River Flow Characteristics Research Articles

Design Guideline for Hydropower Plants Using One or Multiple Archimedes Screws

The Archimedes/Archimedean screw generator (ASG) is a fish-friendly hydropower technology that could operate under a wide range of flow heads and flow rates and generate power from almost any flow, even wastewater. The simplicity and low maintenance requirements and costs make ASGs suitable even for remote or developing areas. However, there are no general and easy-to-use guidelines for designing Archimedes screw power plants. Therefore, this study addresses this important concern by offering a simple method for quick rough estimations of the number and geometry of Archimedes screws in considering the installation site properties, river flow characteristics, and technical considerations. Moreover, it updates the newest analytical method of designing ASGs by introducing an easier graphical approach that not only covers standard designs but also simplifies custom designs. Besides, a list of currently installed and operating industrial multi-Archimedes screw hydropower plants are provided to review and explore the common design properties between different manufacturers. On top of that, this study helps to improve one of the biggest burdens of small projects, the unscalable initial investigation costs, by enabling everyone to evaluate the possibilities of a green and renewable Archimedes screw hydropower generation where a flow is available.

Transverse distribution of the streamwise velocity for the open-channel flow with floating vegetated islands.

Floating vegetation islands (FVIs) have been widely utilized in various river ecological restoration projects due to their ability to purify pollutants. FVIs float at the surface of shallow pools with their roots unanchored in the sediment. Biofilm formed by roots under islands filters nutrients and particles in the water flowing through it. Flow field disturbance will occur, and transverse distribution of flow velocity will change due to the existence of FVIs. Transport efficiency of suspended solids, nutrients, and pollutants will also be altered. A modified analytical model that considers the effects of boundary friction, drag force of vegetation, transverse shear turbulence, and secondary flow is established to model the transverse distributions of depth-averaged streamwise velocity for the open-channel flow with FVIs using the Shiono and Knight Method. The simulation results with suitable boundary conditions successfully modeled the lateral profile of the depth-averaged streamwise velocity compared with the experimental results of symmetrical and unsymmetrical arrangements of FVIs. Hence, the presented model is of guiding significance to investigate the flow characteristics of rivers with FVIs.

Boundary Influence and Flow Characteristics of Orisa and Ala Rivers in Kwara and Ondo States, Nigeria

In this study, the effects of boundary influence on flow characteristics of Rivers Ala and Orisa were investigated. Soil samples were collected from three points each from both rivers namely Glory Parish Area (GPA), Olusola Oke Area (OOA) and Fiwasaye; Aran-Orin Area (AOA), Rore and Omu-Aran on Rivers Ala and Orisa Respectively. A MGG/KL-DCB Portable Electromagnetic Velocity Meter was used to measure the in-situ readings of discharge and velocity at the various points. The sediments collected from the sampling points were placed in the Flume in the Hydraulic Laboratory of Civil Engineering Department, Landmark University. The Flume was then set with the measured parameter (Discharge) for each sampling point to apply the Flume to determine the Velocity for both Rivers at slopes of 0.008 to 0.056 respectively. The velocities obtained at the different slopes were inserted into Manning’s Coefficient equation to obtain the flow characteristics. The relationship between the velocity and Manning’s Coefficient was determined using the Spearman’s rank correlation coefficient. All analyses were done at P-value less than 0.05 level of significance. The velocity varied between 0.0237± 0.0004 and 0.0587± 0.0004 m/s; 0.0542± 0.0004 and 0.0701± 0.0003m/s and 0.0789± 0.0005 and 0.0172± 0.1323m/s for GPA, OOA and Fiwasaye for Ala River and between 0.0751± 0.0007 and 0.1008± 0.0006m/s; 0.0628± 0.0007 and 0.0839± 0.0004m/s and 0.0421± 0.0005 and 0.1076± 0.0004m/s for AOA, Rore and Omu-Aran for Orisa River. The results of the effects of soil boundary influence showed that the velocity was inversely proportional with the Mannings’ coefficient at all sampling points of both rivers if the geometry of the river channel is kept constant. This indicates that areas with high velocities are prone to flooding. Further studies should be carried out on more sampling points on the rivers to confirm flow characteristics of the rivers.

