River System Research Articles

Distribution of invasive scud, Apocorophium lacustre (Vanhoffen, 1911) in the Illinois Waterway, USA: Do habitat and water quality variables influence spatial distribution and relative abundance?

Apocorophium lacustre – a species of benthic amphipod native to American and European estuaries along the North Atlantic Ocean – has rapidly expanded outside of its native range and is now established in the Illinois, Upper Mississippi, and Ohio river systems, USA. A. lacustre is considered high risk for colonization and disruption of the Laurentian Great Lakes’ benthic communities. To further our understanding of factors influencing A. lacustre distribution and its threat to the Great Lakes, zoobenthic and habitat data were collected from colonization samplers (i.e., rock bags) deployed at 370 sites along the Illinois Waterway. A. lacustre was found in the lower six pools of the Illinois Waterway and was the most abundant amphipod collected in those pools. Our results parallel other studies in that A. lacustre was not observed upstream of Dresden Island Pool, but A. lacustre was found ~11 km farther upstream of any previous records. Generalized linear mixed effects modeling indicated that parameters pertaining to food availability, water quality, and impoundment influenced A. lacustre abundance. Model averaging identified five statistically significant variables: A. lacustre abundance was negatively associated with turbidity, fluorescent dissolved organic matter, and vegetation density and positively associated with temperature and downstream distance (i.e., closer to the next downstream dam). Our findings of what factors influence A. lacustre abundance should be of broad interest to risk assessment and invasion forecasting in other regions where A. lacustre have been or may be introduced.

A Sand Boil Database for Piping Risk Management in the Po River, Italy

Sand boil formation at the toe of river embankments is the typical manifestation of the initiation and progression of an internal erosion process known as backward erosion piping, which is recognized to be a major concern in many river systems worldwide. In Italy, more than 130 sand boils have been detected along the Po River, many of them experiencing recurrent reactivations during high-water events. In recent years, as part of the activities of the European project LIFE SandBoil, the Italian authority responsible for flood protection and flood damage reduction along the Po River has implemented a GIS-based web application to catalogue the sand boils observed in its operating area. The resulting database allows keeping records of a comprehensive and varied set of information, in terms of predisposing factors, initiation conditions and surface effects. Taking as a reference a well-documented cross-section of the Po River prone to piping, this paper describes the main features of this versatile and flexible tool, whose long-term aim is to support vulnerability studies and the development of risk maps against piping. The database, which might also accommodate data from different river basins, is thus meant to help in flood risk management, by suggesting priorities for the implementation of mitigation measures and allowing the monitoring of intervention effectiveness.

What is happening with frequency and occurrence of the maximum river discharges in Bosnia and Herzegovina?

In this study, we explored the frequency and occurrence rate of maximum river discharges in the Una and Sana rivers, to understand hydrological variations amidst climate change. We categorized maximum discharges into severe (Una River M1 > 98.2 m3/s; Sana River M1 > 118.2 m3/s) and extreme (Una River, M2, > 123.4 m3/s; Sana River M2 > 246.4 m3/s) events, and identified trends in these events, crucial for assessing environmental impacts. Our findings reveal a nuanced pattern: both rivers experience an increase in severe events from 58 to 55 and 56 to 54 days return period respectively, indicating complex hydrological dynamics. The trends underscore the significant shifts in annual event occurrences, the evolving nature of river systems and underscore the necessity for adaptive management strategies.

