Upstream Water Research Articles

Model Pengelolaan Waqaf dalam Keragamaan Etnis di Aceh

The purpose of this study is first, to explain the perceptions of the Gayo and Pesisir tribes towards waqf management. Second, it describes the waqf management model carried out by the Gayo tribe and the Aceh Coastal tribe in their respective regions. And third, providing ideas, concepts, and ideal practices in waqf management in Aceh. The research method used is the descriptive qualitative research method. The results showed that the majority of the people of Lhokseumawe City gave land waqf for places of worship and education, while the people of Central Aceh or the Gayo tribe had a tradition of using waqf for the common good of their ancestors, namely Livestock Locations (Peruweren), Uber-Uber and Blang Paku and ulu ni wih area (upstream water area). The waqf management model carried out by the Gayo tribe and the Aceh Coastal tribe in their area is still mostly carried out for religious purposes such as; the construction of places of worship (mosques, madrasahs, and study rooms or Islamic boarding schools), and most of them are used for public cemeteries and the people of Aceh, especially Central Aceh and Lhokseumawe, are also still taboo about waqf assets outside of immovable waqf such as cash waqf. Ideal management of waqf for districts/cities in Aceh that is capable of providing economic influence can be carried out with seven precise steps, namely Compilation of the Waqf Program; Empowerment of Waqf Assets; Waqf Assets Certification; Nazir Empowerment; Financial Reports and Management Systems; Government Integration; and Nazir Integration

SIMPLIFIED ADAPTIVE TRIANGULATION OF THE CONTACT BOUNDARIES OF THE DAM MODEL

To numerically solve the system of integral equations, it is customary to establish a discrete grid within each integration area. In the context of 3D modeling, these areas correspond to surfaces situated in space. The standard discretization technique employed for the computational domain is triangulation. This study addresses the integral equation system pertinent to the electrical tomography of dams. The structural model encompasses an embankment dam, the upstream and downstream water bodies, the dam's base, and a potential leakage region on the upstream side. An alternative configuration may be encountered in specific scenarios with no water downstream. Consequently, the model may incorporate up to nine distinct contact boundaries. Accordingly, the system of integral equations comprises an equivalent number of equations. Effectively resolving this system through numerical methods necessitates applying triangulation techniques to these diverse surfaces. While mathematical packages like Matlab offer triangulation functions, they may not fully address the specific demands of the problem. Additionally, the grid resolution should be heightened in proximity to key elements such as the sounding line, the supply electrode, and the various contact lines within the medium. These considerations transform the triangulation task into a distinct subtask within the numerical simulation of the resistivity tomography problem. In this paper, we provide our specific approach to this problem. The simplification of the triangulation algorithm is rooted in the predominant utilization of the two-dimensional geometric properties inherent to the object under study. For most contact boundaries, the triangulation is constructed layer by layer with a gradual modulation in triangle dimensions as one progresses from one layer to the next, orthogonal to the axis of the dam. Concerning the surface corresponding to the leakage area, cylindrical coordinates are used for surface parameterization. This approach enables partitioning the surface into discrete strata, facilitating a systematic, layer-by-layer grid construction. Additionally, points at the intersections of contact boundaries are integrated into the pre-existing triangulation by applying a standard function within the Matlab package. In the future, the mathematical modeling based on the Integral Equation Method with adaptive discretization will help incorporate real-time computations into information systems related to monitoring hydraulic structures.

Multi-objective optimization of diversion tunnel under the water conservancy project

Tunnel diversion is a method of diverting upstream water through a diversion tunnel where the river valley is narrow and not conducive to the placement of an open channel, and where the geological conditions of the riverbank hills are favourable for the excavation of a tunnel. The construction of a tunnel diversion is limited by topographical conditions, construction budget, and construction scale. Therefore, the choice of a reasonable solution for the construction of a tunnel diversion has a certain influence on the cost, efficiency, and risk of construction A comprehensive consideration of how to construct a tunnel diversion can achieve a multi-objective optimization to reduce costs and increase efficiency. This paper incorporates risk as a constraint, with the radius of the upper part of the tunnel half arch and the lower tunnel elevation as optimizable variables for optimization. Based on the analysis of actual hydropower project data, Matlab is used to derive the most optimizable solution considering different possible scenarios of water flow, and the obtained results, show that the comprehensive objectives of shorter construction time and lower cost can be effectively achieved by analyzing the variables under different scenarios where the risk is a constraint.

