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Prediction of dissolved oxygen concentration in hypoxic river systems using support vector machine: a case study of Wen-Rui Tang River, China
Accurate quantification of dissolved oxygen (DO) is critically important for managing water resources and controlling pollution. Artificial intelligence (AI) models have been successfully applied for modeling DO content in aquatic ecosystems with limited data. However, the efficacy of these AI models in predicting DO levels in the hypoxic river systems having multiple pollution sources and complicated pollutants behaviors is unclear. Given this dilemma, we developed a promising AI model, known as support vector machine (SVM), to predict the DO concentration in a hypoxic river in southeastern China. Four different calibration models, specifically, multiple linear regression, back propagation neural network, general regression neural network, and SVM, were established, and their prediction accuracy was systemically investigated and compared. A total of 11 hydro-chemical variables were used as model inputs. These variables were measured bimonthly at eight sampling sites along the rural-suburban-urban portion of Wen-Rui Tang River from 2004 to 2008. The performances of the established models were assessed through the mean square error (MSE), determination coefficient (
R
2
), and Nash-Sutcliffe (NS) model efficiency. The results indicated that the SVM model was superior to other models in predicting DO concentration in Wen-Rui Tang River. For SVM, the MSE,
R
2
, and NS values for the testing subset were 0.9416 mg/L, 0.8646, and 0.8763, respectively. Sensitivity analysis showed that ammonium-nitrogen was the most significant input variable of the proposal SVM model. Overall, these results demonstrated that the proposed SVM model can efficiently predict water quality, especially for highly impaired and hypoxic river systems.
Journal Article
A Bronze Age landscape in the Russian steppes : the Samara Valley Project
\"The Samara Valley Project (SVP) was a US-Russian archaeological investigation in the steppes east of Samara, Russia between 1995 and 2002. This 21-author volume is the project's final report. It describes the changing organization and subsistence resources of pastoral steppe economies from the Eneolithic (4500 BC) through the Late Bronze Age (1900-1200 BC) across a steppe-and-river valley landscape in the middle Volga region, with particular attention to the role of agriculture during the unusual episode of sedentary, settled pastoralism that spread across the Eurasian steppes with the Srubnaya (Timber-Grave) and Andronovo cultures (1900-1200 BC). We excavated a permanently occupied Srubnaya domestic residence at Krasnosamarskoe dated about 1900-1700 BC and a series of contemporaneous seasonal Srubnaya herding camps. This is the first English-language monograph that describes seasonal and permanent LBA settlements in the Russian steppes. We analyze economic resources (wild and domesticated plants and animals, copper mining and metallurgy) and their seasonal exploitation, supplemented by human biological data from Eneolithic-through-Bronze Age pathologies related to diet, health, and activities, as well as dietary stable isotopes, cranio-facial measurements, and ancient DNA. Three important discoveries were that agriculture played no role in the LBA diet across the region, a surprise given the settled residential pattern; second that a winter ritual involving dog and wolf sacrifices, possibly related to male initiation ceremonies, occurred uniquely at Krasnosamarskoe; and third that overlapping spheres of obligation, cooperation, and affiliation operated at different scales to integrate groups defined by politics, economics, and ritual behaviors\"-- Provided by publisher.
Book
Governing for local livelihoods in transboundary river systems: insights from the Cubango-Okavango River Basin
Climate change will present new challenges for transboundary governance of international river basins, many of which will experience increasing levels of environmental variability in the coming decades. Failure to adequately respond to these challenges will increase vulnerability for people across the globe who rely on these river systems for their livelihoods. To be effective, governance systems will need to embrace uncertainty, increase international cooperation, and authentically engage local actors in decision-making. This paper considers the potential for transnational governance that accounts for local livelihoods by presenting findings from qualitative research in Namibia and Botswana, two of the three countries located in the Cubango-Okavango River Basin of Southern Africa. Findings show the importance of local livelihoods for communities in the basin, which have been historically overlooked by governance systems, and which now face increasing threats from development and climate change. The paper illustrates how these livelihoods are governed by a complex institutional arrangement that includes national governments inclined to protect their own interests and a transnational governance body whose mission is to coordinate decision-making across the basin to support sustainable development. The paper concludes with a call for increased attention to the impacts of governance decisions on the livelihoods of river basin communities, with insights for the Cubango-Okavango River Basin specifically, as well as for international river basins more broadly.