Multiple secondary contacts and historic hybridization between glacial lineages of charr (Salvelinus, Salmonidae) in northeastern Asia

AbstractArctic regions of northeastern Asia represent areas of secondary contact of the glacial phylogenetic lineages of charrs belonging to the genus Salvelinus (Salmoniformes: Salmonidae). However, the post‐glacial dispersion of charr across Arctic regions is poorly understood, as knowledge of populations from Chukotka and its neighbouring areas remains limited. Specifically, there is no clear understanding of which charr species inhabit significant regions of Chukotka from the sea coasts to the Kolyma drainage. In this study, we explored the affiliation of lacustrine charrs from the Chukotka area with (1) the Arctic lineage of Taranetz' charr (Salvelinus taranetzi); (2) the Bering lineage of Northern Dolly Varden (Salvelinus malma malma) and (3) the Siberia and Atlantic lineages of Arctic charr (Salvelinus alpinus). We analysed sequence variation of the mitochondrial DNA control region (mtDNA CR; 960 base pairs) and genotyped seven microsatellite loci of nuclear DNA from charr collected at 13 sampling sites. We found different consequences of secondary contact: (1) complete fixation of introgressed mtDNA (mitochondrial capture) and (2) preservation of several mtDNA lineages with the absence of contemporary gene flow between resident populations. Combining the distribution patterns, phylogenetic network topology and knowledge of the glaciation history of the region, we propose two zones of secondary contact of the glacial lineages in Chukotka–Kolima‐Chukotka River system and Paleo‐Amguema River–from where charrs with introgressed genomes spread throughout this range. However, in some cases, the process of foreign mtDNA capture likely occurs in a more localised manner.

Description of a new species of Cottus Linnaeus (Cottidae) from the Western Dvina / Daugava River system, Baltic Sea basin, based on integrative taxonomy

In the genus Cottus (family Cottidae), 72 species are known. Of these, 37 species are found in North America, 17 in Asia, and 18 in Europe. Over the past 18 years, nine new species have been described from Western and Central Europe, two from Eastern part of this continent. Also, the validity of two Eastern European species was confirmed. In the Western Dvina / Daugava River system (Baltic Sea basin), Cottus dorofeevi sp. nov. was found. To describe this species, an integrative approach was used that combines morphological and molecular methods. The new species differs from other species of the genus Cottus by a combination of morphological characters. Taxonomically the most conspicuous features are: flattened shape of head; long pelvic fins (reaching anus); incomplete trunk canal of lateral line with 25-27 pores; presence of melanophores on ventral side of body and fins. Genetically, C. dorofeevi sp. nov. is sister to C. koshewnikowi. Haplotypes (CR) of C. dorofeevi sp. nov. are differentiated from haplotypes of other European species of the genus Cottus by genetic distances between 1.3% and 3%.

Clarity tubes as effective citizen science tools for monitoring wastewater treatment works and rivers.

Improved freshwater resource management requires the implementation of widespread, effective, and timely water quality monitoring. Conventional monitoring methods are often inhibited by financial, infrastructural, and human capacity limitations, especially in developing regions. This study aimed to validate the citizen-scientist-operated transparency or clarity tube (hereafter "clarity tube") for measuring water clarity as a proxy for total suspended solids (TSS) concentration, a critical quality metric in river systems and wastewater treatment works (WWTW) effluent in Southern Africa. Clarity tubes provided a relatively accurate and precise proxy for TSS in riverine lotic systems and WWTW effluent, revealing significant inverse log-linear relationships between clarity and TSS with r2 = 0.715 and 0.503, respectively. We demonstrate that clarity-derived estimates of TSS concentration (TSScde) can be used to estimate WWTW compliance with WWTW effluent TSS concentration regulations. The measurements can then be used to engage with WWTW management, potentially affecting WWTW performance. Overall, these findings demonstrate the usefulness of clarity tubes as low-cost, accessible, and easy-to-use citizen science tools for high spatial and temporal resolution water quality monitoring, not only in rivers in Southern Africa but also in WWTW effluent for estimating compliance, with strong global relevance to the sustainable development goals (SDGs). Integr Environ Assess Manag 2024;00:1-10. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

A Numerical Study on the Influence of Riparian Vegetation Patch on the Transportation of Suspended Sediment in a U-Bend Channel Flow

