on past flow rate records. The recommended floodplain inundation by environmental flow releases from the Zeya reservoir are currently impracticable due to technical reasons. Therefore, the importance of preserving the free-flowing tributaries of the Zeya River increases. Future technical improvements for implementing environmental flow releases at the Zeya dam would improve dam management regulation during large floods. The recommendations developed for environmental flow releases from reservoirs on the Bureya River should help to preserve the important Ramsar wetlands which provide habitats for endangered bird species while avoiding flooding of settlements. The results emphasize the importance of considering environmental flow during the early stages of dam planning and the need to enhance the role of environmental flow in water management planning.

三峡水库蓄水后,长江中下游物理生境发生明显变化,一定程度上影响河流功能的发挥。采用资料分析和文献综述,研究了三峡水库蓄水运用后长江中下游水文条件、河道形态、植被等典型物理生境的变化,总结了其对防洪、航道条件、供水、典型水生生物的影响。提出了应加强研究内容:①监测方面,包括长江中下游系统性和长期性监测、河(航)道治理工程、生态调度试验效果监测等。②规律和机理方面,包括河道形态变化机制和共性规律、干流洲滩植被变化机制、长江中下游洪水位和底栖动物对物理生境变化的响应规律和阈值等。③方法和对策方面,包括多因素影响下长江中下游水文条件中长期变化趋势预测方法,适应物理生境变化并满足需求的整治技术,满足供水、底栖、鱼类繁殖等目标的水库优化调度方案等,物理生境变化-影响效应-改善策略和技术全过程一体化研究。研究成果可为长江大保护及其健康发展提供参考。

Hydrologic regimes play a major role in determining the biotic composition, structure, and function of aquatic, wetland, and riparian ecosystems. But human land and water uses are substantially altering hydrologic regimes around the world. Improved quantitative evaluations of human‐induced hydrologic changes are needed to advance research on the biotic implications of hydrologic alteration and to support ecosystem management and restoration plans. We propose a method for assessing the degree of hydrologic alteration attributable to human influence within an ecosystem. This method, referred to as the “Indicators of Hydrologic Alteration,” is based upon an analysis of hydrologic data available either from existing measurement points within an ecosystem (such as at stream gauges or wells) or model‐generated data. We use 32 parameters, organized into five groups, to statistically characterize hydrologic variation within each year. These 32 parameters provide information on ecologically significant features of surface and ground water regimes influencing aquatic, wetland, and riparian ecosystems. We then assess the hydrologic perturbations associated with activities such as dam operations, flow diversion, groundwater pumping, or intensive land‐use conversion by comparing measures of central tendency and dispersion for each parameter between user‐defined “pre‐impact” and “post‐impact” time frames, generating 64 Indicators of Hydrologic Alteration. This method is intended for use with other ecosystem metrics in inventories of ecosystem integrity, in planning ecosystem management activities, and in setting and measuring progress toward conservation or restoration goals.

近年来青藏高原暖湿化加剧了江河源区产汇流和侵蚀输沙过程的变化，而冰冻圈要素的变化使得该过程更加复杂。采用突变检验与IHA-RVA分析了沱沱河1986—2017年径流量和输沙量的变化程度，并基于PLS-PM结合其他环境因子对水沙通量的变化进行归因分析，结果表明：①沱沱河水沙通量于1998年突变后显著增加，整体改变度分别为71.2%和67.5%，为高度改变，表明气候变化对河源区水沙通量的影响不亚于人类活动对中下游的影响。②在气温与降水的驱动下，5~10月水沙通量显著增加，各月变化程度受到土壤、河道冻结程度以及植被变化的影响；年输沙量的变化由极端输沙事件的增加主导，降水量、冰川融水量和土壤解冻程度是主要影响因素。③寒区水沙过程受降水、冰川、土壤冻融及植被的综合影响，有待对其进一步研究以保障青藏高原生态屏障建设与周边区域的可持续发展。