Assessment of surface water resource and allocation optimization for diverse demands in Ethiopia's upper Bilate Watershed

Water planning and management is very crucial for all computing sectors for water uses to maximize the scarce and allocated water uses based on their demands sustainably in Ethiopia's upper Bilate watershed. The shortage of surface water, especially during dry months, has become a major point of contention between upstream and downstream water users in the upper Bilate River. Therefore, the key objectives of the study are to evaluate the surface water resources and determine the best distribution for a range of requirements in the watershed. The historical climatic and stream flow daily data for the period of 2010–2019 have been used for the analysis. Hydrologic Engineering Center Hydrologic Modeling System-Geospatial Hydrologic Modeling Extension with the Hydrologic Engineering Center Hydrologic Modeling System was used for rainfall-runoff analysis. The model output further represents that the yearly overall surface water of the watershed is 502 MC M. Estimated annual environmental requirement is 75.32MCM which is 15% of the average annual available flow in watershed. Current annual irrigation, livestock, and domestic water demand were estimated to be 19.34 MC M, 12.39 MC M, and 79.4 MC M, respectively. The net amount of water delivered was 19.25 MC M, 79.28 MC M, and 12.36 MC M for irrigation, domestic, and Livestock demands, respectively, in the reference scenario. In the currently available (reference) scenario, 99.8% of the water supply need had been fulfilled, yet only 0.2% of the requirements for water were unmet. Average annual water demand of 111.13 MC M in the current scenario growth to 176.08 MC M when the future growth scenario. In contrast, for the future irrigation development and population projections scenario, 69.8% of the supply-demand became acquainted, and 30.2% of the demand for water remained unfulfilled in 2035. Therefore, to realize good water availability for productive use and allocate water optimal manner constructing a hydraulic structure (dam) upstream of the watershed was recommended.

Numerical investigation on entry of an inclined cylinder into water under uniform current and wind

The entry of a circular cylinder into water represents the problem of the coupling of multiphase flow with highly unsteady and nonlinear dynamics. Few studies have examined the influence of the initial angles of inclination of the object on the evolution of the cavity and the multiphase flow field under impact-induced loads in the presence of currents and wind. In this study, we develop a three-dimensional numerical model in OpenFOAM® to simulate and analyze this entire process. An overset mesh technique was used to reproduce the entire process of the entry of a circular cylinder into water as well as the formation, pinch-off, and collapse of the cavity. A comparison between our numerical results and previously published test data from the laboratory confirmed that the proposed numerical model can accurately simulate the dynamic characteristics of the multiphase flow field. The mode and time series of the closure of the cavity varied with the initial angles of inclination of the cylinder, and in turn influenced its translational and rotational characteristics of motion. The pressure, velocity and vortex structures suggest that the evolution and distribution of multiphase flow field for upstream and downstream water entry cases have varied characteristics.

Evolution Characteristics of Water Quality in Plain Reservoirs and Its Relationship with the Economic Development Response: A Case Study of Daheiting Reservoir in Northern China

In order to explore the evolution characteristics of TP and NH3-N in Daheiting reservoir since its construction, and their response to economic development, the monitoring data of water quality from 1992 to 2018 and statistical data of socio-economic development in Qianxi County were analyzed to examine the interannual evolution of TP and NH3-N and their correlation with upstream water quality, various economic indicators, and the scale of cage fish culture. The results show that, influenced by economic development, the evolution process of TP and NH3-N in Daheiting reservoir can be divided into three stages. In Stage I, the economic development of Qianxi County was slow, and the water quality of upstream water and the reservoir was good, with TP and NH3-N concentrations remaining relatively stable. In Stage II, Qianxi County entered a period of rapid economic development, and the TP and NH3-N in upstream water and Daheiting reservoir both increased significantly, with TP exceeding the standard limit. In Stage III, the intensity of external pollution control increased, and all cages were removed from the reservoir. Both TP and NH3-N showed a downward trend, but TP still exceeded the standard limit. Pearson correlation analysis and RDA analysis revealed that the levels of TP and NH3-N in Daheiting reservoir were mainly affected by the water quality of upstream water and the development of primary industry (including cage fish culture).

