Maximum Discharge Values Research Articles

Developing A Series of Weirs System to Improve Hydraulic Properties and Generate Hydroelectric Power in Rivers

In present paper, attempts were made to develop a system of weirs along Euphrates River in Iraq to solve the problem of the deficit in power and water resources. Geometric numerical models were created with geographic information system (GIS) with digital elevation model (DEM). The model includes visual basic programming to evaluate the power potentials according to an economic methodology based on the cost-benefit ratio (CBR). It estimates the cost, power profits, and determines the optimal height and number of small dams along the study reach. A system of three dams with a (4.3 m) in height can generate expected power of (45 MW) within (99%) of CBR. The system is simulated with the numerical model (HEC-RAS) to evaluate the river behavior with minimum, average, and maximum discharge values (270, 543, 815 m3/s) and study the hydraulic effect on the river. The hydraulic properties improve by (28%), the average depth increase with (27%), and a decrease in the variation caused by discharge changes. The river tendency is to store water with limited expansion in the surface area. The average surface area expands with (5%), the average storage increase with (35 %) especially in cases of low discharges.

The application of the hybrid copula-GARCH approach in the simulation of extreme discharge values

Statistical analysis and simulation of annual maximum discharge values, while considering the corresponding maximum daily rainfall, provide a comprehensive view of flood management. This research presents the application of copula functions for simulating and modeling two variables of annual maximum discharge and corresponding precipitation. In this research, the performance of copula-based models and ARCH-based models including VAR-GARCH, copula, and copula-GARCH models was then evaluated to simulate the annual maximum discharge values. The simulation results of all three models were evaluated using NSE and NRMSE statistics. According to the 95% confidence intervals, the accuracy of all three models was confirmed. The correlation results of the studied pair variables confirmed the possibility of using copula-based models. The results of simulations revealed that a higher accuracy of the copula-GARCH approach compared with two models copula and VAR-GARCH. Considering 76% efficiency (NSE = 0.76) of the copula-GARCH approach, the results indicated 20 and 2.7% improvements in the performance of the proposed approach compared to both VAR-GARCH and copula models. The results also illustrated that by combining nonlinear ARCH models with copula-based simulations, the reliability of simulation results increased. The results obtained in this study suggest that the proposed method is very effective for increasing the certainty of frequency analysis of two variables. Because the copula-GARCH approach simulates the average values, the first and third quarters, as well as the amplitude of changes of 5 and 95% of the data better than the other two models.Graphical abstractViolin plot of AMD series in copula scale

The quantitative effect of blue lenses on pediatric photoparoxysmal response – An electroencephalographic cohort study

PurposeTo determine and quantify the effect of blue lenses (Z1) on photosensitivity (PS) suppression in patients aged 5-18 years with and without epilepsy. MethodsThe retrospective cohort study was carried out in 100 pediatric patients aged 5-18 years with grade 4 PS assessed with EEG for medical indications. All EEG procedures were carried out and recordings assessed by two independent researchers. The study cohort was divided into groups with and without the diagnosis of epilepsy. The overall effect of the Z1 lenses on photoparoxysmal response (PPR) was determined by directly comparing the maximum discharge values in each patient without and with Z1 lenses in a within-subject design yielding the index of overall improvement (IOI). The differences in PS suppression by brain region and side were assessed by an additional between-subject comparison of age groups (below and above 14 years). Then, overall findings were compared with the PPR change criteria developed in 2006 by Capovilla (PPR disappearance, persistence, or attenuation) which warranted another subset analysis. Finally, in a between-subject design, we assessed whether the presence of epilepsy affects the intensity of PPR in children with PS, compared to non-epilepsy children. ResultsThe IOI in the entire cohort was 66.1±2.5% (P<0.001). There were no significant differences in IOI between the left and right hemispheres, between the age groups, and between the epilepsy and non-epilepsy groups, despite some qualitative variation. With reference to literature findings, whereas median IOI were comparable in PPR disappearance and attenuation subsets, they differed significantly from the median IOI in the PPR persistence subset. ConclusionUsing Z1 lenses results in neither a complete PPR disappearance, nor a complete lack of effect. However, the correlation between the quantified PS suppression and the Z1 filter may be expected to become a valuable piece of information for both clinicians and manufacturers.