Study on river health assessment based on a fuzzy matter-element extension model

In order to facilitate watershed management, we developed an expansive river health assessment method based on a fuzzy matter-element extension model in this study that developed based on the transitive hierarchies and degree of membership from improved fuzzy optimization theory. Eight characteristics of river flow, namely, the morphology, flow, water quality, river habitat, aquatic organisms, riparian zone, flood control safety, and level of the water supply, were investigated in this study to establish a system of indices to assess river health. We apply the above method to a river health assessment in the Luanhe River as sub-healthy. The results show that the method is accurate for the river health assessment compared with the actual conditions in Luanhe river. Moreover, the river health assessment method described in this study covers the different health states of river ecosystems, including the natural function and the social service function of a river. It is a reasonable river health assessment method that can evaluate river health status systematically, comprehensively and accurately. Therefore, this method is reasonable and effective and can be used to assess the ecological health of rivers in other regions.

ИССЛЕДОВАНИЕ ОСНОВНЫХ ХАРАКТЕРИСТИК И ВНУТРИГОДОВОГО РАСПРЕДЕЛЕНИЯ СТОКА ВОДЫ РЕК ТЕРРИТОРИИ Г. АЛМАТЫ

The article is devoted to the study of the flow of the rivers of the metropolis of Almaty. Small rivers of Almaty attract more and more attention every year, as their water resources are widely used for household and drinking needs, irrigation, energy, and for other purposes. The health and well-being of the population depends on their water content. The article analyzes in detail the conditions for the formation of the water flow of rivers crossing the urbanized territory of Almaty, climatic characteristics affecting the flow. The description of the methodology and the results of calculating the characteristics of the average annual water flow and intra-annual flow distribution are given. Changes in the characteristics of river flow caused by climatic factors of recent decades are estimated.

Modeling biogeochemical processes in the Azov Sea using statistically processed data on river flow

Introduction. This work is aimed at solving the problem of phytoplankton dynamics in the coastal environments using the example of the Azov Sea. This takes into account the transformation of forms of phosphorus, nitrogen and silicon, as well as the aquatic medium motion, the distribution of temperatures and salinities over the sea area. River flow, varying in volume and chemical composition, affects significantly the variability of hydrophysical and biogeochemical parameters of the processes occurring in the coastal environment. This explains the need for statistical processing of the data from long-term observations over the river flow characteristics. Materials and Methods. The mathematical model of biogeochemical cycles is based on a system of non-stationary equations of the convection-diffusion-reaction of parabolic type with nonlinear functions of sources and lower-order derivatives, to which the corresponding initial and boundary conditions are added. In the course of statistical analysis of the series of long-term observations over river flows, the values of the following indicators were found: skewness coefficient, degree of kurtosis, variance and standard deviation, coefficient of variation, autocorrelation coefficient, Neumann ratio, and Anderson criterion. Results. The statistical analysis of the series of long-term observations over the hydrochemical indicators of the Don river suggests heterogeneity of the field data. This is due to the stochasticity of nutrient inputs and the volume of freshwater flow to the sea as a result of natural and anthropogenic factors. Field data should be correlated with seasonal changes in the aquatic environment temperature. This paper presents the results of a computational experiment to model the dynamics of phytoplankton populations in summer season, when temperatures are favorable for their reproduction and growth. The proposed mathematical model considers the spatially inhomogeneous distribution and transformation of forms of phosphorus, nitrogen, and silicon, as well as changes in salinity, temperature, and motion of the aquatic environment. Discussion and Conclusions. The multispecies mathematical model of the dynamics of phytoplankton populations is considered with account for the transformation of forms of phosphorus, nitrogen, and silicon in the coastal environments. The analysis of data from field observations, for which its major statistical parameters are calculated, is carried out. As a result, it is concluded that data of the long-term observations are significantly variable. This is due to two reasons. Random nature of the input of nutrients and the volume of river flow as a result of anthropogenic factors is the first reason. The second reason includes the alternation of relatively high-water and low-water periods for fresh flow over the last 12-15 years. The hydrological regime is changing mainly due to the reduction of the average annual freshwater flow of the Don and partly of the Kuban. This trend is likely to increase due to climate changes, as well as with further regulation of the Don river flow after the Bagaevsky hydroelectric installation start-up. Numerical experiments based on the field data confirmed the predictive validity of the developed models and programs. They can be used to predict change in the composition and abundance (concentrations) in the Azov sea core planktonic populations, which define, on the one hand, food resources, and, on the other hand, the aquatic environment in terms of the ongoing sea salinization.