In recent decades, the warming and humidification of the Tibetan Plateau have aggravated changes in the runoff and sediment transport processes in the headwater area, and the uniqueness of the cryosphere has made them more complex. In this study, abruption tests and IHA-RVA were performed to assess the variation in the runoff and sediment flux of the Tuotuo River before and after the abrupt change from 1986 to 2017. PLS-PM attribution analysis was performed using environmental factors for runoff and sediment flux change attribution. The following three important conclusions were drawn: first, from 1986 to 2017, the runoff and sediment flux of the Tuotuo River changed abruptly around 1998, and the overall degrees of change were 71.2% and 67.5%, respectively; both were highly altered. This indicates that the impact of climate change on runoff and sediment flux in the headwater was not smaller than that of human activity downstream. Second, under the influence of temperature and precipitation, runoff and sediment fluxes from May to October increased significantly, and the degree of abruption was affected by the thawing degree of the soil, river channel, and vegetation coverage. The variation in the sediment flux was dominated by extreme sediment transport events, which were primarily caused by increased rainfall, ice melting, and soil thawing. Third, the runoff and sediment processes in cold regions are complex because of the combined influence of rainfall, glaciers, soil freeze-thaw, and vegetation. Therefore, it is necessary to further study the local region's ecological security and sustainable development downstream.

水库运行改变了坝下游水沙输移条件,在河道冲刷的同时,引起水位过程出现适应性调整。本文以长江中游荆江河段为对象,采用多项式拟合法,对比分析1991—2016年间分级流量—水位变化特征,采用基于河流动力学原理的分离变量法,识别河道冲淤、下游控制水位及河床综合糙率等变化对分级流量—水位变化的影响程度。研究表明：1991—2016年间,长江中游荆江河段同流量—枯水位呈下降趋势,2009年以来降幅增大;河道冲刷是引起同流量—枯水位下降的主控因素,河床综合糙率增加抑制了同流量—枯水位下降起到积极作用。1991—2016年间,荆江河段同流量—洪水位经历了先减小后增大的“凹”线型变化,2003年以前洪水特征为“高洪水流量—高水位”,2009年以来逐渐演化为“中大洪水流量—高水位”,同流量—洪水位特性发生转变;河床综合糙率增大是同流量—洪水位抬升的主控因素,河道冲刷抑制了同流量—洪水位的抬升态势。在航道条件及防洪情势上,应重点防控近坝段沙质河段冲刷引起的水位下降溯源传递作用,其洪水流量—水位特性的转变,不利于减缓荆江河段的防洪压力。

Water and sediment transport processes have been changed by the operation of larger scale reservoirs, which can result in the adjustments of river topography and water levels. The polynomial fitting method was applied to analyze the variation characteristics of the water levels under different characteristic water discharges in the Jingjiang reach of the Yangtze River during 1991-2016. The segregation variable method was used to estimate the contributions of the varied riverbed evaluation, the downstream controlled water level and the comprehensive roughness on the altered water level at the same flow. The results obtained are as follows: (1)The low water level in the Jingjiang reach of the Yangtze River during 1991-2016 presented a significant downward trend, and this trend intensified since 2009; riverbed scouring was the dominant factor for the reduced low water level, while the increased roughness alleviated this reduction. (2) During 1991-2016, the high water level decreased firstly and then increased. The variation characteristic of "high flood discharge with high water level" before 2003 transformed into "average flood discharge with high water level" since 2009. The increased comprehensive roughness was the main reason for the increased high water level, while the river scouring alleviated this increase. For navigation conditions and flood control, the intensifying riverbed scouring of the sandy reaches downstream dams enhanced the effects of the downstream water level on the upstream water level. (3) This led to the insufficient water depth in the reaches below dams, which should arouse great attention. The variation characteristics of high water level increased the flood pressure in the middle reaches of the Yangtze River.

目前对三峡水库蓄水后荆江河段的洲滩演变还缺乏完整认识。基于三峡水库蓄水前后枯水期遥感影像,分析了荆江洲滩的冲淤变化与分布及形态演变。结果表明,蓄水后荆江洲滩总面积持续冲刷减小,累计冲刷4.56 km²,大部分发生在蓄水后前6年（冲刷速率0.55 km²/a）。上、下荆江洲滩的冲淤演变存在差异性。上荆江洲滩总面积一直处于冲刷萎缩中,且其强度明显大于下荆江,累计冲刷6.46 km²;下荆江前期（2002-2009年）冲刷、后期（2009-2015年）淤增,累计淤1.90 km²。在冲淤分布上,上荆江凸岸滩持续冲刷萎缩,凹岸滩前期冲刷、后期略有淤增,心滩（洲）前期淤积增长而后期冲刷萎缩;下荆江主要是凸岸滩冲刷,凹岸滩和心滩（洲）有所发展。根据滩体位置活动和冲淤动态性,荆江心滩（洲）演变被划分为8种典型类型。在形态演变上,上荆江以凸岸突出滩体和边滩发育的凹岸滩冲刷显著,形态变化不大。下荆江凸岸滩上游弯侧冲蚀后退、湾顶退缩、下游弯侧淤积伸长,形态趋向低弯扁平化,在高弯曲特定河湾平面形态格局下凸岸冲刷—淤积过程延伸到相邻河湾凹岸,成为下荆江凹岸滩和心滩淤积发展的重要因素,但淤积一般不越过凹岸湾顶。

