Trends and prospects in the Yangtze River Basin research: A bibliometric analysis

The management and protection of the world's major river basins have received increasing attention, and a series of related measures, including fishing bans and ecological engineering restoration, has been pioneered in the Yangtze River Basin (YRB). This paper provides a quantitative and qualitative analysis of research trends and hotspots in the water environment of the YRB through bibliometric means. The database period was from its inception to December 31, 2020. This review combines the changing trends in the water environment of the YRB in the form of keywords. The results show that the governance of the YRB is based on the relationship between “water” and “sediment” as an entry point, focusing on changes in the “temporal” and “spatial” allocation of water resources; further, when considering the problem of “eutrophication” caused by the release of “nitrogen” and “phosphorus” from “sediments,” water quality factors such as “heavy metal pollution” and “organic pollution” are becoming more prominent; then water quality factor affects “biodiversity,” aquatic ecology becomes more and more concerned, and “ecological risk” factor is taken into consideration. Therefore, future management of the YRB requires consideration of all elements of the basin, including water resources, water quality, and aquatic ecology, and how to coordinate these all material elements is the obstacle and breakthrough point. In addition, further studies on research frontiers have revealed that ecological risk, emerging bioinformatics technologies, and, source apportionment will become the new and popular directions and trends in research. This review is intended to provide insights into the management of other large river basins around the world.     

基于GIS的黄河内蒙古段冰下河床三维可视化方法与应用

为了揭示冰封期黄河河床的演变过程,基于地理信息系统(GIS)技术,研究了黄河内蒙古段冰下河床三维可视化分析方法。根据野外测量结果进行了河道地形剖析,绘制了河床地形等值线图、矢量地形图及弯道典型断面;在可视化过程中,绘制了冰封期和畅流期河床的三维表面图及地貌晕渲图,并对冰封期和畅流期河床冲淤变迁做了定量计算,对冰盖流和明渠流两种条件下的河床空间进行了对比分析。结果表明:运用GIS技术可以实现河床表面的三维建模和不同时期河床冲淤变化的定量计算,及时反映出河道变迁过程,准确计算河床冲淤量,阐释冰封期泥沙与水流运动相互作用的机理。     

Complexity and trends analysis of hydrometeorological time series for a river streamflow: A case study of Songhua River Basin,China

In China's national economic growth, an important role is being played by the Songhua River because of the river's abundant resources and natural conditions. Therefore, study of hydrometeorological time series is very important to understand the basin behaviour. This research uses the snow cover data derived from MODIS, streamflow, and meteorological records in the Songhua River Basin to evaluate similarity, complexity, and trends in the snow cover, temperature, precipitation, and streamflow. In this paper, we suggest a new method of ranking the statistics symbolic sequences to examine the degree of similarity (distance measurement) between meteorological stations and compare it with non‐parametric correlation methods and also investigate the deviations in the complexity of a hydrometeorological time series. Information‐based similarity index and multiscale entropy confirm that the hydrometeorological time series of different stations have self‐similarity and abundant complexity. Wavelet entropy is also used to investigate the basin behaviour by taking streamflow records and population. It is found that with the increase in population and urbanization, the complexity values are increased. The results also exhibit that due to increase in urbanization, it affects the hydrological process and nature of environment resulting in complex catchment behaviour. Furthermore, the streamflow trend results displayed significant decline (22.21 m³/s × year^?1) in the Songhua River. The results also indicated that the seasonal snow cover trend has no impact on changes of the streamflow. However, the decline of the streamflow may be influenced by the significant human activity upstream of the Songhua River.     

