Showing 30 results for Vali
S. Vaseghi, M. Valinejad, M. Afyuni,
Volume 21, Issue 3 (Fall 2017)
Abstract
Nitrogen use efficiency is relatively low in irrigated rice fields because of rapid N losses from ammonia volatilization, the nitrification, surface runoff, and leaching in the soil-flood water system. Since the plant N represents the total N supply of all sources, plant N status will be a good indicator of N availability to crops at any given time. Leaf colour chart (LCC) is a simple portable diagnostic tool, to determine the timing of N top dressing. LCC was developed to increase the N use efficiency at irrigated rice fields. A field experiment was carried out to compare the effect of N split application and LCC on the grain yield and agronomic and recovery efficiency of Fajr variety in 2009. The experiment was conducted in a randomized complete block design with 12 treatments in 3 replications on Fajr cultivar. Twelve treatments included control treatments (without nitrogen fertilizer) and 45, 90, 135 kg N ha-1 for three times each and two treatments included LCC treatments 4 and 5. As a result, all treatments showed significant (p=0.05) grain yield increase in comparison to control. Increased yield was observed up to 135 kgN/ha (55.2%). Grain yield of LCC treatments was higher than split treatments. LCC treatment 5 had higher AE, RE, PE, PFP and IE than LCC 4 and fixed – 135 at the less N rate in all fields. Therefore, the results of different fertilizer treatments showed that the LCC treatment 5 with maximum grain yield, agronomic, physiological, internal and relative efficiency factors can be considered as the best management method for using nitrogen fertilizer and preventing from excess use of nitrogen fertilizer in Fajr cultivar.
A. Vali, F. Roustaei,
Volume 21, Issue 4 (Winter 2018)
Abstract
Wind erosion is the most important geomorphic process and the main cause of the landscape change in arid and semi-arid areas. This paper focuses on the Dust Storm Index (DSI) with the aim of monitoring wind erosion in Central Iran using meteorology data. The trend of standardized DSI and its three factors which are sever dust storm, moderate dust storm and local dust events were studied using Man-Kendal non-parametric test. It was found that wind erosion is accelerating in recent years. Compared to primary 20 years (1965-1985) DSI rate has been three times more than 30 years ago (1985-2014). The central and southern parts of Central Iran show the highest severity of wind erosion and the severity of DSI decreases by approaching the north. Therefore, considering the sensitivity of these areas, in addition to taking into account prevention programs, they should also be considered in regeneration and control programs.
F. Amiri, T. Tabatabaie, S. Valipour,
Volume 22, Issue 1 (Spring 2018)
Abstract
The purpose of this paper was to assess the groundwater quality near Qaemshahr landfill site using the Iran Water Quality Index for Groundwater Resources-Conventional Parameters (IRWQIGC). In this study, samples were taken from 11 wells with three replications in February 2015 and water quality was assessed by evaluating nitrate, fecal coliform, electrical conductivity (EC), pH, total hardness, sodium absorption ratio, biological oxygen demand, phosphate, chemical oxygen demand, and dissolved oxygen parameters with the standard measuring methods; also, the quality of ground water was determined using the IRWQIGC. Statistical description of the parameters was performed using the SPSS software. Spatial extension mapping parameters were drawn using geostatistics extension with the ArcGIS software. The results of water quality assessment revealed that 0.15% of the area was classified as bad, 98.85% as relatively poor, and 1% as middle in terms of quality. The results of spatial dispersion also revealed that water quality from the South to the North and North East was reduced. Evaluating the changes in water quality near landfill sites showed that 2149.56 square meters of total area had a relatively poor potential for the region’s groundwater recharge.
A. Jamal, A. Parvan, D. Valizadeh,
Volume 23, Issue 4 (Special Issue of Flood and Soil Erosion, Winter 2019)
Abstract
Today, the preparation of flood zoning maps is one of the basic and important issues in the study of development projects in the world; it is considered before any investment by the related organizations. In this paper, flood zoning was performed using the two-dimensional model HEC-RAS and GIS in order to assess the risk of the construction of a railway station near the bank of the Iranshahr River, in a range of 2500 meters. Two-dimensional hydraulic application could create a more accurate flow pattern in comparison to the one-dimensional model used in the previous studies, especially in the flood plain areas. In this paper, due to the important role of the topography of the area in ensuring the accuracy of the calculation, a Digital Elevation Model (DEM) was used with very high precision (about 2 meters), as obtained from aerial photos. The results of this study indicated the onrush of flood, depth and flow velocity in different return periods. Based on the comparison of water surface profiles in the floodplains with the return period of 100 and 25 years, the maximum difference between the water levels was 0.5 m, which seemed to be reasonable by considering the low slope of the studied area. The results of this paper, therefore, showed that the location of the railway station was in medium risk and the outskirt of floodplain.