At present, there is a lack of sufficient understanding of the evolution of floodplains and bars (FB) at the Jingjiang reach of Yangtze River after Three Gorges Reservoir impoundment. The erosion/accretion pattern and morphological evolution of FB at the Jingjiang reach were studied using remote sensing images acquired in low water periods before and after Gorges Reservoir impoundment. The results showed that the total area of FB at the Jingjiang reach shrank continually after the reservoir impoundment. By 2015 an area of 4.56 km² had been scoured away, and most of the scour occurred within the first 6 years after the impoundment at an erosion rate of 0.55 km²/a. There were evident differences in erosion/accretion pattern and in morphological evolution between the upper and lower sections of Jingjiang reach. The total area of FB at the upper Jingjiang has continually decreased due to scouring after the impoundment, and the scouring intensity was greater than that in the lower Jingjiang. In contrast, erosion of the lower Jingjiang took place in the early period after the impoundment (2002-2009), but accretion was observed in the later period (2009-2015). In erosion/accretion distribution, the floodplains of upper Jingjiang reach were continually scoured and shrunk while the bars at concave banks were scoured in the early period but were accreted slightly in the later period; the mid-channel bars of upper Jingjiang were accreted in the early period but were scoured in the later period. In contrast, erosion mainly occurred at the floodplains of lower Jingjiang, while the bars at its concave banks and mid-channel bars were accreted. The mid-channel bar evolution at the Jingjiang reach after the reservoir impoundment was classified into eight types according to their position movement and erosion/accretion dynamics. On morphological evolution, the protruding parts of floodplains and the bars at concave banks of the upper Jingjiang were visibly eroded, while the morphology changed little. At the lower Jingjiang, however, the floodplains evolution had a characteristic pattern that the upstream part was eroded back, with a shrinkage of the top, while the downstream part was accreted, resulting in the alteration of convex bank from a highly curved morphology to a flattening-curved morphology. This erosion-accretion process of floodplains at the upstream convex bank even extended to the adjacent downstream concave bank when there was no obvious straight section connecting the neighboring highly curved bends or when the upstream convex bank shared the same bank with the downstream concave bank. Extension of upstream floodplain accretion to the downstream concave bank was an important reason for the development of both the bars at concave banks and the mid-channel bars at the lower Jingjiang. Generally, the accretion at the concave bank did not span to the top of concave bank.

大型水库的兴建深刻改变了下游水沙输移特点,进而导致河床演变规律显著调整,水库下游弯曲河型对水沙过程改变响应敏感,是水库下游河床演变、航道整治、河势控制等方面研究的关键区域。本文基于1996-2016年的实测水文、地形资料,对长江三峡水库下游弯曲河型的演变规律及其驱动机制开展研究,结果表明：① 三峡水库蓄水前,下荆江存在“凸淤凹冲”、“凸冲凹淤”两类弯曲河型,而三峡水库蓄水后均表现为“凸冲凹淤”的一致性规律;② 在水库拦沙作用的影响下,下荆江河段平滩河槽存在累积性冲刷现象,冲刷部位集中于枯水河槽与基本河槽之间的低滩,冲淤部位调整主要由变化的流量过程所驱动,上游河势、河道边界以及支流入汇等因素均有一定驱动作用;③ 在三峡水库蓄水后缺乏大洪水的情况下,凸岸水流挟沙力随流量增加逐渐增强,水流对凸岸冲蚀力度在平滩流量级附近（20000~25000 m3/s）达到最强,平滩流量附近流量级的持续时间超过20天时,弯曲河道发生凸冲凹淤现象。而悬沙中造床粗沙的减少,增强了水流冲刷强度,加剧了凸岸的冲蚀程度。