A Comparison of Metabolic Rates in Off‐Channel Habitats of the Middle Mississippi River

Autochthonous material has been found to be an important base in large river food webs. However, a spatial understanding of primary production in large rivers is lacking. We modeled primary productivity and community respiration (CR) during a low water period in two types of off‐channel habitat present in the Middle Mississippi River, side channels and wing dike fields. Wing dike fields are constantly connected to the main channel and are well mixed along most of their length, while side channels are typically connected only at the top and mouth. Gross primary production (GPP) in wing dike fields ranged from 0.0 to 8.9 g O₂ m^?2 D^?1 and in side channels GPP ranged from 0.4 to 33.5 g O₂ m^?2 D^?1. Both habitat types experienced periods of positive net ecosystem production (NEP) especially in the late summer and early fall. Correlations between metabolic rates and ecosystem characteristics differed between habitat types. Discharge was negatively correlated to NEP in wing dike fields but was not associated with metabolic rates in side channels. Light was positively correlated with GPP and CR at both site types and with NEP in side channels. These areas are protected from high velocity and likely experience greater light penetration, allowing more photosynthesis to take place especially during low water periods. This study demonstrates the potential for high productivity in off‐channel habitats that are permanently connected to the main channel. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of pool formation and flash flooding on relative abundance of young‐of‐year flannelmouth suckers in the Paria River,Arizona

Flannelmouth sucker, Catostomus latipinnis, a fish endemic to the Colorado River basin in the western United States, appears to experience poor recruitment to adult size in the Colorado River, downstream of Glen Canyon Dam. Lack or impermanence of rearing areas for young‐of‐year (YOY) fish is hypothesized to be the problem. Knowing the importance of tributary mouths as rearing areas in other river systems, we studied use of the mouth of the Paria River, a tributary of the Colorado River, by YOY flannelmouth suckers, and the availability of rearing area in the mouth at different flow levels in the Colorado River in 1996 and 1997. We also examined the relationship between flash floods in the Paria River and catch‐per‐unit‐effort (CPUE) of YOY in the Paria River between 1991 and 1996. Maximum mean daily discharge in the Paria River was inversely correlated with CPUE of YOY flannelmouth suckers (Spearman Rho=?0.9856, p=0.0003) during their critical rearing period (15 March–30 June). Thus, it appears that YOY flannelmouth suckers rear longer in the Paria River in years when flash flooding is minimal. Recruitment of YOY flannelmouth suckers at the Paria River may also be improved by enhancing pool formation during spring and summer rearing seasons. YOY flannelmouth sucker was captured in a pool created by high Colorado River flows (≥336 m³/s) that inundated the mouth of the Paria River during spring and summer, 1996. In 1997, high flows (about 550–750 m³/s) in the Colorado River during winter and spring initially inundated the Paria River and formed a pool in the mouth. However, these high flows eventually caused 0.5–1.0 m of suspended sediment from the incoming Paria River to deposit in the mouth. Thus, despite higher flows than 1996, the slackwater area formed only occasionally in 1997. Differences in pool formation between 1996 and 1997 demonstrate that pool formation cannot be inferred solely from Colorado River flows. Copyright © 2001 John Wiley & Sons, Ltd.     

River regulation in Southern China: Ecological implications,conservation and environmental management

Southern China—i.e. China south of the Chang Jiang (Yangtze River)—has a monsoon climate with pronounced wet and dry seasons and consequent effects on river discharge. There is considerable inter-year variation in the duration and intensity of the monsoon, and the region experiences frequent floods and droughts which cause considerable human misery. The importance of floods as an incentive for river regulation is apparent from the fact that 10% of China's area, inhabited by 65% of the population and responsible for 70% of the agricultural and industrial output, is below the flood level of major rivers. Irrigation and hydroelectric power are additional benefits to be derived from river regulation. China has a 4000 year history of river regulation, but most of the changes that have been made to riverine environments have not taken account of the ecological consequences. This review considers the ecological implications of planned or existing schemes for the regulation of southern Chinese rivers. Particular attention is paid to the Chang Jiang and Zhujiang (Pearl River) which, by volume of discharge, are the two largest rivers in China. Large-scale water-transfer projects and the planned construction of the biggest dam in the world (the Three Gorges High Dam) on the Chang Jiang have the potential to affect fisheries stocks and endangered fish species, to alter inundation patterns in wetlands of international conservation significance and may contribute to the extinction of the endemic and highly endangered Chinese alligator (Alligator sinensis) and Chinese river dolphin (Lipotes vexillifer). In addition, deforestation and soil erosion in the Chang Jiang basin have given rise to siltation and degradation of floodplain habitats. In the Zhujiang, dam construction has caused reductions in fisheries stocks but here, as elsewhere in China, the ecologically damaging consequences of river regulation are exacerbated by overfishing and increasing pollution of rivers by sewage, pesticides and industrial wastes.     