Bend sections are ubiquitous in natural sandy river systems. This study employs Computational Fluid Dynamics–Discrete Phase Model (CFD-DPM) methodology to analyze particle transport dynamics in U-bend channel flows, focusing on the distinctions between partially vegetated (Case No.1) and non-vegetated (Case No.2) scenarios. The research aims to unravel the intricate relationships among bending channel-induced secondary flow, vegetation blockage, and particle aggregation, employing both quantitative and qualitative approaches. (I) The key findings reveal that vegetation near the inner walls of curved channels markedly diminishes the intensity of secondary circulation. This reduction in circulation intensity is observed not only within vegetated areas but also extends to adjacent non-vegetated zones. Additionally, the study identifies a close correlation between vertical vortices and particle distribution near the channel bed. While particle distribution generally aligns with the vortices’ margin, dynamic patch-scale eddies near vegetation patches induce deviations, creating wave-like patterns in particle distribution. (II) The application of the Probability Density Function (PDF) provides insights into the radius-wise particle distribution. In non-vegetated channels, particle distribution is primarily influenced by secondary flow and boundary layers. In contrast, the presence of vegetation leads to a complex mixing layer, altering the particle distribution pattern and maximizing PDF values in non-vegetated free flow subzones. (III) Furthermore, the research quantifies spatial–temporal sediment heterogeneity through PDF variance. The findings demonstrate that variance in non-vegetated channels increases towards the outer wall in bending regions. Vegetation-induced turbulence causes higher variance, particularly in the mixing layer subzone, underscoring the significance of eddy size in sediment redistribution. (IV) The study of vertical concentration profiles in vegetated U-bend channels offers additional insights, while secondary flow in non-vegetated channels facilitates upward sediment transport and vegetation presence, although increasing the Turbulent Kinetic Energy (TKE), restricts channel space, and impedes secondary flow, thereby reducing vertical particle suspension. Sediment concentrations are found to be higher in the lower layers of vegetated bends, contrary to the pattern in non-vegetated bends. These findings highlight the complex interplay between vegetation, secondary flow, and sediment transport, illustrating the reduced effectiveness of secondary flow in promoting vertical particle transportation in bending channels due to the vegetation obstruction.

Indigenous Water Engineering and Aquaculture Systems in Australia: The Budj Bim Cultural Landscape and Baiame’s Ngunnhu (the Brewarrina Aboriginal Fish Traps)

In Australia, First Peoples have practiced sustainable forms of water management for millennia. They have done so by respectfully caring for Country through their use of engineering and maintenance processes, including sophisticated fish and eel trapping structures and weir systems. Some of the largest continuing sites of water engineering and aquaculture in the world are still visible and used by local Aboriginal groups – the Budj Bim in Victoria and Baiame’s Ngunnhu (Brewarrina Aboriginal fish traps) in New South Wales (NSW). Recent scholarship and successful heritage listings, including the World Heritage listing of the Budj Bim Cultural Landscape and work by and with traditional custodians in these river systems, are starting to bring into public discourse and knowledge these sophisticated and important places of global cultural significance. The principles used in the design of these systems, and the social and environmental contexts of their maintenance and convening power over millennia, are particularly important as we navigate new technologically mediated forms of water management today and into the future. These management challenges include communities in Australia and globally working on the importance of significant places, values, rights, justice and voice for Indigenous peoples in building sustainable futures, including through innovation and safe, sustainable and responsible cybernetic approaches to water governance and the SDGs.

Towards biogeomorphic river restoration: Vegetation as a critical driver of physical habitat