M. Majedi Asl, S. Valizadeh,
Volume 23, Issue 4 (Special Issue of Flood and Soil Erosion, Winter 2019)
Abstract
Local scour around the foundation of marine and hydraulic structures is one of the most important factors in the instability and destruction of these structures. False prediction of scour depth around bridges has caused financial losses in plasticization and endangered many people's lives. Therefore, an accurate estimation of this complex phenomenon around the bridges is necessary. Also, since the formulas presented by different researchers relate to laboratory conditions, they are less true and less accurate in other situations. Recently, many researchers have tried to introduce new methods and models called soft calculations in predicting this phenomenon. In this research, 146 different laboratory data series (three different laboratory conditions) were analyzed using a backup vector machine to predict scour depth around the bridge head. These data are presented in the form of various combinations of input parameters which, respectively, represent thickness under the slippery layer, Reynolds number, critical velocity, Shields parameter, velocity Shear, average speed, flow depth, the average diameter of the particles and diameter of the bridge. The parameters in two different scenarios (the mode with dimension and mode) were introduced into the SVM network and the results of this machine were compared with those obtained from the experimental formulas and relations presented in this study. The results showed that in the first scenario, the combination of No. 5 with input parameters () and in the second scenario, the combination No. 5 with input parameters () for the test stage were selected as the best model. It was also concluded from the results that the scenario two (the state with dimension) in predicting the scour depth around the vertical single-pillar provided a more accurate estimate than the first scenario (barrier state). At the end, the sensitivity analysis was carried out on the parameters and the parameters D, U*, V were selected, respectively, as the most effective parameters
H. Ghorbani, A. Vali, H. Zarepour,
Volume 23, Issue 4 (winter 2020)
Abstract
Drought as a natural hazard is a gradual phenomenon, slowly affecting an area; it may last for many years and can have devastating effects on the natural environment and in human lives. Although drought forecasting plays an important role in the planning and management of water resource systems, the random nature of contributing factors contributing to the occurrence of and severity of droughts causes some difficulties in determination of the time when a drought begins or ends. The present research was planned to evaluate the capability of linear stochastic models, known as multiplicative Seasonal Autoregressive Integrated Moving Average (SARIMA) model, in the quantitative forecasting of drought in Isfahan province based on the Standardized Precipitation Index (SPI). To this end, the best SARIMA models were chosen for modelling the monthly rainfall data from 1990 to 2017 for every 10 synoptic stations in Isfahan province to forecast their monthly rainfall up to five years. The monthly time scale SPI values based on these predictions were used to assess the drought severity of different stations for the 2018- 2022 time period. The station results indicated a weak drought at the 2019- 2022 period for Isfahan, Kashan and Naeen, a severe drought in 2019 for Ardestan and Golpaygan, and a weak one in 2019 for the East of Isfahan, KabootarAbad and Shahreza stations. All other stations, except Golpayegan, Isfahan, Kashan and Naeen, faced a severe drought in 2018.
M. Majedi Asl, R. Daneshfaraz, S. Valizadeh,
Volume 24, Issue 2 (Summer 2020)
Abstract
Sand mining from rivers is one of the biggest concerns in the science today. Certain principles and rules for choosing the right place for mining materials and the amount of this mining are missing in the design codes. Therefore, mining of river materials from sites with less potential and near structures has been occasionally seen. In the present study, it has been attempted to reinforce the structure to control the impact of the mining of material, which results in the increased scour by changing the flow pattern around the structure. The experiments were carried out in two simple and armed modes, in sand bed with a grain size of 0.78 mm, with a length of 4.25 meters, inside a canal of 13 meters in length and 1.2 meters in width. The extent of scouring along the longitudinal and transverse directions in different times from the start to the scouring equilibrium was investigated for all substrates under sub-critical flow conditions (range 0.5-0.25). The results showed that the use of a cable-protected method in the upstream pit led to 29.6% reduction in the maximum scour depth at the front and 34% reduction in the back of the pier; also, in the downstream of the pit, it reduced the maximum scour depth by 15% at the front of the pier. Therefore, the cable arrangement used at the piers surface, according to the current research method, resulted in a significant reduction in the depth and extent of scouring in the pier group of the bridge.