Impact of the Mean Daily Air Temperature Calculation on the Rainfall-Runoff Modelling

Conceptual rainfall-runoff models besides precipitation and discharge data generally require estimates of the mean daily air temperature as input data. For the estimation of the mean daily air temperature, there are different methods available. The paper presents an evaluation of the impact of the mean daily air temperature calculation on the rainfall-runoff modelling results. Additionally, other measured variables and rating curve uncertainty were assessed. Differences in the mean daily air temperature values were evaluated for the 33 meteorological stations in Slovenia and additional investigations were conducted for four selected meso-scale catchments located in different climates. The results of the application of four equations for the mean air temperature calculation yielded the mean absolute error values between 0.56–0.80 °C. However, the results of rainfall-runoff modelling showed that these differences had an almost negligible impact on the model results. Differences in the mean simulated discharge values were no larger than 1%, while differences in the maximum discharge values were a bit larger, but did not exceed 5%. A somewhat larger impact on the model results was observed when precipitation and water level measurements’ uncertainty was included. However, among all analysed input data uncertainties, the rating curve uncertainty can be regarded as the most influential with differences in the simulated mean discharge values in the range of 3% and differences in the maximum discharge values up to 14%.

Dynamics of erosion-accumulation processes along the stream bed of Turiya River (Kovel hydropost)

The article reflects the results of the study of deformations of the stream bed of the Turiya River (Kovel Hydropost, hydro range No. 5) during 1983–2018. For this purpose, multiple cross-sections of the channel and various combined flow curves were constructed and analyzed, the levels of water in the river, the relationships between the course of erosion-accumulation processes along the course and the dynamics of natural and anthropogenic factors are revealed. The information base of the study was the theoretical basis of the doctrine of channel processes, which are substantiated in the works of foreign and Ukrainian scientists, the materials of our own observations, data from the Volyn Center for Hydrology and Meteorology (hereinafter VCGM). In the process of solving the tasks, the methods of comparative analysis, synthesis, graphic, mathematical and statistical methods were applied; the system approach was applied. During the study it was established that during the specified time interval in the stream bed there was an alternation of erosion and accumulation processes, which was expressed by the alternation of periods of some erosion of the stream bed and its siltation. The transverse profiles of the Turiya stream bed indicate that during the period 1983–1988, mainly accumulative processes prevailed in the channel, and in the following period (1988–2008) they changed to erosion ones. In recent years, rechargeable processes have become dominant and the profile of the stream bed in 2018 has come closer to its stream bed in 1988. The flow and water level curves of Turiya confirm our conclusions about trends in erosion-accumulation processes along the stream bed. During the periods 1983–1988 and 1996–2000, the accumulation processes dominated, and at the interval of time from 1988 to 1996 and in 2000–2008 erosion processes dominated. The 2009, 2012, 2013, 2014, 2017 curves are in almost one field, which attests to the stability of the Turiya River over the last decade. The development of channel deformations depends, mainly, on the hydrological regime of the river. The dynamics of erosion-accumulation processes along the river Turiya is consistent with the long-term regime of its maximum runoff: in the 80-ies of the last century a significant fall in the values of maximum discharge (some decrease in annual precipitation, the influence of the Kovel reservoir) was observed, which led to their erosion. Compared to this time period, around the 1990s and during the 2000s, the values of maximum discharge increased slightly. As a consequence, the eroding ability of the watercourse during floods and freshets increased, which slightly increased the cross-sectional area of the channel. In the last four years, the values of maximum discharge have been significantly lower than normal, and as a result erosion processes have weakened. Reduction of the maximum discharge of the Turiya River, absence of runoff during the 2015–2018 boundary, dominance of accumulative processes in the channel leads to eutrophication of the watercourse, which, in turn, reduces its transport capacity and contributes to the further accumulation of solids. If this trend continues in the future, then the risks of flooding the Turiya floodplains in the event of heavy floods or freshets will increase. Keywords: Volyn region, hydrological regime, hydropost, water flow and water level curves, transverse profile of river bed, Turiya River, surface runoff, stream bed deformations.