Journal Article
Impact of global climate change induced variations in reservoir-river systems on fish habitats
Global climate change (GCC) and reservoir operations impact basin-scale hydrological conditions, altering river-scale hydrodynamics and aquatic habitats. This study designed a numerical evaluation methodology framework that integrates GCC, downscaling, hydrological, hydrodynamic, water temperature (WT), and habitat suitability models across global, basin, river, and habitat to predict the impacts of GCC on the hydrology and aquatic ecological environment of the reservoir-river system (RRS). The framework was applied to the Xiaolangdi Reservoir (XLDR) and its downstream river reach. In the study area, runoff, water level, WT, and weighted usable area (WUA) were predicted for the baseline and four scenarios, and the impact of GCC on the inflow, WT, and WUA of the RRS was evaluated. The results proved that the Soil and Water Assessment Tool (SWAT) model, the statistical downscaling model (SDSM), three-dimensional (3D) and two-dimensional (2D) hydrodynamic, and WT models met requirements. Runoff remained sufficient to meet system demands under the four GCC scenarios. WT surface, middle, and bottom in the XLDR showed increasing trends. Compared to the baseline scenario, the decrease in WUA for the spawning and juvenile Yellow River carp (
Cyprinus carpio haematopterus
) (YRC) was mainly influenced by hydrodynamic conditions and rising WT changes. The impacts of GCC were likely to exacerbate the adverse effects of reservoir regulation on YRC’s breeding season.
Journal Article
Global Patterns and Changes of River Backwater Points over Two Decades
The study of river backwater points (bpts) is pivotal for understanding the interactions between riverine and coastal systems, including brackish water dynamics, coastal flooding, and ecosystem processes. Despite extensive research, the global spatio-temporal dynamics of bpts, particularly in rivers with minimal human intervention, remains underexplored. This study investigates backwater lengths and shifts in 18 major global rivers (discharge > 5000 m3/s) from 2000 to 2020, uncovering significant hydrological and geographical patterns. In 2000, backwater lengths ranged from 113.16 km (Salween) to 828.75 km (Amur), with bpts consistently positioned upstream of apex points. By 2020, all rivers exhibited upstream retreats of their bpts, ranging from 10.43 km (Salween) to 132.51 km (Amazon), and retreat ratios typically falling between 0% and 20%. The Salween, Niger (60%), and Irrawaddy (38%) demonstrated the most significant proportional shifts. Geographical transitions of bpts varied widely: rivers such as the Ganges and Amur shifted toward urbanized areas, while the Amazon and Orinoco remained in remote regions, reflecting the differential impact of human activity and natural processes. There was a general correlation between backwater length and river discharge, with exceptions like the Amur indicating the influence of other factors such as geomorphic settings and sediment dynamics. While sea-level rise (0.019–0.115 m) affected estuarine conditions, it showed no consistent relationship with bpt retreat at the global scale, but a regional-scale analysis indicates that sea-level rise can lead to the retreat of bpts for those rivers with macro-tidal environments and high sediment yields with less human intervention, suggesting localized interactions dominate backwater dynamics. These findings highlight the complex interplay of environmental and anthropogenic pressures on global river systems. They provide a critical foundation for advancing hydrological modeling, improving river management strategies, and understanding the broader implications of spatio-temporal bpt dynamics under changing climatic and human influences.
Journal Article
Accounting for environmental flow requirements in global water assessments
As the water requirement for food production and other human needs grows, quantification of environmental flow requirements (EFRs) is necessary to assess the amount of water needed to sustain freshwater ecosystems. EFRs are the result of the quantification of water necessary to sustain the riverine ecosystem, which is calculated from the mean of an environmental flow (EF) method. In this study, five EF methods for calculating EFRs were compared with 11 case studies of locally assessed EFRs. We used three existing methods (Smakhtin, Tennant, and Tessmann) and two newly developed methods (the variable monthly flow method (VMF) and the Q90_Q50 method). All methods were compared globally and validated at local scales while mimicking the natural flow regime. The VMF and the Tessmann methods use algorithms to classify the flow regime into high, intermediate, and low-flow months and they take into account intra-annual variability by allocating EFRs with a percentage of mean monthly flow (MMF). The Q90_Q50 method allocates annual flow quantiles (Q90 and Q50) depending on the flow season. The results showed that, on average, 37% of annual discharge was required to sustain environmental flow requirement. More water is needed for environmental flows during low-flow periods (46–71% of average low-flows) compared to high-flow periods (17–45% of average high-flows). Environmental flow requirements estimates from the Tennant, Q90_Q50, and Smakhtin methods were higher than the locally calculated EFRs for river systems with relatively stable flows and were lower than the locally calculated EFRs for rivers with variable flows. The VMF and Tessmann methods showed the highest correlation with the locally calculated EFRs (R2=0.91). The main difference between the Tessmann and VMF methods is that the Tessmann method allocates all water to EFRs in low-flow periods while the VMF method allocates 60% of the flow in low-flow periods. Thus, other water sectors such as irrigation can withdraw up to 40% of the flow during the low-flow season and freshwater ecosystems can still be kept in reasonable ecological condition. The global applicability of the five methods was tested using the global vegetation and the Lund-Potsdam-Jena managed land (LPJmL) hydrological model. The calculated global annual EFRs for fair ecological conditions represent between 25 and 46% of mean annual flow (MAF). Variable flow regimes, such as the Nile, have lower EFRs (ranging from 12 to 48% of MAF) than stable tropical regimes such as the Amazon (which has EFRs ranging from 30 to 67% of MAF).
