Showing 48 results for River
R. Sadeghi Talarposhti, R K. Ebrahimi, A. Horfar,
Volume 25, Issue 4 (3-2022)
Abstract
Protection of rivers’ water quality as the most accessible source of the water supply has always been considered. In this paper, self-purification and the pollution decay coefficient values of Talar River, IRAN were studied based on field measurement of DO, BOD, pH, EC, Nitrate, Phosphate, and Temperature, in four seasons of the year 2018, in tandem with the river simulation and its calibration using QUAL2Kw model and the Streeter-Phelps method. In addition to the modeling and analysis results, the measured laboratory data values of the river water samples are also presented. Based on the results, the DO variations were ranged from 5.15 in summer to 7.47 mg/l in spring and BOD variations ranged from 1.88 in fall to 7.9 mg/l in summer. Also, according to the Streeter-Phelps method the decay coefficient values varied from 1.57 (1/day) in spring to 9.63 (1/day) in fall. The values of the Talar River decay coefficient also varied from 2 in fall to 7.7 (1/day) in summer involving the QUAL2Kw model.
S. Toghiani Khorasgani, S. Eslamian, M.j Zareian,
Volume 25, Issue 4 (3-2022)
Abstract
In recent decades, water scarcity has become a global problem due to the growth of the world's population as well as the increase in per capita water consumption. Therefore, planning and managing water resources to prevent potential risks such as floods and drought in the future is one of the important measures of water resources management. One of the important measures to avoid potential risks and predict the future is rainfall-runoff modeling. The objective of this study was to investigate the efficiency of the WetSpa hydrological model in estimating surface runoff in the Eskandari watershed, which is one of the important sub-basins of the Zayandehrood watershed. In this study, Daran and Fereydunshahr synoptic stations have been used to collect meteorological information in the Eskandari watershed. Also, to study the flow of the Plasjan river, daily data of Eskandari hydrometric station, located at the outlet of the basin, have been used. Climatic data along with digital maps of altitude, soil texture, and land use were entered as input to the WetSpa model. Finally, the ability of the WetSpa model was evaluated in estimating river surface runoff. The observed flow at the basin outlet in the hydrometric station was used to evaluate and calibrate the model. The model was calibrated for the statistical period (1992-2000) and its validation was performed for the statistical period (2001-2004). In the calibration period, the trial and error method were used to calibrate the model parameters. The simulation results showed a good correlation between the simulated flow and the measured flow. In the present study, the Nash Sutcliffe coefficient in the calibration and validation stages was equal to 0.73 and 0.75, respectively which shows the good and acceptable ability of the model in estimating the surface runoff of the study basin.
M. Heydari, M. Bahrami Yarahmadi, M. Shafai Bejestan,
Volume 26, Issue 2 (9-2022)
Abstract
Bed shear stress is one of the most important hydraulic parameters to determine the amount of bed and suspended load and the bed and bank scouring in rivers. Bed shear stress depends on bedforms (ripples, dunes, and anti-dunes) in alluvial rivers. In this study, the effect of artificial ripple bedforms on bed shear stress has been investigated. Two types of uniform granulation with average sizes (d50) of 0.51 and 2.18 mm were used to roughen the surface of the artificial ripples. The bedform length and height were 20 and 4 cm, respectively. The angles of its upstream and downstream to the horizon were selected equal to 16.4 and 32 degrees, respectively. Different flow rates (Q= 10, 15, 20, 25, and 30 l/s) and different bed slopes (S= 0, 0.0001, 0.0005, 0.001, and 0.0015) were examined. The results showed that by increasing the particle size on the bed surface, total shear stress (tb ), grain-related bed-shear stress (t¢b ), and form-related bed-shear stress ( t²b ) increase. The value of tb , t¢b , and t²b in bed form roughened by sediment size of 2.18 mm were, on average, 22.38, 30.86, and 22.3% more than the bed form roughened by sediment size of 0.51 mm, respectively.
S. Parvizi, S. Eslamian, M. Gheysari, A.r. Gohari, S. Soltani Kopai, P. Mohit Esfahani,
Volume 26, Issue 3 (12-2022)
Abstract
Investigation of homogeneity regions using univariate characteristics is an important step in the regional frequency analysis method. However, some hydrological phenomena have multivariate characteristics that cannot be studied by univariate methods. Droughts are one of these phenomena their definition as univariate will not be effective for risk assessment, decision-making, and management. Therefore, in this study, the regional frequency analysis of drought was studied in multivariate methods using SEI (Standardized Evapotranspiration Index), SSI (Standardized Soil Moisture Index), and SRI (Standardized Runoff Index) indices in the Karkheh River basin from 1996 to 2019. The indices calculated probabilistic distribution between the variables of evapotranspiration, runoff, and soil moisture using multivariate L-moments method and Copula functions and considered meteorological, agricultural, and hydrological droughts simultaneously. The results of multivariate regional frequency analysis considering the Copula Gumbel as the regional Copula showed that the basin is homogeneous in terms of severity of SEI-SSI combined drought indices and is heterogeneous in terms of severity of SEI-SSI combined drought indices. However, after clustering the basin into four homogeneous areas in terms of characteristics of SPI (Standardized Precipitation Index), the basin is homogeneous in all areas in terms of univariate SEI, SSI, and SRI indices and is heterogeneous in the third and fourth clusters of SRI and SSI drought indices. Pearson Type (III), Pareto, normal, and general logistics distribution functions were found suitable to investigate the characteristics of SEI, SSI, and SRI drought indices in this case. Finally, large estimates of the types of combined droughts and their probability of occurrence showed that the northern and southern parts of the Karkheh River basin will experience short and consecutive droughts in the next years. Droughts in areas without meteorological data can be predicted in terms of joint probability using the multivariate regional frequency analysis method proposed in this study.