Monthly river flows in Texas for natural and developed conditions

River flow characteristics and computational methods for converting sequences of monthly flows between natural and regulated conditions are explored based on experience in assessing water availability throughout the state of Texas in the United States. Diverse climate, hydrology, economic development, and water management practices across the state combined with continual population growth and implementation of a statewide water availability modeling system makes Texas an excellent case study of stream flow characteristics and modeling and analysis methods that are relevant worldwide. Stream flow is extremely variable, subject to severe multiple-year droughts, intense floods, seasonality, and continuous fluctuation. The effects of population and economic growth, water resources development and management, and climatic variability on river flows vary with different conditions found across the state. The modeling system provides capabilities for adjusting observed river flows to represent natural conditions, simulating regulated flows representing specified conditions of development, and performing statistical frequency and reliability analyses.

Using Bayesian networks for the assessment of underwater scour for road and railway bridges

Flood-induced scour is among the most common external causes of bridge failures worldwide. In the United States, scour is the cause of 22 bridges fails every year, whereas in the UK, it contributed significantly to the 138 collapses of bridges in the last century. Scour assessments are currently based on visual inspections, which are time-consuming and expensive. Nowadays, sensor and communication technologies offer the possibility to assess in real time the scour depth at critical bridge locations; yet, monitoring an entire infrastructure network is not economically feasible. A way to overcome this limitation is to instal scour monitoring systems at critical bridge locations, and then extend the piece of information gained to the other assets exploiting the correlations present in the system. In this article, we propose a scour hazard model for road and railway bridge scour management that utilises information from a limited number of scour monitoring systems to achieve a more confined estimate of the scour risk for a bridge network. A Bayesian network is used to describe the conditional dependencies among the involved random variables and to update the scour depth distribution using data from monitoring of scour and river flow characteristics. This study constitutes the first application of Bayesian networks to bridge scour risk assessment. The proposed probabilistic framework is applied to a case study consisting of several road bridges in Scotland. The bridges cross the same river, and only one of them is instrumented with a scour monitoring system. It is demonstrated how the Bayesian network approach allows to significantly reduce the uncertainty in the scour depth at unmonitored bridges.

Hydrological response to climate change and human activities: A case study of Taihu Basin, China

Climate change and human activities have changed a number of characteristics of river flow in the Taihu Basin. Based on long-term time series of hydrological data from 1986 to 2015, we analyzed variability in precipitation, water stage, water diversion from the Yangtze River, and net inflow into Taihu Lake with the Mann-Kendall test. The non-stationary relationship between precipitation and water stage was first analyzed for the Taihu Basin and the Wuchengxiyu (WCXY) sub-region. The optimized regional and urban regulation schemes were explored to tackle high water stage problems through the hydrodynamic model. The results showed the following: (1) The highest, lowest, and average Taihu Lake water stages of all months had increasing trends. The total net inflow into Taihu Lake from the Huxi (HX) sub-region and the Wangting Sluice increased significantly. (2) The Taihu Lake water stage decreased much more slowly after 2002; it was steadier and higher after 2002. After the construction of Wuxi urban flood control projects, the average water stage of the inner city was 0.16–0.40 m lower than that of suburbs in the flood season, leading to the transfer of flooding in inner cities to suburbs and increasing inflow from HX into Taihu Lake. (3) The regional optimized schemes were more satisfactory in not increasing the inner city flood control burden, thereby decreasing the average water stage by 0.04–0.13 m, and the highest water stage by 0.04–0.09 m for Taihu Lake and the sub-region in the flood season. Future flood control research should set the basin as the basic unit. Decreasing diversion and drainage lines along the Yangtze River can take an active role in flood control.