Effects of land‐use change and climate variability on streamflow in the Woken River basin in Northeast China

In this study, the soil and water assessment tool, which is a widely used hydrological model, is applied to study the response of streamflow to land‐use changes and climate variability in the Woken River basin in northeastern China. This model is calibrated and verified based on sensitivity analysis to simulate the effects of land‐use change, climate variability, and extreme land‐use scenarios on streamflow. Simulations are performed to construct different scenarios for quantitative analysis. Compared with the base period, the land‐use change reduced the annual average streamflow and had little effect on the monthly streamflow. Climate variability increased the average annual streamflow and had a substantial effect on monthly streamflow. The effect of climate variability on streamflow was much greater than that of land‐use changes. Under the extreme land‐use scenarios, the annual average streamflow under the forestland scenario decreased, and the average annual streamflow under the grassland and agricultural land scenarios increased. Both the forestland and grassland scenarios exhibited lower monthly streamflow from March to August with especially large influences in June–August, which was when floods were more likely to occur. The agricultural land scenario exhibited the opposite trend. These results indicate that climate variability will obviously change streamflow and that natural disasters related to both high and heavy precipitation must be emphasised. Relevant departments can optimize the land‐use structure and spatial layout to mitigate the negative effects of climate variability.     

Spatial patterns of fish communities in the Upper Mississippi River System: assessing fragmentation by low‐head dams

We assessed the similarity of fish communities among river reaches to assess community‐level fragmentation by low‐head dams in the Upper Mississippi River System (UMRS). The spatial coverage of standardized electrofishing sampling used in the Long Term Resource Monitoring Program (LTRMP) was extended for three of the six regional trend areas (RTA; pools 4, 13, and the Open River Reach) to include river reaches (outpools) immediately upstream and downstream from the standard RTA from 15 June to 31 October 2000. Additionally, pools 19 and 20 were sampled in September 2000. Cluster analysis and non‐metric multidimensional scaling of community composition and structure data revealed two major groups, upper and lower reaches, and four (for composition) or five (for structure) sub‐groupings of river reaches. In general, all outpools grouped with the nearest RTA for both community composition (no exception) and community structure (one exception). This suggests that fragmentation of fish communities from low‐head dams is minimal. Mantel correlations demonstrated strong inverse association between the similarity of fish communities with the distance between reaches. Habitat variables measured during electrofishing collections were significantly correlated with spatial variation of fish composition and community structure, but provided only marginal improvements to correlations with distance between reaches alone. Furthermore, habitat variability among river reaches also was related to distance between reaches. Determining the extent to which variation of fish communities is related to habitat or demographic processes (e.g. migration, larval drift, source‐sink dynamics) will be challenging for this system. Although low‐head dams on the UMRS may restrict movements for individuals and populations of certain fish species, we found little evidence that these effects have led to substantial, community‐level fragmentation. Copyright © 2006 John Wiley & Sons, Ltd.     