The impoundment of huge reservoirs deeply changes the water and sediment process in the downstream reaches and then influences the evolution of the downstream rivers. The meandering rivers sensitively responded to the variation of water and sediment process. That is why the meandering rivers are the important survey regions of river evolution, channels regulation and flood control projects. Based on the measured hydrological and morphological data from 1996 to 2016, the evolution law and its driving mechanism of the typical meandering river in the downstream reaches of Three Gorges Reservoir (TGR) are studied. By building the relationship between the cross-sections variation and the influencing factors, the mechanism is well examined. The results show that (1) before the establishment of the Three Gorges Reservoir, the meandering rivers have two types of evolution laws named "Convex banks deposition and concave banks erosion" and "Convex banks erosion and concave banks deposition". After the impoundment of the great project, the meandering rivers are featured only by the latter type. (2) After the retaining of water and sediment of TGR since 2003, the low flow channel and bankfull channel in Lower Jingjiang River have been continually eroded and the erosed areas are found in the low shoal of convex banks. The phenomenon is mainly resulted from the variation of water flow and sediment transportation and also influenced by the upstream river region, riverbed boundaries and branches. (3) The growing process of flow discharge from low water to bankfull discharge can lead to the increase of sediment transport capacity. When no big flood of discharge over 35000 m3/s is observed after the impoundment of TGR, the duration of bankfull discharge (22000-25000 m3/s) decides the erosion or deposition of convex banks after the impoundment. When the number of lasting days of bankfull discharge (22000-25000 m3/s) exceeds 20, the convex banks will be eroded. The concentration of coarse sand decrease contributes to the improvement of strength of water.

利用1951—2018年中国699个气象站逐日的气温、降水数据，采用Mann-Kendall检验、小波分析、RClimDex极端气温指数方法，研究中国气温和降水时空演变特征。结果表明：在时间上，中国气温呈现明显的增加趋势，降水增加滞后且缓慢，气温和降水存在多周期变化特征，在大时间尺度上存在关联关系，以最高气温表达的冰冻日数ID0和暖昼日数TX90p较之以最低气温表达的霜冻日数FD0和暖夜日数TN90p变化幅度小，最长持续湿润日数和最长持续干旱日数呈下降趋势，气候变化以暖湿化为主要特征；在空间上，平均气温和降水量都表现出纬度方向上的降低趋势，等值线整体向北移动，很大程度上受地形影响，表现出相辅相成的空间分布特征，暖昼日数TX90p和夏季日数SU25在全国范围内均为正值，冰冻日数ID0和霜冻日数FD0存在大部分区域的减小，最长持续干旱日数与最长持续湿润日数在空间上的变化存在一定程度的相反趋势，极端降水事件存在增加趋势。研究气温和降水的时空演变特征是了解和应对气候变化对区域影响的重要内容。

This study used daily temperature and precipitation data from 699 weather stations in China from 1951 to 2018 to study the spatiotemporal evolution characteristics of temperature and precipitation in China， by using Mann-Kendall test， wavelet analysis， and RClimDex extreme temperature index methods. The results show that： In terms of time， the temperature in China presents an obvious increasing trend； the increase in precipitation is lagging and slow； the temperature and precipitation have multi-period changes； and there is a correlation on a large time scale. With the number of freezing days ID0 expressed by the highest temperature and abnormal warmth compared with the number of frost days FD0 and the number of warm night days TN90p expressed in the lowest temperature， the number of continuous days TX90p has a smaller change. The longest continuous precipitation days CWD and the longest drought duration CDD show a downward trend. Climate change is mainly characterized by warming and humidification. Spatially， the average temperature and precipitation both show a decreasing trend in the latitude direction. The contours move northward as a whole， which is largely affected by the topography， showing complementary spatial distribution characteristics. The number of warm days TX90p and the number of summer days SU25 are positive across the country. The number of freezing days ID0 and the number of frost days FD0 decrease in most areas. The longest continuous dry days CDD and the longest continuous humid days CWD have a certain degree of opposite spatial variation， and there is an increasing trend in extreme precipitation events. Studying the temporal and spatial evolution characteristics of temperature and precipitation is an important part of understanding and coping with the impact of climate change on the region.