ASSESSMENT OF MAXIMUM INSTANT DISCHARGE OF VARIOUS FREQUENCY AT UNGAUGED MOUNTAINOUS RIVER KHEMCHIK (TUVA REPUBLIC) BASED ON MATHEMATICAL MODELLING

Abstract: the article presents the results of application of distributed deterministic hydrological model Hydrograph for estimation of maximum discharge values of different frequency at the ungauged catchment of the Khemchik River (Khemchik village, Tuva Republic). The catchment area is 1750 km2 , the average and maximum elevation — 2200 and 3600 m, respectively. Due to the lack of detailed information, a schematization of the catchment and the parameterization of the model are proposed, based on general ideas about the water balance and the processes of runoff formation of the main landscapes — rocky talus, coniferous forest and steppe. Parameters and algorithms are verified based on the results of streamflow modeling at two studied catchments: the Tapsy River — Kara-Khol (302 km2 ) and the Khemchik River — Iyme (25500 km2 ). Modelling of runoff formation processes with daily time step for the Khemchik River — Khemchik village was conducted for the period 1966–2012 using observational data at Teeli meteorological station. For the transition from daily to instant discharges, the dependence of the observed values of instant and daily streamflow at the studied gauges has been applied. On the basis of simulated discharge series, the frequency curve was built and the obtained curve was compared with the calculation data according to the standard methodology SP 33-101-2003 “Determination of the main calculated hydrological characteristics” using the analogue river. Simulated maximum instant discharges for entire frequency interval of up to 1% are 1.3–5 times higher than the values obtained by standard methodology SP 33-101-2003. The results of model calculations is indirectly confirmed by the evidences of regular flooding of the Khemchik village provided by the Ministry of Emergency Situations of the Tuva Republic, which is not predicted by the values obtained by the standard methods.

Coping with Extreme Events: Effect of Different Reservoir Operation Strategies on Flood Inundation Maps

The need of addressing “residual flood risk” associated with structural protection measures, such as levee systems and flood-control reservoirs, has fostered actions aimed at increasing flood risk awareness. Structural measures have lowered risk perception by inducing a false sense of safety. As a result, these structures contribute to an underestimation of the “residual risk”. We analyze the effect of different reservoir operations, such as coping with drought versus coping with flood events, on flood inundation patterns. First, a hydrological model simulates different scenarios, which represent the dam regulation strategies. Each regulation strategy is the combination of an opening of the outlet gate and of the initial water level in the reservoir. Second, the corresponding outputs of the dam in terms of maximum discharge values are estimated. Then, in turn, each output of the dam is used as an upstream boundary condition of a hydraulic model used to simulate the flood propagation and the inundation processes in the river reach. The hydraulic model is thus used to determine the effect, in terms of inundated areas, of each dam regulation scenario. Finally, the ensemble of all flood inundation maps is built to define the areas more prone to be flooded. The test site is the Casanuova dam (Umbria, central Italy) which aims at: (i) mitigating floods occurring at the Chiascio River, one of the main tributaries of Tiber River, while (ii) providing water supply for irrigation. Because of these two competitive interests, the understanding of different scenarios generated by the dam operations offers an unique support to flood mitigation strategies. Results can lead to draw interesting remarks for a wide number of case studies.