AbstractThe current focus of river restoration on flow and sediment transfer without proper consideration of vegetation as a key structuring agent, beyond its stabilising effect, is too simplistic. We contend that vegetation has an essential role in shaping the physical fluvial environment and should be considered equally alongside hydrogeomorphic processes in restoration projects. In support, we introduce engineer plants as important controls, along with flowing water and transported sediments, on the morphodynamics of river systems and associated physical habitat development. The effect of vegetation on channel planform is then summarised, the influence of vegetation on hydrogeomorphic connectivity is outlined, and then the role of vegetation in landform development and habitat provision, as encapsulated in the fluvial biogeomorphic succession model, is described. We then present examples demonstrating how vegetation has contributed to the recovery of degraded rivers through biogeomorphic processes. Finally, we advance the concept of biogeomorphic river restoration by proposing principles to support a closer synthesis of the component sciences and list key areas for practitioners to focus on. Vegetation succession has a significance that goes beyond its physical structure or influence on sediment stability. In many river settings, it is central to channel evolution. The coupled assembly of plant communities and fluvial landforms affect the development of spatially and temporally dynamic habitat through biogeomorphic interactions. Restoration approaches that do not fully consider this dynamic may fail to anticipate river behaviour and recovery trajectories.

Water for Food in the Tigris–Euphrates River System

Water scarcity is an important threat to food security in the Tigris–Euphrates river system. Water scarcity is a huge worldwide problem that results from the rapid increase in water demand, which exceeds the amount of available water. The most significant problems currently affecting countries are food insecurity water scarcity. The Tigris–Euphrates river system countries suffer from different political issues, such as the Syrian war and internal civil conflicts in Iraq. In addition, this area consists of only three countries: Iraq, Syria, and Turkey, but it affects the entire Middle East. Turkey has established many irrigation projects compared to Iraq, which still suffers from the previous American invasion. Therefore, this study examines the Tigris–Euphrates river system (using two countries) to examine the relationship between water scarcity and food security from 1992 to 2020. This study will be conducted using a fixed and random regression approach over 18 years. The results show a negative relationship between water scarcity and food security in the short run, at a 10% significance level, and a long-term positive relationship of 1%. Thus, the use of research and development and the encouragement of investments will help policymakers to develop a nexus between water scarcity and food security.

Variation in macroinvertebrate assemblages and water quality as a test for different levels of ecological impairment across an Ethiopian highland river system

The Ethiopian highlands is an area under high anthropogenic pressure. Despite being a hotspot for freshwater biodiversity, there is no regular monitoring of the ecological status of local rivers. Physicochemical and nutrient water-quality parameters and macroinvertebrate assemblages were sampled monthly from the Megech River and its tributaries from January to March 2021. Sampling locations were designated as being either upstream or downstream of the Gondar City urban area. We tested for temporal (monthly) and spatial (location, river) variation in water quality and spatial (location, river) variation in macroinvertebrate assemblage structure, and examined which water quality parameters were most associated with patterns in macroinvertebrate assemblages. Water quality varied significantly between locations and months, but not between rivers. Water quality differences were particularly driven by higher nutrient, salinity, dissolved solids and conductivity levels downstream, and higher pH and dissolved oxygen levels upstream. Despite macroinvertebrate assemblages being more abundant and diverse downstream, biotic index scores generally indicated slightly increased ecological impairment downstream. There was a clear spatial pattern in macroinvertebrate assemblages between locations. We detected a significant difference between rivers, with pairwise differences between sampling locations, particularly due to high dissimilarity between the upstream and downstream locations of the Angereb, Shinta and Qeha rivers. BIO-ENV Pearson correlations indicated that variation in macroinvertebrate assemblages were mostly explained by dissolved oxygen, salinity and nutrient parameters including nitrate, ammonium, and sulphate. Our findings confirm the need for more rigorous monitoring of Ethiopian highland rivers and improved management of nutrient inputs.