A momentum-based prediction model of backwater rise within and downstream of an emergent canopy in nonuniform flow

Vegetation is widely used to restore waterways and wetland ecosystems. However, emergent canopies create a nonuniform water surface, and predicting the backwater rise is necessary to evaluate the flood hazard. This paper investigates the water surface elevation from downstream to upstream of an emergent canopy in a steady nonuniform flow and predicts the upstream backwater rise. Laboratory flume experiments are conducted on rigid vegetation with varying coverage exposed to different flow rates. The backwater rise and the nonuniformity of vegetated flow are explored based on a momentum equation, and a general formula for backwater rise within and downstream of an emergent canopy is proposed for nonuniform flow. The results reveal that a unified phase diagram of backwater rise can be derived from the momentum model, which presents the variation of both the upstream and downstream water surface elevations and acquires a threshold to identify strong or weak nonuniformity in vegetated flow. The upstream water depth H1 exhibits a nonmonotonic variation, first decreasing and then increasing with water depth H2 at the trailing edge of the emergent canopy. Two partitions of subcritical flow and supercritical flow for the downstream water depth H3 are quantified by the experimental data. The proposed model can be used to accurately predict the backwater rise based on a dimensionless vegetated parameter Cveg and unit discharge q, as demonstrated by both the present and previous experimental results. This work improves the understanding and predictability of the nonuniformity and backwater rise generated by emergent canopies in natural or ecology-restored rivers.

Emergency intervention modes for ice jam events in large-scale water diversion projects

Abstract The formation of ice jams is sudden, and they will cause abnormal water level fluctuations in water diversion projects, affecting the water supply and even causing severe flood disasters. Based on the characteristics of the Middle Route of the South-to-North Water Diversion Project, this paper uses the numerical simulation method to establish an emergency intervention effect simulation model for ice jam events. The hydraulic response characteristics of the project under gate group scheduling and taking different emergency measures are analyzed with the water level deviation and stabilization time consumption of the pool as indicators. Moreover, this paper proposes an emergency intervention mode for ice jam events. The results show that using the gate group scheduling after ice jam events will cause a sharp rise in the upstream water level of the pool where the ice jams are located. Also, compared with other emergency measures, the electric heating ice melting measure has less influence on water level, and the de-icing effect is better. Finally, the emergency intervention mode can significantly reduce the maximum water level deviation and shorten the time required to stabilize the water level.

Critical examination of resilience and resistance in African American families: Adaptive capacities to navigate toxic oppressive upstream waters.

African American families navigate not only everyday stressors and adversities but also unique sociocultural stressors (e.g., "toxic upstream waters" like oppression). These adverse conditions are consequences of the historical vestiges of slavery and Jim Crow laws, often manifested as inequities in wealth, housing, wages, employment, access to healthcare, and quality education. Despite these challenges, African American families have developed resilience using strength-based adaptive coping strategies, to some extent, to filter these waters. To advance the field of resilience research, we focused on the following questions: (1) what constitutes positive responses to adversity?; (2) how is resilience defined conceptually and measured operationally?; (3) how has the field of resilience evolved?; (4) who defines what, when, and how responses are manifestations of resilience, instead of, for example, resistance? How can resistance, which at times leads to positive adaptations, be incorporated into the study of resilience?; and (5) are there case examples that demonstrate ways to address structural oppression and the pernicious effects of racism through system-level interventions, thereby changing environmental situations that sustain toxic waters requiring acts of resilience to survive and thrive? We end by exploring how a re-conceptualization of resilience requires a paradigm shift and new methodological approaches to understand ways in which preventive interventions move beyond focusing on families' capacity to navigate oppression and target systems and structures that maintain these toxic waters.

