Journal of Hydro-environment Research最新文献

Accurate streamflow forecasting is very useful in water resources management, design of hydraulic structures, and almost all issues related to the use of water and water resources, especially in arid regions that have increased in recent years. Since water is the source of all life and the most important basic element for humanity to continue its life, streamflow prediction studies increase its importance daily. This research combined the boosted tree (BT) model with robust empirical mode decomposition, empirical mode decomposition, complete ensemble empirical mode decomposition with adaptive noise, empirical wavelet transforms and variational mode decomposition for predicting daily average streamflow data. While historical streamflow data was input in the model's setup, one-day lead-time streamflow data was used as the target. 70% of the data is reserved for training and the rest for testing. 5-fold cross-validation technique was used to solve the over-fitting problem. The coefficient of determination, mean squared error, Nash-Sutcliffe efficiency and percent bias statistical criteria and Taylor diagrams, polar plot, scattering diagram, and violin plot were used to determine the algorithm's success. At the end of the study, it was found that the most successful streamflow predictions were made with the variational mode decomposition-based BT hybrid approach.

Research on water flow resistance characteristics in a vegetation environment is a hotspot in environmental fluid research, which is primarily concentrated on the calculation of the vegetation drag coefficient C_d. At present, relatively few studies exist on the resistance characteristics of vegetation under non-uniform flow conditions, resulting in few general expressions for the research of C_d for this type of condition. In response to these scientific problems, this study selects shrub vegetation as the research object and generalised it as cylinders for the simulation study. This study adopts quadratic and Gaussian functions to change the coordinate expression of cylindrical vegetation C_d and then proposes the drag formulas of cylindrical vegetation in non-uniform flow for non-rainfall and heavy rainfall conditions based on regression analysis. Finally, this study substitutes the proposed C_d formula into the Saint-Venant equation to calculate the depth of channel flow. The newly proposed equations are verified by comparing the measured flow depth data with the calculation results. This study provides technical support for refined hydrodynamic simulations of vegetated flow regions.

Fluvial floods are commonly studied as an occurrence at the level of a specific basin and are speculated to be closely related to the basin's morphometry. It is possible to identify and rank sub-basins based on how susceptible they are to fluvial flooding events using morphometric criteria. However, one of the key causes that triggers fluvial flooding is the increase in precipitation extremes and changes to their patterns. In this study, influence of morphometric factors and extreme precipitation events on the hydrological responses of the Brahmani River, India as well as their sensitivity to fluvial flooding, are investigated to identify the most vulnerable sub-basin in a catchment. The morphometric parameters were calculated from a digital elevation model (DEM), and the change in trend of extreme precipitation indices was detected using precipitation data of period 1991 to 2021. Furthermore, the Standardized Precipitation Index (SPI) was used to determine the frequency of wet cycles on time scale of 1, 3, 12, and 24 months, as well as their link to fluvial flooding. The two sub-basins of the catchment that are most vulnerable to river flooding are recognised as Noamundi and Gomlai based on morphometric criteria. However, analysis of SPI and extreme precipitation indices showed that the Jenapur sub-basin is the most vulnerable to flooding. It is also corroborated with analytic hierarchy process (AHP) based weighted overlay analysis and historical flood records. The outcomes will assist researchers in better understanding the mechanisms causing flooding in the Brahamni River Basin and in developing flood mitigation practices for the most vulnerable Jenapur sub-basin.

Broadcasted fertilization for the reproduction of invertebrates is accomplished through a complicated interaction between spawned gametes and the surrounding flows. Most gametes encounter each other in the vicinity of the sea urchin body where unique flow structures develop, and so analysis of local flow characteristics allows us to better understand the effect of flow on the fertilization process. This study applied a Lagrangian framework based on computational fluid dynamics to estimate the fertilization rate of eggs in a range of flow velocities (0.025–0.2 m/s) and the fertilization rate was the highest at U = 0.1 m/s, which is an intermediate flow speed. Among the four classified sub-zones, such as the aboral surface, wake, substrate, and water column, fertilization occurred most frequently in the wake and substrate regions. The relationship between fertilization rate and flow structures was investigated using three parameters: 1) standardized Morisita index to quantify the pattern of gamete distribution, 2) length of the recirculation zone to specify the areas where the eggs are most frequently fertilized, and 3) integral scale to estimate the dimension of vortex structures downstream. The results of this study show that the fertilization rate is higher inside the recirculation zone, especially when strong vortex structures are observed because the flow provides a favorable condition for the gametes to aggregate and collide with each other.