Long-neglected contribution of nitrification to N2O emissions in the Yellow River

Rivers play a significant role in the global nitrous oxide (N2O) budget. However, the microbial sources and sinks of N2O in river systems are not well understood or quantified, resulting in the prolonged neglect of nitrification. This study investigated the isotopic signatures of N2O, thereby quantifying the microbial source of N2O production and the degree of N2O reduction in the Yellow River. Although denitrification has long been considered to be the dominant pathway of N2O production in rivers, our findings indicated that denitrification only accounted for 18.3% (8.2%–43.0%) of the total contribution to N2O production in the Yellow River, with 50.2%–80.2% being concurrently reduced. The denitrification contribution to N2O production (R2 = 0.44, p < 0.01) and N2O reduction degree (R2 = 0.70, p < 0.01) were positively related to the dissolved organic carbon (DOC) content. Similar to urban rivers and eutrophic lakes, denitrification was the primary process responsible for N2O production (43.0%) in certain reaches with high organic content (DOC = 5.29 mg/L). Nevertheless, the denitrification activity was generally constrained by the availability of electron donors (average DOC = 2.51 mg/L) throughout the Yellow River basin. Consequently, nitrification emerged as the primary contributor in the well-oxygenated Yellow River. Additionally, our findings further distinguished the respective contribution of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to N2O emissions. Although AOB dominated the N2O production in the Yellow River, the AOA specie abundance (AOA/(AOA + AOB)) contributed up to 32.6%, which resulted in 25.6% of the total nitrifier-produced N2O, suggesting a significant occurrence of AOA in the oligotrophic Yellow River. Overall, this study provided a non-invasive approach for quantifying the microbial sources and sinks to N2O emissions, and demonstrated the substantial role of nitrification in the large oligotrophic rivers.

A comparative study of the alternative life history of iteroparous salmonids

AbstractThe kelt phase of anadromous iteroparous salmonid life history remains mysterious, particularly aspects of their habitat use and factors influencing survival. Atlantic salmon and sea‐run brown trout were captured in the estuary during their return migration to the Vosso River, Norway, tagged with acoustic transmitters, and tracked in the watershed and estuary in three different years (2020–2023). We found a relatively narrow window of river exit timing among trout that survived overwinter, whereas salmon tended to leave during a more protracted period. Trout preferred overwintering in lakes within the river system, which provided for lower locomotor activity than fish that overwintered in pools in the river according to data from tri‐axial accelerometer transmitters. In contrast, Atlantic salmon tended to spend surprisingly little time in lakes even though the energy expenditure in this habitat is was seemingly lower for salmon that did overwinter in the lake. Our results demonstrate different use of habitat during overwintering and could suggest that measures to protect iteroparous life history strategies of salmonids will differently impact these two iteroparous salmonids.

Sediment source areas and the role of floods in sediment mixing on the Letaba River, South Africa

ABSTRACT The morphodynamics of rivers in semiarid environments tend to be controlled by episodic flood events, but the precise nature of sedimentary processes and sediment source areas within catchments affected by episodic floods remains not well understood. This study presents geomorphological, sedimentary and mineralogical data from different river reaches along the semiarid Letaba River within Kruger National Park, northeast South Africa. Geomorphological and sedimentary data were used to evaluate river morphodynamic behaviour and identify the major controls on landform development. Mineralogical data (heavy minerals and trace elements) were examined from surface sediment samples from different river reaches to determine the potential source areas for sediment reworking within the catchment (channel bank, channel bed, tributaries) for flood-transported sediments. Results of this analysis on downstream reaches show catchment-averaged sediment contributions from the channel bed of 42.5%, tributaries of 35%, and channel bank of 22.5%. These sediment contributions likely arise as a result of the different flow conditions experienced in different locations of the river system during floods. However, there is significant variability between samples from individual reaches, likely related to valley width and bedrock vs sediment availability. The contributions of river sediments from different sources are conceptually developed through a model of sediment source variability at different hydrodynamic stages. This highlights the role of floods in reactivating non-perennial tributaries and adding new sediment into the main channel. Measurements of perennial channel storage, therefore, do not give the whole picture of total sediment availability or activation during floods.