Peak flood estimation under overtopping and piping conditions at Vahdat Dam, Kurdistan Iran

Estimation of maximum discharge and time of transfer dam break wave are among the main factors in provision of emergency action plan and safety assessment of dams. Most dam breaks begin with a breach in the body of the dam or flood overtopping. Estimation of maximum discharge for determining affected areas and also determination of hazards due to the dam break are essential issues. In this research, the dam break of Vahdat Dam located in Kurdistan, Iran, and in neighborhood of Sanandaj City was simulated by integrating ArcMap and HEC-RAS software and field observations. The necessary data was collected from the corresponding organizations. The Manning coefficient of the Gheshlagh River at downstream of the dam was estimated using the Manning coefficient relationships and field observations and measurements. The breach dimensions were determined using the conventional empirical relationships. The dam breaks in both overtopping and piping states were simulated. The maximum discharge values obtained from the modeling and empirical relationships were compared. The results indicated the substantial effect of selecting break types on the hydraulic characteristics of dam break wave in the river and downstream areas. While in the case of break due to the breach, selection of the methods for calculation of breach dimensions would affect the break and these relationships in various conditions would give different breach dimensions.

A modified hydrodynamic model for routing unsteady flow in a river having piedmont zone

Abstract Existence of piedmont zone in a river bed is a critical parameter from among numerous variations of topographical, geological and geographical conditions that can significantly influence the river flow scenario. Downstream flow situation assessed by routing of upstream hydrograph may yield higher flow depth if existence of such high infiltration zone is ignored and therefore it is a matter of concern for water resources planning and flood management. This work proposes a novel modified hydrodynamic model that has the potential to accurately determine the flow scenario in presence of piedmont zone. The model has been developed using unsteady free surface flow equations, coupled with Green-Ampt infiltration equation as governing equation. For solution of the governing equations Beam and Warming implicit finite difference scheme has been used. The proposed model was first validated from the field data of Trout Creek River showing excellent agreement. The validated model was then applied to a hypothetical river reach commensurate with the size of major tributaries of Brahmaputra Basin of India. Results indicated a 10% and 14% difference in the maximum value of discharge and depth hydrograph in presence and absence of piedmont zone respectively. Overall this model was successfully used to accurately predict the effect of piedmont zone on the unsteady flow in a river.

Propagation of rating curve uncertainty in design flood estimation

AbstractStatistical flood frequency analysis is commonly performed based on a set of annual maximum discharge values which are derived from stage measurements via a stage‐discharge rating curve model. Such design flood estimation techniques often ignore the uncertainty in the underlying rating curve model. Using data from eight gauging stations in Norway, we investigate the effect of curve and sample uncertainty on design flood estimation by combining results from a Bayesian multisegment rating curve model and a Bayesian flood frequency analysis. We find that sample uncertainty is the main contributor to the design flood estimation uncertainty. However, under extrapolation of the rating curve, the uncertainty bounds for both the rating curve model and the flood frequency analysis are highly skewed and ignoring these features may underestimate the potential risk of flooding. We expect this effect to be even more pronounced in arid and semiarid climates with a higher variability in floods.

Experimental hydrological studies of processes of failure of beaver dams and pond draining

Beaver dams on small rivers significantly alter their hydrological regime. Formation of maximum break discharges on small rivers and flooding of areas are one of the detrimental consequences caused by the failure of such dams. Based on our survey of 11 dams and ponds in the Vereshchaginskii district (Perm oblast), as well as on cartographic modeling of 20 ponds, the dependences of the pond basin volume on the length of the pond and the maximum height of the dam have been established, which can be used to estimate the approximate volume of these ponds. When the dam height changes from 0.5 to 3.4 m and its length changes from 5 to 50 m, the volume of the pond basin alters from 0 to 850 m3. According to the results of artificial dam failure, the following aspects have been established: the nature of simulated flood propagation, the dependence of hydrological characteristics on stages; runoff hydrographs and volumes, as well as the nature of the drained pond bed. It has also been found that the development of the closure channel in the body of dams is unlikely to take place and that erosion mainly occurs on riverbank soils. Based on calculations, it has been revealed that the quantities of natural full-scale break discharges are equal to the maximum rain flood discharge with a 10% probability of exceedance. Full-scale break discharges differ from those calculated according to the hydraulics formulas by 10 to 30%. The maximum discharge values during our experiment ranged from 50 to 500 L/s; the amount of time to empty the ponds varied from 100 to 180 min.