Limited research has been conducted on transverse energy loss in meandering channels. Previous studies made assumptions regarding a linear vertical profile of transverse velocity and rectangular cross sections with horizontal transverse beds, neglecting the effects of nonlinear transverse velocity profiles and transverse bed slopes that contribute to topographic steering. In this study, a novel expression for the transverse energy loss slope is derived analytically. This expression incorporates a nonlinear vertical distribution for transverse velocity and considers non-rectangular cross sections, thereby improving the computation of roughness coefficients in curved channels. A topographic steering number is introduced, which indicates the presence of topographic steering when it exceeds unity. The developed equation rectifies the previous underestimation of sinuosity in natural rivers when compared to existing equations. Additionally, an expression for superelevation is derived, accounting for channel roughness and transverse bed slope, unlike previous equations. The study reveals that roughness can significantly affect the height difference between outer and inner banks. Under higher roughness conditions, the height difference can exceed predictions from existing formulas by up to 50%. This emphasizes the importance of considering roughness effects in accurately estimating superelevation. The developed equations are validated through comparisons with available field, laboratory, and numerical data.

Extremely high lead level in tap water caused by particulates has attracted increasing attention in recent years. Despite extensive research on the role of particulate Pb in water supply systems with lead service lines, little information is available on the role of particulate Pb in copper (Cu) water distribution systems. In this study, the dissolved, colloidal, and particulate lead and copper concentrations in representative prototype copper pipe water distribution systems with leaded solder joints and brass fixtures are measured. The effects of flow rate and stagnation time on metal fractionation are investigated. For each experimental scenario, all the water that stagnated inside the system is sampled to have a comprehensive understanding of lead contamination. Sampled at flow rates of 200–250 mL/s, the soluble lead and copper make up 60–96 % of the total concentration in the samples after hours of stagnation. More than half of the Pb and Cu particles are larger than 0.8 μm. Higher flow rates result in substantial increases in particulate metal concentrations but have no apparent effect on dissolved metals. The soluble and particulate copper concentrations ($\sim$ 100–250 μg/L) both increase with stagnation time. For the case of Pb, while the particulate concentration increases (up to $\sim$ 40 μg/L after 12 h), the soluble concentration does not change significantly beyond 4 h; this can be attributed to the different solubilities of Pb ($\sim$ 20 μg/L) and Cu ($\sim$ 200 μg/L) in tap water. The results also show that particulates suspended by clean “once through” water (without prior stagnation) can lead to high levels of Pb contamination ($>$ 10 μg/L).

River Thamirabarani sub-basin lies in the southern part of the Western Ghats in the Kanyakumari district of Tamil Nadu, India. The basin’s landforms are formed by swift surficial characteristics with undulated terrains composed of steep-sloped valleys, valley fills, and short-length streams with intensive flows that makes-up site-specific hydro-morphological characteristics. In this study, the GIS-based Natural Resource Conservation Service-Curve Number (NRCS-CN) model is used to assess rainfall-induced runoff by analyzing various hydrological parameters. The curve number (CN) is assigned to each hydrologic soil group (HSGs) based on the measurement of initial abstraction (Ia) and potential maximum retention (S) derived from soils, landuse/ land cover, antecedent soil moisture, etc. The resulting map shows the estimated runoff at the rate of 2.27 – 5.94 mm/m²/yr for the whole study area, whereas the higher runoff rate (4.83 – 5.94 mm/m²/yr) is noted in the upland range of the swift surficial terrains in the north and north-eastern parts that encompasses undulated structural hills, steep-sloped valleys, inselberg, and denudational hills, etc., whereas the work of swift surficial terrains and associated slope gradient of the landforms are considered to be higher runoff rate than the other parts. The moderate runoff rate (2.92 – 3.98 mm/m²/yr) is estimated in the middle parts of pediplains that consist of croplands, plantations, riverbanks, fallows, and built-up areas. Significantly, the lower runoff rate (<2.92 mm/m²/yr) sparsely occurred in the different landforms of the middle and southern parts that include pediplains, riverbanks, natural vegetative covers, valley-filled sediment deposits, etc. Overall results indicate that the higher runoff found over the swift surficial landforms in the north and north-eastern parts due to intensive flow through short-length stream orders. This study is mainly used for understanding hydro-morphological processes and their impacts on basin environments.