An integrated framework for prediction of climate change impact on habitat suitability of a river in terms of water temperature, hydrological and hydraulic parameters

The continuous warming observed in recent decades as a result of climate change is posing significant threats to the environment, particularly for freshwater ecosystems. Therefore, it is highly important to predict the impact of this phenomenon on habitat suitability. However, such prediction requires the use of an integrated framework in which different parameters can be incorporated. While 1D modelling has been commonly used in river habit suitability simulations, most 1D mathematical models either do not provide enough information for the area along the rivers or do not consider the impact of river basin management on the river flow characteristics. This study seeks to develop such an integrated framework is in which water temperature and hydrologic-hydraulic parameters are jointly applied to simulate habitat suitability. The modeling setup is based on a combination of the Soil and Water Assessment Tool (SWAT) and international river interface cooperative (iRIC) models, and, due to the importance of the water temperature, the water temperature module in SWAT was modified. To examine the effectiveness of this method, Kikuchi basin is selected as the case study, and two different general circulation models, namely HadGEM2-ES and MICRO5, under two representative concentration pathways are applied to evaluate river habitat suitability under climate change conditions. The results showed a reduction in the river flows, water depths and velocities that have slightly positive effects on the habitat suitability of the Kikuchi river. However, this reduction causes some parts of the river to become dry, so that some of the habitats may disappear as a result of climate change. Moreover, it is shown that the downstream section of the Kikuchi river is more vulnerable to climate change. Therefore, migration of fishes to its upstream section is predicted. Finally, the proposed methodology is strongly recommended for use in modeling of other regions suffering water scarcity.

Using the Monte Carlo method to estimate errors in calculations of river flow characteristics.

Using the Monte Carlo method to estimate errors in calculations of river flow characteristics.

Methods of mathematical modelling for calculating flow characteristics of ungauged rivers in engineering design tasks (by the example of the Khemchik River, Tyva Republic, Russia)

In this study, we assess the results of the application of the deterministic hydrological model Hydrograph for calculating the maximum discharge of various recurrence frequencies at the ungauged mountain catchment of the Khemchik River – Khemchik village (the Tyva Republic, Russia, area 1750 km2). We have assessed the parameters of the model for three main landscapes of the study area. Based on streamflow modelling at two gauged catchments, we have verified the parameters and algorithms of the hydrological mode land the results of modelling are satisfactory. The simulations of streamflow with daily time step for the Khemchik River – Khemchik village was conducted for the period between 1966 and 2012 using meteorological observational data from the Teeli meteorological station. Based on the simulated maximum discharge series, we have constructed the frequency distribution curves and compared with the data on calculations according to the standard methodology of frequency analysis provided in SP 33-101-2003. The modelling-based maximum instantaneous discharges for the frequency interval between 99 and 0.7% are 1.3-5 times higher than the values estimated by the standard methodology. The Ministry of Emergency Situations of the Tyva Republic indirectly confirms the plausibility of model calculations, evidencing the regular flooding of the Khemchik village, which is not predicted by the values obtained with the standard methods.