Origin, distribution and spatial characteristics of dissolved organic matter in the Heilongjiang River

The Heilongjiang River Basin is a vast area with significant DOM sources and composition differences. The mechanism of DOM degradation under spatial variation remains unclear. This research investigated the degradation characteristics of DOM in different watersheds of the Heilongjiang River. DOM levels were higher in midstream waters, while DOM degradation rates were higher in midstream and downstream waters. The parallel factor analysis (PARAFAC) results showed that the upstream amino acid fraction was significantly depleted, the midstream was dominated by the degradation of DOM of terrestrial origin, and the downstream humic acid fraction was decreased considerably. Gene sequencing results indicated that the upstream, middle, and downstream water bodies' microbial community composition and structure differed significantly. The network analysis results revealed microorganisms in upstream water bodies mainly utilized amino acid-like substances and small molecule humic acids. Microorganisms in the middle and lower reaches of the water column were characterized by the utilization of humic acid-like fractions. In this study, we further screened the key driving microorganisms (e.g., Flavobacterium and Lacibacter) responsible for the difference in the DOM utilization function of upstream-to-midstream and midstream-to-downstream microorganisms in the Heilongjiang River. These findings will help identify the cycling process of DOM under spatial variation and predict the succession pattern of microbial communities.

Synergistic management of forest and reservoir infrastructure improves multistakeholders’ benefits across the forest-water-energy-food nexus

Forest management can influence multistakeholders' benefits across the forest-water-energy-food nexus at the watershed scale. However, bringing synergistic gains for multiple stakeholders is still a challenge for regional sustainable management. We took the Changhuajiang basin in China's Hainan Island as a case to present the impacts of synergistic management for upstream forest and reservoir optimization on the benefits of downstream hydropower enterprise and different farmers. By multimodel ensembles and scenario analysis, we quantified the relationships among upstream forest ecosystem management (rubber-intercropped), reservoir, water flow and downstream stakeholders' benefits (i.e., hydropower generation for the energy company, and available irrigation water for two downstream sites' farmers). We also adopted the genetic optimization algorithm to obtain the optimal reservoir infrastructure operation rule for the benefit improvement of multiple stakeholders. We found that rubber-intercropped management significantly increased reservoir inflow in the dry seasons (5%–170%) and reduced it in the rainy seasons (0.5%–7%). The irrigation water availability for downstream farmers in the Gao Canal and downstream irrigation areas correspondingly increased by 7% and 24.3% on average, respectively, with a slight change in hydropower production. Further, we found that water regulation by reservoir optimization operation could enhance the irrigation water supply (36.6–92% and 0–100% in Gao Canal and downstream irrigation areas, respectively) and hydropower generation (14.8–28.4%). This study indicates that the effect of upstream forest management on downstream multistakeholders' benefits could be strengthened by reservoir water flow regulation across the forest-water-energy-food nexus, and demonstrates the key role of infrastructure in regulating ecosystem service flow for strengthening the benefits of multistakeholders in the context of ecosystem management.

Effect of intense rainfall and high riverine water level on compound flood hazards in a river-valley city: A case study of Yingde, China

River-valley cities are susceptible to compound floods induced by intense rainfall and high riverine water level, especially where design standard of levees is low and overtopping-induced fluvial flood are very likely to run into urban area. However, the holistic impact of high riverine water level and intense rainfall on a river-valley city still needs to be assessed within a quantitative analyzing framework. In this study, a typical river-valley city named Yingde in Guangdong Province of China is selected as the study area. A framework combining multivariate statistical analysis and numerical hydrodynamic modeling is proposed to quantitatively assess the compound flood hazard in river valley cities. To be specific, a compound flood numerical model that can integrate rainfall and overtopping flow processes is first developed and validated based on historical observations. Then, the joint probability distribution of rainfall and riverine water level is established based on the copula function. After that, the compound flood scenarios corresponding to different joint return periods are simulated and compared. Considering only one factor may underestimate the probability of flooding occurrence. The compound flood severity in terms of both inundation area and depth for the study area is majorly dominated by intense rainfall, but the extra contribution from upstream water level cannot be ignored. An inundation amplification factor can be used to assess the amplification effect of high upstream water level on the flood hazard of the riparian area. For a site that is quite near the river, the inundation amplification factor can be drastically decreased as the levee crest elevation is heightened. Without the contribution from the fluvial floods, the rainfall-induced inundation could be several times smaller than the compound floods.