Journal Article
Numerical Modeling of Instantaneous Spills in One-dimensional River Systems
Modeling the fate and transport of spills in rivers is critical for risk assessment and instantaneous spill response. In this research, a one-dimensional model for instantaneous spills in river systems was built by solving the advection-dispersion equation (ADE) numerically along with the shallow water equations (SWEs) within the MATLAB environment. To run the model, the Ohio River’s well-known accidental spill in 1988 was used as a field case study. The verification process revealed the model’s robustness with very low statistic errors. The mean absolute error (MAE) and root mean squared error (RMSE) relative to the absorbed record were 0.0626 ppm and 0.2255 ppm, respectively. Results showed the spill mass distribution is a function of the longitudinal dispersion coefficient and the mass decay rate. Increasing the longitudinal dispersion coefficient reduces the spill impact widely, for instance after four days from the mass spill the maximum concentration decreased from 0.846789 to 0.486623 ppm, and after five days it decreased from 0.332485 to 0.186094 ppm by increasing the coefficient from 15 to 175 m2/sec. A similar reduction was achieved by increasing the decay rate from 0.8 to 1.2 day-1 (from 0.846789 to 0.254274 ppm and from 0.332485 to 0.0662202 ppm after four and five days, respectively). Thus, field measurements of these two factors must be taken into account to know the spill fate in river systems.
Journal Article
A global analysis on the relationship between water retention time and dissolved carbon across inland waters
The transport of dissolved carbon (DC) from inland waters to the ocean is an important component of the global carbon cycle. However, how water retention time (WRT) affects the concentration and flux of DC in inland waters remains unclear. In this study, we collected 613 data points for WRT, the concentration and flux of dissolved organic carbon (DOC), inorganic carbon (DIC) and dissolved CO2 from 587 field studies and 26 model simulations worldwide. We found that the longer the WRT, the higher the DOC concentration is in inland waters. In other words, longer WRT and slower water velocity generally result in smaller DC flux in inland waters. More interestingly, the decreasing rate of DC flux in rivers is twice as much as that in lakes and reservoirs; thus, the magnitudes of riverine DOC and DIC fluxes are more sensitive to WRT than lakes and reservoirs. Besides, our analysis suggested that the DOC concentrations in inland waters are positively correlated with the WRT in the temperate zone because biotic production of carbon was greater than its consumption. In contrast, the concentration of DIC and CO2 in the temperate zone is negatively correlated with the WRT, respectively. In tropical and boreal regions, the DOC concentrations in inland waters are negatively correlated with the WRT because of high temperature- and rainfall-associated hydrologic dynamics in tropical regions and the widely distributed ice cover in the boreal regions. These findings have important implications for studying the global carbon cycle due to the significance of inland water in transporting carbon from land to ocean. Further study on the relationship between WRT and DC export in inland waters of the temperate zone is necessary, particularly for river systems.
Journal Article
European River Lamprey Lampetra fluviatilis (Petromyzontidae) of the Pskov Lakeland: Current State of Isolated Populations
Small freshwater (resident) populations of the European river lamprey Lampetra fluviatilis from an isolated from the sea upper part of a river system with numerous lakes (the upper reaches of tributaries of the Daugava River and Lake Peipus, Pskov Oblast, Russia) have been studied. Adult individuals of the lamprey have been attributed to common and large size groups; adults are similar to other resident lamprey from the Baltic Sea basin. The presence of larvae of different size and age groups indicates regular spawning of the European river lamprey in the studied watersheds. Analysis of the modern and historical (before the isolation) distribution of lamprey revealed a reduction in habitats and a decrease in the number of individuals. Dam-associated disruption of migration routes led to the disappearance of anadromous form, and consequently, disappearance of resident lamprey from most of the studied waterbodies. We attribute the decrease in the number of rivers inhabited by lamprey and abundance of the lamprey both to anthropogenic factors (direct blocking of an access of anadromous form of the lamprey to spawning grounds by hydraulic construction) and to the characteristics of the studied area. The richness of the river system with lentic waterbodies makes it suitable for lamprey inhabitation with an influx of large anadromous individuals capable of crossing such reservoirs in search of spawning sites.
Journal Article