River flow characteristics and changes under the influence of varying climate conditions

River flow characteristics and changes under the influence of varying climate conditions

Pollution Degree of the Don River Water

The formation and distribution of river flow characteristics in the Don basin have been catholically analyzed, depending on the present-day climatic conditions in the central European Russia. The recent global warming is shown to have resulted in a change in the river flow formation conditions and water resources, as well as in a substantial transformation of the river water regime in the basin. The river water and groundwater chemistry in the basin in 1990–2015 has been considered at the main observation points. The dynamics of river water quality pollution level during the long period is presented. Water pollution characteristics, which make it possible to identify the water quality class and pollution level, have been used to give a generalized estimate of the water quality in the chosen river areas.

Effects of Climate Change and Flow Regulation on the Flow Characteristics of a Low-Relief River within Southern Boreal Climate Area

We investigated how hydro-climatological changes would affect fluvial forces and inundated area during a typical high-flow situation (MHQ, mean high discharge), and how adaptive regulation could attenuate the climate change impacts in a low-relief river of the Southern Boreal climate area. We used hydrologically modeled data as input for 2D hydraulic modeling. Our results show that, even though the MHQ will increase in the future (2050–2079), the erosional power of the flow will decrease on the study area. This can be attributed to the change of timing in floods from spring to autumn and winter, when the sea levels during flood peaks is higher, causing backwater effect. Even though the mean depth will not increase notably (from 1.14 m to 1.25 m) during MHQ, compared to the control period (1985–2014), the inundated area will expand by 15% due to the flat terrain. The increase in flooding may be restrained by adaptive regulations: strategies favoring ecologically sustainable and recreationally desirable lake water levels were modeled. The demands of environment, society, and hydropower are not necessarily contradictory in terms of climate change adaptation, and regulation could provide an adaptive practice in the areas of increased flooding.

Experimental Investigation on the Relationship Between COD Degradation and Hydrodynamic Conditions in Urban Rivers.

Due to extensive pollution and the relatively weak flow replacement in urban rivers, determining how to fully utilize the self-purification abilities of water bodies for water quality protection has been a complex and popular topic of research and social concern. Organic pollution is an important type of urban river pollution, and COD (chemical oxygen demand) is one of the key pollution factors. Currently, there is a lack of research on the relationship between COD degradation and the flow characteristics of urban rivers. In this paper, COD degradation experiments were conducted in an annular flume with Jinjiang River water at controlled flow velocities and the COD degradation coefficients under different hydraulic conditions were analyzed. A good correlation was observed between the degradation coefficient and hydraulic conditions. According to dimensional analysis, the relationship between the COD degradation coefficient and hydraulic conditions such as the flow velocity, water depth, Reynolds number (Re), and Froude number (Fr) was established as . The COD degradation coefficients of the Chishui River in Guizhou Province ranged from 0.175–0.373 1/d based on this formula, and the field-measured values varied from 0.234–0.463 1/d. The error in the formula ranged from 5.4–25.3%. This study provides a scientific basis for the prediction of the COD degradation coefficients of urban rivers.

Morphometric Analysis for Evaluation of Environmental Change and Disaster Reduction of Flood

One indicator of environmental change due to climate change and human activities is changes in river flow and dynamics that can be seen on the visible scale and watershed. This study used geomorphic data which was an important factor for understanding natural processes that occur in efforts to reduced and managed flood risk. Changed in river morphometry would affect the characteristics of river flow, especially in watersheds that have meanders. Analysis was carried out on the Ogan River flow in the Ulak Pandan area and around by comparing flow changes in 1990 and 2016 as well as the used of land at the research site. The morphometry changes were analyzed by changing the width of the river and sinuosity parameters to evaluate the type of change that occurred. The results showed that there was an increase in the width of the river and the sinuosity index value at the same time it appeared that river meanders 5, 6 and 7 represented changes with the highest increase, whereas for land used to changed there was an increase in plantation land and agricultural land. This, indirectly by making changed to land use changed, the destruction of the natural vegetation of the river system results in degradation of river flow, especially in the outer meander arc.