Microbiology and Physicochemical Characteristics of Surface Water from a Local Refinery Site in Port Harcourt, Nigeria

Water plays a vital role in maintaining human health but due to an increase in industrialization, urbanization and other anthropogenic activities, surface water pollution is on an increase. This research was carried out to investigate the microbiological and physicochemical status of a crude oil polluted surface water in Iwofe River, Rumuolemini, Port Harcourt. Samples were collected from two points (Upstream and Downstream) bi-monthly for a period of three months. The THB counts for the upstream and downstream samples were 1.7 × 108cfu/ml and 1.4 × 108 cfu/ml, respectively while the THF counts for the samples were 3.0 × 106cfu/ml and 1.4 × 106 cfu/ml, respectively. Hydrocarbon utilizing bacterial (HUB) counts were higher in the upstream (1.5 × 106cfu/ml) than downstream (4.3 ×105cfu/ml) location of the Iwofe River. The Hydrocarbon utilizing fungal (HUF) count ranged from 1.0 × 105cfu/ml to 1.4 × 105 cfu/ml in the upstream and downstream water samples, respectively. The results of all the microbiological parameters analyzed indicated that the total heterotrophic bacterial (THB) and Total heterotrophic fungal (THF) counts were higher in the upstream than in the downstream location. The Most Probable Number (MPN) method used for the determination of coliform counts revealed the presence of coliforms both upstream and downstream, with an MPN index of 1,600/100ml of each sample. Some of the bacterial species isolated were Staphylococcus aureus, Escherichia coli and Vibrio cholerae while the fungal isolates included Aspergillus fumigatus, Penicillium species and Alternaria species. The high level of oil contamination poses a great health threat and there is a need for remediation of the aquatic ecosystem.

Improving the power output estimation for a tidal power plant: a case study

The aim of this study is to analyse the importance of considering the variation in the discharge coefficient (Cd) of a sluice passage and the tidal current speed (i.e. the flow speed approaching the passage) in improving the estimation of power output for a tidal power plant. The simulation results, using a commercial computational fluid dynamics software package, Flow 3D, have shown that the Cd value of a sluice passage varies with the upstream (i.e. on the sea side of the impounded area) water level. In addition, the results of a case study carried out in the Taedong bay (Democratic People's Republic of Korea), using a zero-dimensional model, highlight the importance of considering variations in the tidal current speed as well as Cd when estimating the power output for a tidal power plant. In this study, a detailed scheme is proposed to consider the approach speed at each stage of filling, holding, generating and holding for the mode of ebb generation. It is hoped that the results of this study will help scientists, engineers and decision makers to accurately evaluate the tidal power output of tidal barrages and lagoons in many regions of the world.

Spatiotemporal variations and risk characteristics of potential non-point source pollution driven by LUCC in the Loess Plateau Region, China

With increasing human activities, regional substrate conditions have undergone significant changes. These changes have resulted in temporal and spatial variations of non-point source pollution sources, which has a significant impact on the quality of the regional soil, surface water, and groundwater environments. This study focused on the human-disturbed Loess Plateau region and used an enhanced potential non-point-source pollution index (PNPI) model to explore the dynamic changes of regional potential non-point-source pollution (PNP) and the associated risk due to land use and land cover change (LUCC) over the past 31 years. The Loess Plateau region is mainly composed of cultivated land, grassland and forest, which together account for 93.5% of the watershed area. From 1990 to 2020, extensive soil and water conservation measures were implemented throughout the Loess Plateau region, resulting in a significant reduction in the non-point source pollution risk. Using the quantile classification method, the study area’s PNP risk values were categorized into five distinct levels. The results revealed a polarization phenomenon of PNP risk in the region, with an increase in non-point source pollution risk in the human-influenced areas and a rapid expansion of the very high-risk area. However, the non-point source pollution risk in the upstream water source area of the watershed reduced over the study period. In recent years, the rapid urbanization of the Loess Plateau region has been the primary reason for the rapid expansion of the very high PNP risk area throughout the watershed. This study highlights the significant impact of LUCC on the dynamic changes in PNP risk within the Loess Plateau region, providing crucial insights into future conservation and urban planning policies aimed at enhancing the ecological health and environmental quality of the region.