Bivariate flood frequency analysis using the copula function: a case study of the Litija station on the Sava River

As an alternative to the commonly used univariate flood frequency analysis, copula frequency analysis can be used. In this study, 58 flood events at the Litija gauging station on the Sava River in Slovenia were analysed, selected based on annual maximum discharge values. Corresponding hydrograph volumes and durations were considered. Different bivariate copulas from three families were applied and compared using different statistical, graphical and upper tail dependence tests. The parameters of the copulas were estimated using the method of moments with the inversion of Kendall's tau. The Gumbel–Hougaard copula was selected as the most appropriate for the pair of peak discharge and hydrograph volume (Q-V). The same copula was also selected for the pair hydrograph volume and duration (V-D), and the Student-t copula was selected for the pair of peak discharge and hydrograph duration (Q-D). The differences among most of the applied copulas were not significant. Different primary, secondary and conditional return periods were calculated and compared, and some relationships among them were obtained. Copyright © 2014 John Wiley & Sons, Ltd.

Assessment of permeability and injection depth at the Atasu dam site (Turkey) based on experimental and numerical analyses

This study was performed in order to evaluate the permeability of the basalts and pyroclastics and the maximum depth of grout injection at the Atasu dam site, Turkey, using the equations of Kiraly and Hoek and Bray based on values obtained from Lugeon tests. In order to evaluate maximum discharge values and depth of injection, seepage analyses were performed using the finite element technique for each 10 m up to 100 m. The results indicate that to establish an impermeable zone at the dam site, the depth of injection should be taken as 50 m for the left and right slopes and 40 m for the river bed.

Study on Solidification Technology and Safety Assessment for Sewage Sludge

In the light of heavy metal contents such as Pb and Zn in municipal sewage sludge exceeding the allowed maximum value of discharge wastes in China, new solidification technology was taken to solidify sewage sludge; its effect and safety were studied as well. The experiment results showed that the 28 days compressive strength of sewage sludge concretion were more than 40 MPa by this solidification method and a relative excellent advantage of road performance properties such as residual Marshall values and rutting resistance for asphalt mixture prepared with sewage sludge concretion. Meanwhile, its solidified heavy metal infusion met the requirements of the national standard, in other words, heavy metal ions receiving an effective bound and stable solidification.

Regionalization of floods in New Brunswick (Canada)

This study uses the method of peaks over threshold (P.O.T.) to estimate the flood flow quantiles for a number of hydrometric stations in the province of New Brunswick, Canada. The peak values exceeding the base level (threshold), or `exceedances', are fitted by a generalized Pareto distribution. It is known that under the assumption of Poisson process arrival for flood exceedances, the P.O.T. model leads to a generalized extreme value distribution (GEV) for yearly maximum discharge values. The P.O.T. model can then be applied to calculate the quantiles XT corresponding to different return periods T, in years. A regionalization of floods in New Brunswick, which consists of dividing the province into `homogeneous regions', is performed using the method of the `region of influence'. The 100-year flood is subsequently estimated using a regionally estimated value of the shape parameter of the generalized Pareto distribution and a regression of the 100-year flood on the drainage area. The jackknife sampling method is then used to contrast the regional results with the values estimated at site. The variability of these results is presented in box-plot form.

Partial discharges in lapped polymer taped insulation impregnated with supercritical helium

Apparatus has been designed and constructed to evaluate the high-voltage parameters of lapped cable models impregnated with supercritical helium for pressures up to 1.5 MPa and for temperatures to 4.2 K. The tape materials studied are as follows: high-density polythene, Valeron (cross-laminated polythene film), polypropylene, Nylon 11 and polysulphone with limited tests using polycarbonate. These were selected on previously published parameters related to mechanical properties, lappability and low loss. The variation of the maximum value of discharge with applied alternating voltage is obtained, and also the variation of inception stress (1 pC and 5 pC) with helium density and pressure. Although most attention has been given to tapes wrapped on a stainless-steel electrode, the influence of various conductor screens has also been investigated.In an AC superconducting cable the attainment of the highest possible inception stress is important, and the order of merit of the materials investigated is: Valeron, polypropylene, high-density polythene, polysulphpne and, finally, Nylon 11.