Variations in fish assemblages in a tributary of the upper Paraná River,Brazil: A comparison between pre and post‐closure phases of dams

This paper purposed to evaluate alterations in fish assemblage (structure and species richness) and variations in the abundance of the most abundant species captured in the Piquiri River, due to the closure of Porto Primavera (in 1998; located upstream the Piquiri River mouth) and the Itaipu (in 1982; located downstream) dams in the upper Paraná River. The effects of selected environmental variables were also determined. Fishes were sampled during four distinct periods. Six samplings were conducted in each period, at two different sites (Campina and Apertado). For sampling, gill and trammel nets were used. Species abundances were indexed by catch per unit of effort. Spatial and temporal changes in environmental variables were summarized by a principal components analysis (PCA). To summarize structure of the assemblage, a nonmetric multidimensional scaling (NMS) was used. To test the significance of between‐group differences at each periods and sites we used a multiresponse permutation procedure (MRPP). To test the association between fish assemblage and the environmental variables matrices, we used procrustean superimposition approach. A total of 2693 individuals were caught, belonging to 69 species, 4 orders and 19 families. Species richness differed spatially; the Campina site had greater mean richness (13) per sampling than the Apertado site (10). The structure of the fish assemblages showed significant temporal and spatial variations, which were more evident in the last period at the Apertado site (after the closure of Porto Primavera Dam). Spatial and temporal changes in structure of fish assemblages were not associated to environmental variables. Temporal changes in abundance, both in number and in weight, of the most abundant species were verified in both sites. The lack of migratory species was highlighted, which sharply decreased in the last studied period, when they were replaced by sedentary species. These findings appear to be related to regional factors, such as the decrease of floods registered in the upper Paraná basin, exacerbated by the control prompted by dams. Copyright © 2009 John Wiley & Sons, Ltd.     

Long‐term data assessment of chironomid taxa structure and function in the River Thames

Discharge of the River Thames is already regulated to prevent flooding and to satisfy demands for water. A flood alleviation channel is under construction, while a pumped‐storage reservoir has been proposed to further regulate discharge for water supply. The aim of this investigation was to assess the suitability of available quantitative macroinvertebrate data for detecting significant change in biological structure and functioning, and substratum composition, following the implementation of these schemes. Pupal exuviae of Chironomidae (non‐biting midges) were collected from eight surveys of the freshwater River Thames from 1977 until 1997. Multivariate and univariate statistics were used to investigate biological variation between surveys, independently of variation between sites. Over 48% of biological variation was explained by the available physical and chemical data. Temporal variation was almost independent of spatial variation. River discharge was the most important environmental variable correlated with chironomid taxa abundances between surveys, particularly in the lower Thames. High concentrations of un‐ionized ammonia occurred during 1977, the effects of this were also greatest in the lower Thames. Indicator taxa have been identified which can be used as a simple monitoring tool to track the effects of varying flow and nitrogen flux between surveys. Proportions of fine sediment‐dwelling chironomids, and their functional feeding types, have not significantly changed at sampling points immediately above or below the proposed reservoir or the imminent confluence with the flood alleviation channel over the 20‐year survey period. These data provide the basis for detecting significant impacts by such schemes if or when they are completed. This knowledge would benefit any future plans to regulate or alleviate river flows. Copyright © 2000 John Wiley & Sons, Ltd.     

Change‐point alterations of extreme water levels and underlying causes in the Pearl River Delta,China

In this paper, the Bayesian model and Lepage test were used to detect change point and to analyse associated statistical properties of high/low water levels in summer (June, July and August (JJA)) and winter (December, January and February (DJF)) months across the PRD (Pearl River Delta). The results indicate that: (1) two time intervals, that is 1979–1981 and 1988–1995, witness abrupt changes of SmH/SmL (summer mean high water level/summer mean low water level). The lower PRD is dominated by increased mean and coefficient of variation (Cv) of SmH. Increased mean but decreased Cv of SmL can be observed in the Mainstem Pearl River; (2) WmL (winter mean low water level) and WmH (winter mean high water level) of about 74% of the total stations have two change points occurred roughly during 1969–1971 and 1993–1995. First change points of WmH are mainly characterized by increased mean and Cv, but decreased mean and increased Cv of WmL can be observed across major parts of the PRD. The driving factors causing abrupt changes of water levels are various. Intensive human activities cannot be ignored, for example in‐channel dredging and reallocation of the streamflow within the river channels due to human‐induced topographical changes of river channel. Different responses of high/low water levels to externally influencing factors and interactions between influencing factors make the alterations of the water levels across the PRD more complicated. The findings of this paper will be helpful for the management of the PRD and human mitigation to natural hazards under the changing environment. Copyright © 2008 John Wiley & Sons, Ltd.     

