Journal of Water Resources Engineering
Year:2012 | Volume:5 | Issue:14|Papers Count:8

Vulnerability assessment is applied to identify susceptible areas of aquifers to contamination. Drastics model was designed based on seven components: Depth to water table (D), Feeding pure (R), Aquifer media (A), Soil environment (S), Topography (T), unsaturated environment (I), and Hydraulic conductivity (C). The aims of this study are: evaluating the Shahrekord aquifer vulnerability using DRASTIC model in GIS environment, verification of DRASTIC model and investigating the effect of nitrate and phosphate concentration seasonal variations on the accuracy of prediction by drastic model. In order to determine the influence layers, a score was given to each of parameters and the final maps were added together. The final vulnerability map show that 11.5%, 79.6%, and 8.9% of the study area have very low, low and moderately pollution potential (vulnerability), respectively. Comparison of vulnerability map with maps of seasonal variations of nitrate and phosphate concentrations show that the results of DRASTIC model somewhat depends on sampling time. Therefore, correlation of nitrate or phosphate with DRASTIC map shows significant differences during the years. The greatest and lowest correlation occursin spring and at the end of summer, respectively. Thus, the sampling time must be considered in drastic model.

As flooding events and subsequent damages are increasing and flood control plans are costly, determination of control scenarios and their prioritization in terms of type and spatial distribution in line with watershed management concepts are essential. The effect of various flood control scenarios may be simulated using the integrated hydrologic and hydraulic models, and selection of the most appropriate scenario can be based on an objective function involving costs and damages. However, information needed for an accurate estimation of costs and flood damages is not readily available. Thus, in this research, the cost-benefit ratio was defined as a function of hydrologic factors. For an assessment of such benefit to cost ratios, and determination of flood control scenarios in the Rudzard Watershed, two main scenarios of upgrading rangelands as well as conversion of rangeland to farm land and orchard were considered in view of management and improvement of vegetative cover as parts of the biological measures. The ModClark distributed hydrologic model and the HEC-RAS hydraulic model were used for the sub-watershed and river routing, respectively. The combined model was run based on the new land use changes in each scenario, and the peak outlet discharge was determined. The results indicated that rangeland improvement scenario was more effective in reducing the peak discharges of both sub-watershed and main watershed outlets. Abgelal and Mashin sub-watersheds were identified as the two main candidates for land use improvement at the sub-watershed scale. However, Mashin and Damdeli sub-watersheds were of primary interest to reduce the peak discharge at the outlet of the entire watershed, while Abgelal and Alekhorshid came next.

However chlorination of water is a successful and popular worldwide method for disinfection, especially in developing countries, but chlorination can produce trace amounts of byproducts, such as trihalomethanes (THMs). Because of harmful effects of trihalomethanes, measuring of these compounds in water from health and the environmental aspects is important. In this research, water was sampled from 20 stations in different parts of Shiraz in four dates (80 samples). In these samples, pH, temperature, total organic carbon and trihalomethanes were measured with three replications.Results showed that maximum concentrations of trihalomethanes (in chloroform) in drinking water was about 39 mgl-1 which is less than maximum permissible limit (40 mgl-1).Maximum trihalomethanes were belonged to stations which is used surface water resource (water of Doroodzan dam reservoir) with high organic matter. Statistical analysis showed that there was a linear relationship between chlorine, organic matter and pH with trihalomethane and the most effective parameters were organic matter, pH and chlorine, respectively. The amounts of trihalomethane in different stations were significant in 1% level, but there was no significant difference in various time.

Awareness of the existence of a complex behavior and the variability of the suspended sediment particle size are the most important factors in modeling of sediment transport. Therefore, the present study had aimed to investigate the influence ofdischarge competence on the suspended sediment particle size distribution changes in the Kojour River draining from a 50,000 ha of Educational and Research Forest Watershed of the TarbiatModares University. The study was conducted on a daily and storm bases. The flow velocity was measured by using a current meter and floaters in the normal and flood durations, respectively. The suspended sediment was determined through sampling using the integration method, and the particle size distribution of the suspended sediment was ultimately analyzed based on the Stokes’ law using the modified pipette method. The relationship between the discharge and particle size distribution of the suspended load in the study period was assessed by applying the bivariate regression method supported by different statistical criteria. The results revealed that the best correlation was established between the discharge and silt in the normal situations, and the discharge and sand, silt and clay under storm conditions, respectively, with corresponding correlation coefficient, relative estimation errors, verification errors, and coefficient of efficiency of 0.46, 0.63, 129.36, 32.66, 46.00, 49.61, and 0.95, 0.93, respectively.