A. Moghtaderi, E. Valizadegan,
Volume 25, Issue 2 (Summer 2021)
Abstract
In this study, the hydraulic characteristics of the flap gates are installed at the end of the trapezoidal channels were investigated by laboratory study. In the physical model, three trapezoidal channels and four gates with different weights were used (12 gates for three channels). Based on several experiments, equations for estimating of flow rate for each side slope (each channel) were developed using dimensional analysis. In this research, five forms of discharge-stage relationship were used to obtain relationships for each side slop to estimate flow rate, separately. The results show that none of the discharge-stage relationships forms as a single relationship for all flap gates in a certain channel are suitable for estimating discharge. But the first, second, and third forms of the discharge-stage relationship are very suitable for estimating the flow rate in a certain channel for a certain flap gate. In other words, for each gate with a specific weight, a separate (unique) relationship is obtained to estimate the flow rate in the form of the first to the third discharge-stage relationship in a certain channel. To estimate of flow rate by using the first form of the discharge-stage relationship, the maximum values of statistical parameters of RMSE, ME, and MARE, among all three channels, are 0.0001 m3/s, 0.00022 m3/s, and 0.22 percent, respectively. The values of all the above statistical parameters for the first, second, and third forms of the discharge-stage relationship are presented in the article.
H. Ghanbari, J. Mamizadeh, M. Valizadeh,
Volume 25, Issue 3 (Fall 2021)
Abstract
Water hammer is one of the unsteady flows in urban water distribution networks, which has been of great importance due to the damage caused to the pipeline and has always been of interest to researchers. In this study, the phenomenon of water hammer due to the sudden closure of the valve in the downstream end has been investigated in a laboratory and using a numerical model. In the laboratory section of the study, the effect of flow changes with control equipment and without control equipment on the maximum and minimum height of pressure wave head was investigated. The results showed that the proper performance of the surge tower pipe in reducing the maximum pressure wave as well as improving the negative pressures in the system. In a maximum discharge of 35.75 liters per minute, surge tower pipe reduced pressure wave head by a maximum of 70.40%. In a minimum discharge of 7.70 liters per minute, the surge tower pipe reduced the height of maximum pressure by 34.82%. Also, in minimum discharge, surge tower pipe has improved the minimum pressure wave head by more than 78%. AFT Impulse numerical model was used to analyze the water hammer. The results of the numerical model were examined in a benchmark problem using a characteristic method and its validity was confirmed. Simulation of laboratory model with numerical software showed that this software only predicts the first wave properly when water hammer produces negative pressures, but in the next cycles it does not show the depreciation rate of the pressure wave, properly.
A.s. Hosseini Khezrabad, A.a. Vali, A.h. Halabian, M.h. Mokhtari,
Volume 27, Issue 4 (Winter 2023)
Abstract
Desertification is one of the most serious ecological environmental problems in the arid regions. Quantitative assessment of the desertification process is important for the prevention and control of desertification. In this research, the IMDPA model was used to evaluate the quantitative and qualitative desertification situation in the northwest of Yazd. Three criteria of soil, vegetation, and wind erosion were considered in this model. Several indicators were defined for each criterion with a weight of 0 (low) to 4 (very severe). The geometric mean of all three criteria was used to prepare a map of sensitive areas to desertification in ArcGIS. The results indicated that more than 92% of the research area was in the extreme class of desertification, and only the dunes work unit was in a very intense class. Finally, the whole of the research area with a final score of 3.04 was placed in the extreme class of desertification intensity. Also, the soil criterion with the highest weight score of 3.26 has had the greatest impact on the desertification of the northwest region of Yazd. Therefore, it is necessary to implement remedial and revitalization operations in this region according to the expansion of the phenomenon of desertification and the high influence of the soil criteria. The results of the research showed the intensity of desertification, the potential, and the sensitivity of the region to the phenomenon of desertification can be referred to as a departure from the natural functioning of the system.