Long‐term Hydrologic Variability in a Large Subtropical Floodplain River: Effects on Commercial Fisheries

We analysed the effects of decadal and annual hydrologic fluctuations on freshwater fisheries catches in the Middle Paraná River for a period of six decades from the 1930s to the 1980s. The climatic fluctuations in this period strongly affected the hydrology of the Middle Paraná River and the characteristics of its flow regime. The magnitude of floods as well as maximum, minimum and mean water levels increased progressively from 1930s until the 1980s concomitantly with increasing frequency and intensity of El Niño Southern Oscillation events that resulted in differentiation of distinct hydrological periods. The flood pulses were significantly more frequent and of greater magnitudes during the 1970s and 1980s. These large floods resulted in increased commercial fish catches in the 1980s, possibly because of enhanced recruitment. Specifically, large floods increased the commercial fish catches 2 years later. This effect was stronger for species that use floodplain habitats as areas of reproduction and larval nurseries, such as Prochilodus lineatus. We conclude that the natural flow regime of the Paraná River and perhaps other large subtropical rivers must be preserved in order to sustain their productive fisheries. Copyright © 2016 John Wiley & Sons, Ltd.     

A dynamic corridor‐searching algorithm to seek time‐varying instream flow releases for optimal weir operation: comparing three indices of overall hydrologic alteration

A full range of natural flow regime has been widely recognized as a primary driving force for sustaining the integrity of a riverine ecosystem. Existing instream flow methods strive to assure a constant minimum flow but not the natural flow variability. We present in this paper a dynamic corridor‐searching algorithm to seek the optimal time‐varying scheme for instream flow releases. A compromise programming (CP) is employed to search the optimal solution of an objective function aggregating the ecosystem and human needs objectives. The ecosystem need objective is represented by an overall index of hydrologic alteration, which integrates 32 indicators of hydrologic alteration (IHA) derived from the range of variability approach (RVA). The human need objectives are expressed by shortage ratios for the agricultural and municipal water supplies. The proposed method is applied to a weir operation in Taiwan. Three approaches to evaluating the overall degree of hydrologic alteration (i.e., the three‐class, fuzzy‐based, and overall‐mean approaches) are compared here. The results show that the time‐varying schemes improve the human need objective, but only slightly deteriorate the ecosystem need objective. Such advantages increase with the time‐varying frequency. For the wet periods, smaller flow releases may be prescribed; for the dry periods, however, greater releases must be specified to secure a lower degree of overall hydrologic alteration. It is also revealed that use of the three‐class approach to evaluate the overall hydrologic alteration facilitates to eliminate highly altered IHA and maintain those low‐flow characteristics subtle to flow diversions. However, such outcomes are achieved at the cost of greater deficits for human water demands. Copyright © 2007 John Wiley & Sons, Ltd.     

Population Trends,Bend Use Relative to Available Habitat and Within‐River‐Bend Habitat Use of Eight Indicator Species of Missouri and Lower Kansas River Benthic Fishes: 15 Years After Baseline Assessment