An evolutionary-based polynomial regression modeling approach to predicting discharge flow rate under sheet piles

The discharge flow rate beneath sheet plies is an essential parameter in designing these water retaining structures. This paper presents a unified framework for modeling and predicting discharge flow rate using an evolutionary-based polynomial regression technique. EPR (Evolutionary Polynomial Regression) is a data-driven method based on evolutionary computing to search for polynomial structures representing a system. The input parameters in the modeling procedure included the sheet pile height, upstream water head, and the hydraulic conductivity anisotropy ratio. Due to ever-increasing demand for water, a widely held view on predicting and controlling the available water behind reservoirs, dams, barrages, and weirs is of vital importance. To this end, the sheer novelty of the current study has been worn off through the development of a comprehensive model to predict the flow rate considering the most effective variables in the seepage issue. To the best of our knowledge, the research conducted in the literature has yet to cover the whole seepage problem using a comprehensive database extracted by numerical methods; thus, a comprehensive finite-element-based artificial database including 1000 data lines was created using the Scaled Boundary Finite Element Method (SBFEM) by simulating seepage beneath sheet plies covering a considerably wide range of seepage-related real-world values. The database was then employed to develop and validate the EPR flow rate prediction model. Data were divided into training (used for creating the models) and testing (for validating the developed models) data based on a statistical process. The procedure for preparing the data and developing and validating the models is presented in detail in this paper. The main advantage of the proposed models over a conventional and neural network and most GP (Genetic Programming)-based constitutive models is that they provide the optimum structure for the material constitutive model representation as well as its parameters, directly from raw experimental (or field) data. EPR can learn nonlinear and complex material behavior without any prior assumptions on the constitutive relationships. The proposed algorithm captures and transparently presents relationships between contributing parameters in polynomial expressions providing the user with a clear insight into the problem. EPR-based model predictions demonstrated an excellent agreement with the unseen simulated data used for validating the developed model. A parametric study on the presented models was conducted to investigate the effects of the contributing parameters on model predictions and the consistency of the parameter relationships with the database. Results of the parametric study showed that the effects of variations in the contributing parameters on EPR predictions are in line with the expected behavior. The merits and advantages of the proposed technique are discussed in the paper.

Formation conditions of wave-type flows at stilling basins with a drop

The formation conditions of maximum- and minimum-wave jumps were experimentally investigated. A total of 110 wave-type jump experiments were carried out for several discharges, supercritical upstream and subcritical downstream water depths and drop heights. The experimental results revealed that the influential parameters on wave-type jumps are the upstream Froude number and the relative drop height. As the classical hydraulic jump equation is not sufficient to define conjugate depths of wave-type flow, empirical equations were developed for defining the conjugate depths of maximum-wave jumps and minimum-wave jumps (for which insufficient experimental data are available in the literature). The agreement between calculated and measured conjugate depths was good. It was also found that the value of the lower limit for the upstream Froude number is not constant for the formation of a maximum-wave jump – it depends on the relative drop height. Furthermore, the experimental results showed that the energy-dissipation ratios of maximum- and minimum-wave jumps are equal to or larger than those of classical hydraulic jumps. For this reason, wave-type jumps may be preferred at stilling basins with drops along with A-jumps.