M. Pasandi, H.r. Pakzad, A.m. Halvaie Lengeh, M.r. Taherizadeh,
Volume 26, Issue 4 (3-2023)
Abstract
The relationship between the concentration of heavy metals and physicochemical factors was studied in the fine-grained sediments of the tidal section of the Mehran delta where mangrove trees have grown. Surface sediments of the tidal zone of the Mehran delta were sampled. The grain size distribution, calcium carbonate, organic matter contents, pH/Eh, and heavy metals concentration were determined in the mud fraction of the sediments. The presence of high calcium carbonate in sediments is an effective factor in the abundance of Mn, Cd, and Pb. Clay and organic matter as adsorptive have contributed to the high concentration of Zn, Cu, while Fe oxy-hydroxides have affected the concentration of Co, Cr, and Ni. According to the index of Enrichment Factor (EF), the average enrichment of the elements in the studied sediments from high to low order is Cr, Ni, Cd, Zn, Mn, Pb, Co, and Cu. According to the Pollution Load Index (PLI), none of the delta sediments including sediments from inside and outside of the mangrove forestare classified as polluted to the heavy metals. According to the Igeo Index, most samples, and only Cd, Cr, and Ni show slight pollution in some samples. Accordingly, there is no current threat of contamination of potentially toxic elements of natural and anthropogenic origins to the mangrove environment and Mehran delta.
M. Dorfeshan, A.r. Masjedi, M. Heidarnejad, A. Bordbar,
Volume 27, Issue 3 (12-2023)
Abstract
Piano key overflows have a high discharge capacity. Proper design of these overflows requires sufficient accuracy in predicting the type of overflows. In this study, experiments were performed in a rectangular laboratory flume made of Plexiglas to investigate the effect of the relative length and width of the two-cycle piano switch overflow crest on the discharge coefficient. In present research, the flow intensity coefficient was investigated by installing a rectangular piano switch overflow with relative crest lengths of 0.8, 1, and 1.2 and relative crest widths of 0.2, 0.3, and 0.4 in 10 flow intensities in the channel. The results of this study showed that by increasing hydraulic load, the flow intensity coefficient first increases and then decreases. Also, by increasing the relative length of the crest by 50%, the current intensity coefficient increases by 43% in the overflow. Increasing the relative width of the overflow crest by 50% increases the current intensity coefficient by 25% in the overflows. Also, an equation was presented to determine the maximum relative scour depth, and the correlation coefficient of the results of this equation with the laboratory results is about 0.90.
M. Salari, V. Rahdari, S. Maleki, R. Karami,
Volume 27, Issue 4 (12-2023)
Abstract
the countries of Iran and Afghanistan. A long period of drought has happened in this area by human interventions after 1999. The objective of current study is to predict the Hamoun wetland situation in scenarios with and without human intervention using the Markov model-automated cellular for 2019 and the next forty years. Land cover maps of the study area using satellite images for 1987 as a normal year, 1991 as a wet year, and 2019 as a year with human effects were prepared. Then, prediction model for 2019 were prepared using 1987 and 1991 cover layers in four scenarios, prediction models were prepared for the next forty years in normal, drought, and wet conditions. If the natural process of watering of Hamoun wetland continues, lower than 362735 hectares of wetland should become watering in 2019, while, according this year land cover map, less than 50000 hectares of wetland have water. Also, by continuation of the current trend and the effect of human activities in the 40-year models, 11230 hectares of the area will be watering, and if the natural process of the wetland continued using the model of 2019 this amount was equal to 373311 hectares. The results of the research show the completely different situation of the Hamoun wetland in the case of no human intervention in the watering of this wetland in 2019 and the model of the next forty years.
S. Abdollahi, A. Masjedi, M. Haidarnejad, A. Afros, M. Asadilor,
Volume 28, Issue 1 (5-2024)
Abstract
The use of structures has economic and safety advantages compared to other energy-consuming structures. In this research, to investigate the effect of the length of the sill of the flip bucket spillway on the scour downstream, experiments were conducted in a rectangular laboratory flume made of Plexiglas. The scouring downstream of the flip bucket spillway was investigated using a flip bucket spillway with four relative sill lengths and four threshold angles at four current intensities in the channel in this research. The results of this research showed that by the increase in the length of the sill in the flip bucket spillway, the energy consumption in the spillway increased and the scour depth downstream decreased. Also, increasing the relative length of the sill by 70% at the sill angle of 45 degrees, the scouring depth is reduced by about 88%. Also, a relationship was presented to determine the maximum depth of relative scour, and the correlation coefficient of the results obtained from this equation with the laboratory results is about 0.92.