Perceptron and generalized regression neural network (GRNN) have been used to predict the maximum depth of scour around bridge piers. Levenberg-Marquardt and Momentum as training algorithms and Sigmoid and Tanh as activation functions have been used in this study. Many studies have been conducted recently using the artificial intelligence techniques to predict bridge pier scour. Application of the circular pier shape and experimental data in place of the real data are the weaknesses of most of the previous stidies. Therefore, the rectangular-based piers with rounded edges, and the sharp-edged piers have been studied in the present research in addition to the cylindcal piers. Furthermore, 475 real data have been used to build and verify the neural models. In contrast to the studies in which the trial and error were used to determine the number of hidden layers, the genetic algorithm was used in this study to determine hidden layer neurons. The result of all neural models indicated that the GRNN model estimates equilibrium scour depth more accurately than the other models. To examine the accuracy of the GRNN model, some popular empirical models such as the Laursen and Toch, Shen, Breusers et al., Froehlich, Melville and Melville, and Chiew have also been used. Although the Froehlich model provided a better accuracy than those of the others, the result developed by the GRNN model were in better agreement with the real data. The sensitivity analysis indicated that the mean velocity had a greater influence on equilibrium scour depth than the other independent parameters.

Inlets play an important role in controlling sediment movement and its distribution in coastal areas. Therefore, recognizing effective factors in the hydro-dynamicity of inlets known as transmission process and determining the geometry and formation of inlets are of paramount importance. The undulations of water and tidal waves are among the major factors shaping an inlet. The purpose of this study is to find out how these two factors could interactively affect the sediment. To this end, a coastal basin that is connected to the open sea through a mouth is simulated in Mike 21.3 software. For this simulation, a 10*50 meter un-structured triangular flexible mesh in a finite difference model at two seconds intervals was used; undulations and tidal waves were sent to the mouth of the inlet simultaneously. By simulation, the morphology of the inlet changes in a way that with the passage of time reaches equilibrium, hence, there would be an ideal inlet. Also, by means of characteristic non-dimensionalHw/Ht, the dominant parameter in the inlet can be determined in the inlet. For calculation of morphological changes in inlet of estuary, first tidal fluctuations as a single parameter and then wave parameter separately considered, then two parameters together considered, the results show that for two cases, the morphological changes are the same.

High velocity of fluid along with the severe head loss causes several turbulences in the flow and may lead to the occurrence of cavitation phenomenon in hydraulicstructuresand severe destructions in some parts of them. In this paper, pressure fluctuations, which are a product of severe turbulences, their processes and cavitation phenomenon in the service gate slot zone of physical models of bottom outlets of the Karoun4 and the Gotvand-e Olya Dams was investigated. Theratioof length to width of the slot1.75 and 2 and in 10,30,50,70 and %100 openings and in different 2, 3 and 4 meter-heads, and is based %0.1 probability levels had been investigated and compared. The results obtained indicated that in the30, 50, and %70 gate openings, cavitation index is the minimum, and in %10 and %100itis the maximum. Also, the piezometer, which is closer to the gate edge, is subject to more fluctuations, and the critical point of pressure fluctuations are transferred to the higher points with anincrease in gate opening. Dimensionless coefficient of pressure fluctuations (C'p) with ratio1.75, in %30 opening and ratio of 2, in%10 opening is the maximum that indicates compaction and pressure beats to the structure at this openings.

By using an innovative technique, an explicit numerical solution for an incompressible steady flow by the finite volumes method on unstructured grid is developed. The two-dimensional forms of the Navier-Stokes equations with an application of the artificial compressible method based on a new uncoupled method are solved. To verify the efficiency and accuracy of the developed incompressible flow solver, two steady test cases are simulated: Firstly, in viscid flow around a cylinder is considered. Secondly, a case of steady viscous flow at low Reynolds numbers on square cross-section cavity flow is modeled. To assess the accuracy of the computed results of the introduced algorithm, they are compared with the available results of the numerical and analytical solutions reported in the literature for the selected benchmark test cases.