Assemblage Patterns of Microalgae along the Upstream to Downstream Gradient of the Okavango Delta: Abundance, Taxonomic Diversity, and Functional Diversity

This study addresses the gap in understanding the diversity, species, and functional trait distribution of different algal groups that occur in the Okavango Delta (a near-pristine subtropical wetland in northwestern Botswana) across hydrological and habitat gradients. We systematically characterize the delta’s algal flora, addressing the gap left by previous research that was limited to single algal groups (e.g., diatoms) and/or only looking at upstream areas in the Okavango River basin. We analyzed 130 algal samples from 49 upstream and downstream sites with higher and lower flooding frequency, respectively, across a river-to-floodplain habitat gradient. Chlorophyta and Bacillariophyta dominated both abundance and taxon richness (>80%) of the total 494 taxa found from 49,158 algal units counted (cells, colonies, coenobia, and filaments). Smaller algae were more abundant in downstream floodplains than in upstream channels and lagoons. Motile and siliceous algae were much more abundant than non-motile, nitrogen fixing, and phagotrophic algae. The frequency of these traits was associated more with flooding frequency than habitat type. The highest algal richness and diversity were found downstream, where shallow floodplain ecosystems with seasonally fluctuating water depths offer greater habitat heterogeneity, and macronutrients are resuspended. The increasing threats from upstream water abstraction plans, fracking, and climate change require enhanced protection and monitoring of the Okavango Delta’s natural annual flood-pulse to maintain the high species and functional diversity of this unique wetland’s microalgae.

Distribution of microplastics in upstream and downstream surface waters of the Iranian rivers discharging to the southern Caspian Sea.

Microplastic pollution in the riverine ecosystems has caught many attentions in the scientific literatures. However, little information is available about the abundance and distribution of microplastics of the rivers discharging to the Caspian Sea. The aim of this study was to assess the spatial and seasonal distribution of microplastics in the surface waters of thirteen rivers discharging to the southern Caspian Sea. Microplastics were found in all stations with uneven distributions. The average concentrations of microplastics in the stations during snowmelt and dry seasons were 1.406 ± 0.1380 microplastics/m3 and 0.4070 ± 0.01500 microplastics/m3, respectively. Positive gradients of the rivers microplastics concentration from upstream to downstream were found. White/transparent polyethylene (PE) particles with the shape of fragment/film and the length (L) of ≤ 1mm were the most common microplastics in the surface waters of the rivers discharging to the southern Caspian Sea. Also, the mean concentration of microplastics in spring snowmelt and runoff period was 3.45 times higher than in dry period. Factors such as sewage and household wastes; landfills; and recreational-tourism, fishing and agricultural activities along the rivers may contribute to microplastic contamination in downstream stations. Our data provide baseline information of microplastics in surface waters of rivers discharging to the southern Caspian Sea.

Research and Application of the Calculation Method of River Roughness Coefficient with Vegetation

The roughness coefficient is a comprehensive parameter reflecting river resistance, which is widely used in the planning and design of river regulation and flood control projects. In recent years, as the upstream water conservancy and hydro-power projects have been put into operation, the frequency of low flow in the middle and lower reaches has increased, and the frequency of flood flow has decreased. All kinds of vegetation in the river floodplain grow luxuriantly, which causes a change in the river resistance and roughness coefficient. The present study was carried out with theoretical analysis and laboratory tests. A formula for the roughness coefficient calculation was derived based on the momentum equilibrium equation and momentum exchange between the vegetation layer and upper layer. The relationship between the depth-averaged velocity within the vegetation layer and depth-averaged velocity of the whole flow was analyzed. The reliability of the formula was verified by a large amount of previous experimental data. Based on the derived formula, the variation law of the roughness coefficient with vegetation density, vegetation height, and water depth were obtained. For the emerged vegetation flow, the Manning coefficient tended to increase with the increase in the vegetation density and water depth. For the submerged vegetation flow, the Manning coefficient showed a trend of decreasing with the increase in the water depth and increased with the increase in the vegetation height. Finally, the derived formula was applied in the Yueyang reach of the Yangtze River and the Duliujian River. The study can be applied in the fields of water level-flow discharge relationship analysis and the water surface line calculation of vegetated rivers.