Improved Estuaries Salinity Stratification at Gyeonggi Bay Using Data Assimilation with Finite Volume Coastal Ocean Model (FVCOM)

Gu, B.-H.; Woo, S.-B., and Kim, S.I., 2019. Improved estuaries salinity stratification at Gyeonggi Bay using data assimilation with Finite Volume Coastal Ocean Model (FVCOM). In: Lee, J.L.; Yoon, J.-S.; Cho, W.C.; Muin, M., and Lee, J. (eds.), The 3rd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 91, pp. 416-420. Coconut Creek (Florida), ISSN 0749-0208.Assimilating salinity data into coastal models is very important and salinity vertical change is an important component to coastal forecasting. The goal of this study is to represent the salinity stratification at Gyeonggi Bay (GGB) in South Korea and to improve the accuracy of the prediction in hydrodynamics via data assimilation. The GGB area is located in the Yellow Sea between Korea and China and is a semi-closed estuary that has a tidal range above 7 m with a tidal flat where salt water and fresh water is mixed. Salinity stratification appears at Yeomha channel in GGB because it has characteristics of high tide and strong river flow. To represent the tidal flat and creek in the GGB in this study, the unstructured grid numerical model called Finite Volume Coastal Ocean Model (FVCOM) is employed. The performance of the model results is validated against the measured tide, current, and salinity at the Yeomha channel. In order to improve the numerical results, the salinity observations from the surface and bottom Conductivity Temperature Depth (CTD) data in the Yeomha channel are assimilated into the model only for the 4-day middle period out of total simulation days of 15. The direct comparison results show the clear effect of data assimilation for salinity stratification along vertical salinity, and the improvement of salinity profile lasts for 1 day after the end of data assimilation. The salinity stratification in the coastal are also improved as the number of observations and/or data assimilation periods is increased. These results are expected to improve the coastal forecasting system over the GGB area when applied the data assimilation scheme in to the forecasting system.

Long-Term Changes of Hydrological Variables in a Small Lowland Watershed in Central Poland

Climate-induced changes in small watersheds are still not well researched because long-term datasets are usually missing for these watersheds. Such studies can, however, improve our understanding of the watershed response to climatic changes at such a small scale being transparent. In this study, we investigate trends in temperature, precipitation and river-flow characteristics in a small watershed, typical for Central Poland, with 53 years of observations (1963–2015) using the Mann-Kendall test. Particularly, we examine whether any trends in hydro-meteorological variables can be identified, and if any associated changes in water resources in this region can already be observed. We found that this short period already allows for detecting some changes in hydro-meteorological variables. These changes could be characterized by a significant increase in the mean annual air temperature on a daily basis, and a significant decrease in the mean annual discharge on a daily basis and in the minimum annual discharge on a daily basis. Yet, no significant trend could be detected for the total annual precipitation, the maximum summer rainfall, and the maximum annual discharge on a daily basis. These findings indicate that water resources are decreasing in this region, which affects natural habitats, agriculture and local communities.

Flow characteristics of intermittent rivers in Slovakia

Abstract Flow characteristics of intermittent rivers in Slovakia. Intermittent rivers are rivers that cease to fl ow, i.e. temporary, ephemeral, seasonal, and episodic rivers. Analysis of hydrological regime of such rivers is pivotal in assessment of water resources because changes in fl ow characteristics of such rivers may affect neighboring catchments or the entire region through changes in water supply reservoirs such as lakes, wetlands and mosses. Recently, an increasing number of intermittent rivers and ephemeral streams (IRES) and an elongation of the zero- -fl ow events has been observed in Europe due to climatic changes and anthropogenic influence. Intermittent rives in Slovakia were studied in the paper using statistical methods. The characteristics of the zero-fl ow period, of duration of the longest annual zero-fl ow event and of timing of such events were derived. The circular statistics were helpful in recognition of the dates of occurrence of such events. The comparative analysis between catchments was performed. The variability in precipitation and evapotranspiration and the increasing temperature were identified as the possible drivers of the fl ow intermittence in these catchments. The research was performed within the COST Action SMIRES (Science and Management of Intermittent Rivers & Ephemeral Streams).