A baseline assessment of the Missouri River fish community and species‐specific habitat use patterns conducted from 1996 to 1998 provided the first comprehensive analysis of Missouri River benthic fish population trends and habitat use in the Missouri and Lower Yellowstone rivers, exclusive of reservoirs, and provided the foundation for the present Pallid Sturgeon Population Assessment Program (PSPAP). Data used in such studies are frequently zero inflated. To address this issue, the zero‐inflated Poisson (ZIP) model was applied. This follow‐up study is based on PSPAP data collected up to 15 years later along with new understanding of how habitat characteristics among and within bends affect habitat use of fish species targeted by PSPAP, including pallid sturgeon. This work demonstrated that a large‐scale, large‐river, PSPAP‐type monitoring program can be an effective tool for assessing population trends and habitat usage of large‐river fish species. Using multiple gears, PSPAP was effective in monitoring shovelnose and pallid sturgeons, sicklefin, shoal and sturgeon chubs, sand shiner, blue sucker and sauger. For all species, the relationship between environmental variables and relative abundance differed, somewhat, among river segments suggesting the importance of the overall conditions of Upper and Middle Missouri River and Lower Missouri and Kansas rivers on the habitat usage patterns exhibited. Shoal and sicklefin chubs exhibited many similar habitat usage patterns; blue sucker and shovelnose sturgeon also shared similar responses. For pallid sturgeon, the primary focus of PSPAP, relative abundance tended to increase in Upper and Middle Missouri River paralleling stocking efforts, whereas no evidence of an increasing relative abundance was found in the Lower Missouri River despite stocking. Copyright © 2014 John Wiley & Sons, Ltd.     

Modeling and analysis of effects of precipitation and vegetation coverage on runoff and sediment yield in Jinsha River Basin

This paper focuses on the effects of precipitation and vegetation coverage on runoff and sediment yield in the Jinsha River Basin. Results of regression analysis were taken as input variables to investigate the applicability of the adaptive network-based fuzzy inference system (ANFIS) to simulating annual runoff and sediment yield. Correlation analysis indicates that runoff and sediment yield are positively correlated with the precipitation indices, while negatively correlated with the vegetation indices. Furthermore, the results of stepwise regression show that annual precipitation is the most important factor influencing the variation of runoff, followed by forest coverage, and their contributions to the variation of runoff are 69.8% and 17.3%, respectively. For sediment yield, rainfall erosivity is the most important factor, followed by forest coverage, and their contributions to the variation of sediment yield are 49.3% and 24.2%, respectively. The ANFIS model is of high precision in runoff forecasting, with a relative error of less than 5%, but of poor precision in sediment yield forecasting, indicating that precipitation and vegetation coverage can explain only part of the variation of sediment yield, and that other impact factors, such as human activities, should be sufficiently considered as well.     

Fishing community preferences and willingness to pay for alternative developments of ecosystem‐based fisheries management (EBFM) for Lake Naivasha,Kenya

Ecosystem‐based fisheries management (EBFM) is an important complement to existing fisheries management approaches to maintain ecosystem health and function; to translate goals and aspirations for sustainability into operational objectives, the preferences of the fishing communities should be considered for successful implementation of EBFM. This study analysed the preferences of the fishing community for alternative EBFM developments for Lake Naivasha, Kenya, and estimated the willingness to pay, using a choice experiment approach. Protection of fish breeding grounds, improving tilapia fish abundance and accessibility of fishing zones were identified as relevant EBFM attributes for the choice experiment. A monetary attribute (payment for fishing permit) was also included. In addition to a conditional logit model, mixed logit models are estimated to account for heterogeneity in preferences. This study results indicated fishing communities are most concerned about tilapia fish abundance and protection of fish breeding grounds. The welfare measures reveal that members of the Lake Naivasha fishing community are willing to pay a considerable sum of money for ecosystem services improvement, relative to their low income derived from fishing. These study findings highlighted that evaluating the preferences of the fishing community and valuing the fishery at an ecosystem level are vital to prioritize and choose between alternative interventions for sound implementation of EBFM.     