River restoration projects often make use of grade-control structures in order to prevent channel degradation, improve their ecological resources, and regulate floods. The time evolution of localized scour that can occur downstream of grade-control structures represents a crucial component in the design of those projects. This is because erosion processes may undermine the stability of hydraulic structures and compromise their effectiveness. Although localized scour has been widely investigated (mostly via laboratory models), there is significant scatter in results produced by the large number of obtained empirical equations. Consequently, there is a need for more general tools based on theoretical approaches that might overcome the limits of ad-hoc, experimental methods. In particular, a model based on the application of the Phenomenological Theory of Turbulence (PTT) has been recently developed by the last three authors to predict scour-depth evolution under steady flows. Nevertheless, in practical applications, scour phenomena usually occur during floods characterized by variable flow discharges. In this paper, for the first time to the authors’ knowledge, a detailed analysis of the basic assumptions of the PTT-evolution model allowed us to assess their validity for scour processes at different grade-control structures under unsteady (time-dependent) flows. By re-analyzing the dynamics of the scour evolution under unsteady flow conditions, we corroborate its consistency with the steady counterpart and with jet-driven scour problems, evincing that a homothetical evolution of the scour hole occurs during the developed phase. Finally, we provide a confirmation of the general validity of the theoretical approach presented herein. We show that it can be successfully applied to a large range of structure configurations and hydraulic conditions, without any significant modification. This last result is particularly important, since it paves the way to a unique, first-principles-based tool that can be helpful to design hydraulic structures.

In this research, the flow features around a spur dike located in a 90˚ sharp channel bend have been studied experimentally in detail. Results showed that the effects of the spur dike on upstream sections increased by increasing α (spur dike location from the beginning of the bend). In addition, by increasing α, the horseshoe vortex (C3) and secondary flow in the channel bend (C1) strengthened. The energy and the Reynolds shear stress in the C3 region decreased by increasing α. It is recommended to use a Barycenteric Map (BM) instead of the normal Reynolds stresses to find the anisotropy nature accurately. A strong anisotropic condition was detected at the border of the recirculation flow region and the main flow. However, in the C3 and the interaction regions, the isotropy condition improved. In the main flow region, by increasing α, the isotropy degree improved. However, by increasing α, an increase in the development of the region with a high anisotropy degree towards the recirculation region was observed. The anisotropy degree in the near-bed layer region and the shear layer region is comparable. However, the anisotropy nature is different. The maximum error of the numerical simulation based on isotropic turbulence occurred at the shear layer region where the severe cigar-shaped turbulence occurred.

A long-term perspective of climate change patterns leads to the strategic management of limited water resources and consequently achieves the maximum level of social satisfaction between the various sectors in a water allocation system. Therefore, this study first adopts Soil &Water Assessment Tool (SWAT) to simulate future climate change patterns [2020–2050 and 2051–2080] under Representative Concentration Pathway (RCPs) scenarios, and then the extracted SWAT output is applied as the initial data in a bi-level programming model in which the manager of the upper level (MUL) tries to maximize the level of social satisfaction between sub-areas while the lower level manager (MLL) focuses on maximization of multi-sectoral social satisfaction. Also, historical data collected from Zayandehrud basin, Iran as a case study are considered for calibration, validation, and subsequently projecting the runoff data for mentioned periods. Based on the output related to the regional hydrological cycle under the [RCP4.5/2020–2080 & RCP8.5/2020–2080] scenarios, the study area is strongly affected by drought and relative temperature increase. Accordingly, due to the shrinkage of water resources in the basin, the highest degree of consumer satisfaction is related to the domestic sector as the smallest recipient of water resources. Thus, with the development of adaptation measures such as the use of demand reduction leverage for the effective use of limited water resources, the challenge of demand dissatisfaction for both the industrial and agricultural sectors is significantly improved.