Monthly hydraulic geometry relationship quantification with environmental LAI by utilizing sentinel data: A case in Jingjiang reach of the Yangtze River

This study presents a novel approach for quantifying the dynamics of monthly hydraulic geometry relationships in the Jingjiang reach of the Yangtze River by integrating leaf area index (LAI) data as an indicator of riparian vegetation. A comprehensive system of ordinary differential equations (ODEs) couples traditional power-law hydraulic geometry equations with LAI, capturing the influence of erosion control on channel morphology. The periodic delayed response theory and automatic differentiation techniques are employed to enhance the modeling framework’s capabilities. Calibration and verification demonstrate the models’ effectiveness in capturing overall trends in discharge, width, and depth dynamics, outperforming traditional constant-parameter approaches. However, model predictive abilities are limited under extreme climate conditions due to training on normal climate data. Key assumptions, including the periodic delayed response theory’s neglect of peak discharges, simplified representation of artificial cut-offs, and reliance on remotely sensed data with limited local validation, introduce uncertainties. The proposed modeling framework shows potential for broader application to other river systems with appropriate adjustments. Future research could incorporate additional environmental factors, integrate models across scales, couple with advanced simulation techniques, and expand stability assessments beyond the riverbed index. By addressing related challenges, this integrated approach lays a foundation for enhancing understanding of river morphodynamics and channel stability.

A state-of-the-art review of normal and extreme flow interaction with spur dikes and its failure mechanism

River protection structures, especially spur dikes, play a vital role in the hydrodynamic and morphological changes in a river system. Since the earliest days, numerous studies have been carried out to understand the flow characteristics around spur dikes by varying the spacing between them, the length, the shape, the permeability, and the submergence. Despite several studies, knowledge of flow characteristics around spur dikes is still poorly understood, resulting in damages and failures worldwide. Furthermore, such failures get aggravated under extreme conditions like floods, land-slide-induced surges and tidal bores. Therefore, this state-of-the-art review paper provides a comprehensive account of relevant studies on the flow interaction and its characteristics in the vicinity of spur dikes during normal and extreme scenarios. Possible failure mechanisms with a detailed examination of scour in the proximity of spur dikes are deliberated. Suitable design features and international standards of various types of spur dikes are appraised through this comprehensive review. Furthermore, we also identified a number of research gaps that need immediate attention. This review paper, as a whole, provides concrete knowledge of the flow interaction with spur dikes and design components of spur dikes, thereby helping researchers to understand the advancement in the research area and providing hydraulic engineers with guidance for designing the spur field at a specific site based on the requirements.

Application of environmental DNA metabarcoding to identify fish community characteristics in subtropical river systems

AbstractFish are vital in river ecosystems; however, traditional investigations of fish usually cause ecological damage. Extracting DNA from aquatic environments and identifying DNA sequences offer an alternative, noninvasive approach for detecting fish species. In this study, the effects of environmental DNA (eDNA), coupled with PCR and next‐generation sequencing, and electrofishing for identifying fish community composition and diversity were compared. In three subtropical rivers of southern China, fish specimens and eDNA in water were collected along the longitudinal (upstream–downstream) gradient of the rivers. Both fish population parameters, including species abundance and biomass, and eDNA OTU richness grouped 38 sampling sites into eight spatial zones with significant differences in local fish community composition. Compared with order‐/family‐level grouping, genus‐/species‐level grouping could more accurately reveal the differences between upstream zones I−III, midstream zones IV−V, and downstream zones VI–VIII. From the headwaters to the estuary, two environmental gradients significantly influenced the longitudinal distribution of the fish species, including the first gradient composed of habitat and physical water parameters and the second gradient composed of chemical water parameters. The high regression coefficient of alpha diversity between eDNA and electrofishing methods as well as the accurate identification of dominant, alien, and biomarker species in each spatial zone indicated that eDNA could characterize fish community attributes at a level similar to that of traditional approaches. Overall, our results demonstrated that eDNA metabarcoding can be used as an effective tool for revealing fish composition and diversity, which is important for using the eDNA technique in aquatic field monitoring.