沂河流域临沂市农业面源污染定量估算及特征解析

为厘清沂河流域上游临沂市农业面源污染排放时空特征及主要污染来源贡献,采用GIS与排污系数结合法定量估算研究区各类污染源中总氮(TN)、总磷(TP)、化学需氧量(COD)的排放量和排放强度。结果表明：农业面源污染物TN和TP排放量呈“先增后减”,COD排放量呈“先增加后平稳”的变化趋势,其中畜禽养殖业源为主要污染源,对TN、TP、COD的排放贡献率均高于80%,COD为首要污染物,对污染物总排放量的贡献率为41.09%。从空间分布来看,沂南、临沭、沂水、费县为污染物排放重度污染县,可考虑作为农业面源污染的优先控制区进行重点治理。建议研究区下一步重点加强畜禽养殖的排放治理,尤其是COD的减排,同时合理规划养殖规模,加强生态养殖和清洁养殖处理,对畜禽养殖污染进行有效控制。研究成果可为临沂市农业面源污染分区治理以及沂河流域农业面源污染防控提供科学依据。     

沣河流域水质的时空对比分析

沣河流域水质评价是西安市水资源开发和管理的前提,探究沣河水质时空变化特征可以为西安市的水资源利用和科学开发治理提供依据.采用单因子评价法、灰色关联分析法、内梅罗指数法和模糊综合评价法对沣河水质状况进行评价.结果 表明:沣河流域内超标指标主要为TN、TP和NH3—N,水质污染程度整体表现为中游＞下游＞上游,监测断面水质最...     

稀疏样本下冬春季月平均气温空间插值研究——以新疆玛纳斯河流域为例

针对我国典型高寒山区——新疆天山中段玛纳斯河流域积雪-融雪过程模拟中气温空间数据的制备问题,以气象站点稀少的玛纳斯河流域为研究区域,利用最小二乘相关分析法开展了冬、春季(2015年11月-2016年4月)气温环境变量分析,通过共线性检测确定了纬度、海拔、坡度、坡向、NDVI 5个环境变量组成了最优因子集,构建了基于广义回归神经网络(GRNN)的月平均气温空间插值模型。采用区域内139个站点中的119个观测站点数据作为训练数据对GRNN模型进行训练,确定了冬、春季6个月的区域气温空间插值模型。利用剩余的20个观测站点数据作为检验样本,以均方根误差(RMSE)和平均相对误差(MRE)为评价指标,对模型的回归误差进行分析。结果表明:本模型6个月的平均RMSE值为1. 46,优于传统的地理加权回归克里金(GWRK)方法(其平均RMSE值为2. 22)。此外,从不同月份的气温空间插值分布图来看,本文模型空间插值后的气温变化趋势与实际变化趋势一致。从气温的空间分布情况来看,各空间点的气温与其海拔高程呈正相关,且随地表覆盖类型变化。这也表明本文提出的插值策略并组合建立的GRNN模型对于稀疏气象站点条件下的气温空间插值精度更高,一致性较好。     

Targeting lateral connectivity and morphodynamics in a large river‐floodplain system: The upper Rhine River

As a consequence of historical damming and channelization, most large rivers are disconnected from their floodplains, which therefore endure severe deficits in fluvial dynamics. Regaining some degree of lateral connectivity can lead to improved geomorphological and biological interactions. Yet, it is necessary to take into account limitations posed by current uses and legislation. This study presents a methodological approach to the selection of a realistic restoration target for a heavily modified large river segment, the free‐flowing Upper Rhine River downstream of Iffezheim dam (France–Germany border), based on the analysis of the existing biogeomorphic deficits, constraints set by human uses, and previous restoration experiences. To achieve the selected restoration target, proposed scenarios include embankment removal, bank lowerings, and side channel widenings with the aim of increasing lateral hydrological connectivity and promoting morphodynamics (bank erosion in lateral channels) that allow for the renewal of floodplain habitats. Results from 2‐D hydraulic simulations allow for a sensitivity analysis, comparing the current situation with the proposed scenarios, through parameters such as shore length of side channels actively connected at both ends to the main channel (eupotamon), and shear stress as a proxy for initiation of gravel erosion. Outcomes indicate that the two proposed restoration scenarios would succeed in reconnecting side channels and in increasing areas prone to substrate erosion, while maintaining flood protection and the heaviest navigation use among European rivers. The presented approach aids in the assessment of potential large river restoration scenarios and, thus, in the discussion of water management strategies.