Spatial distribution of benthic taxonomic and functional diversity in the Yellow River Basin: From ecological processes to associated determinant factors

One of the fundamental objectives in ecology is to investigate the ecological processes and associated factors governing the abundance and spatial distribution patterns of biodiversity. However, the reaction of biological communities to environmental degradation remains relatively unknown, even for ecologically crucial communities like macroinvertebrates in aquatic ecosystems. Here, we sampled 117 locations to quantify relative contributions of geographical and environmental factors, including water quality, land use, climate, and hydrological factors, to determine the absolute and relative compositions of macroinvertebrate communities and their spatial distribution in the Yellow River Basin (YRB), the sixth-longest river system on Earth. We assessed relative roles of species sorting and dispersal in determining macroinvertebrate community structure along YRB. Our results demonstrated that alpha and beta diversity indices showed an increase from the up- to low-reaches of YRB. The middle and low-reaches exhibited elevated species diversity and both regions exhibited relatively stable community compositions. The biodiversity of macroinvertebrates was influenced by a combination of geographical factors and environmental variables, with environmental factors predominantly serving as the principal determinants. Results of multiple linear regression and variance decomposition showed that the effect of environmental factors was approximately three times greater than that of spatial factors. These findings provide support for the hypothesis that species sorting, driven by environmental gradients, plays a significant role in shaping the community structure of macroinvertebrates in running water ecosystems at the basin scales. Moreover, the factors contributing to substantial shifts in biodiversity across different segments of YRB indicate that distinct river sections have been influenced by varying stressors, with downstream areas being more susceptible to the impacts of water pollution and urbanization resulting from human activities.

Contribution of carbonate-derived dissolved inorganic carbon into autochthonous particulate organic carbon in two small temperate Korean rivers (Geum and Seomjin)

In this study, we estimated the contributions of carbonate mineral weathering to dissolved inorganic carbon (DIC) and carbonate-derived DIC to autochthonous particulate organic carbon (POC) in two temperate Korean rivers. We combined stoichiometric and stable carbon isotopic approaches to calculate the contribution of autochthonous POC, considering diverse riverine DIC sources. We collected surface water samples from May 2016 to May 2018 and analyzed the major ion composition of rivers along with the concentrations and stable carbon isotopes of DIC. Our estimates showed that the relative abundances of carbonate mineral weathering (0.41±0.11 in the Geum River and 0.43±0.07 in the Seomjin River) were only slightly lower than those of silicate mineral weathering (0.59±0.1 in the Geum River and 0.57±0.07 in the Seomjin River). The resulting percentage contributions of DIC derived from the carbonate mineral weathering to riverine autochthonous POC, if we consider the additional DIC sources of atmospheric and soil-derived CO2, were 10±3% in the Geum River and 2±1% in the Seomjin River. The calculated annual fluxes of carbonate-derived DIC for 2016–2018 were 23.2±0.3 Gg C yr–1 in the Geum River and 1.1±0.4 Gg C yr–1 in the Seomjin River. Moreover, the calculated annual fluxes of carbonate-derived POC were 3.6±0.5 Gg C yr–1 in the Geum River and 0.1±0.7 Gg C yr–1 in the Seomjin River. Accordingly, our study provides the first insight into the contribution of carbonate-derived DIC to riverine autochthonous POC in small temperate Korean river systems, dominated by silicate rocks.

Yangtze and the Rhine, two Major Rivers Systems

This introduction to the articles about the Rhine and the Yangtze as well as transport on these rivers emphasizes how innovation plays a role throughout both subjects for this collection. In two articles here, this innovation took the form of the movement of a capitalist, business mentality from the coastal areas, where there was already plenty of seafaring and trade, to the interior via the river. In the eighteenth century, this was the case both along the Rhine and along the Yangtze as can be seen from the articles by Ralf Banken and Yao Chen. The articles by Blussé and Klemann, rather, focus on more concrete technical innovation. Blussé shows how similar circumstances, independently of each other, led to similar technical innovations in the Yangtze and Rhine deltas. Klemann looks at the consequences of nineteenthcentury mechanization for Rhine navigation, especially for the small Rhine skippers.