مجله پژوهش آب ایران
پیاپی 50 (پاییز 1402)

In recent decades, the amount of runoff has decreased significantly in a few regions of the world. Human activities and climate change are the two main factors in runoff changing. Accordingly, it is very important to analyze the influencing factors and quantify their impact on the runoff. In this research, the analysis of the process of gradual and sudden changes in the QezalOzen River runoff at the Yesaul hydrometric station in Kurdistan province was carried out using the linear regression method and Pettit's test. The results showed that the runoff time series in the upstream watershed of Yesaul hydrometric station has a decreasing trend and the breaking point of the runoff time series is 1998. According to this, the runoff time series was divided into the base period and the evaluation period. Runoff simulation was done using SWAT model. After entering input data of the watershed in the SWAT model, the model was implemented between 1987 and 2010. From 1987 to 1993 is before the change point. Based on this, syear 1987 was used as warmup, 1988 to 1991 was used for calibration, and years 1992 and 1993 were used to validate the model. SUFI-2 algorithm was used in SWATCUP software package to calibrate the model. Since the number of the parameters in SWAT model is large, before calibration, the sensitivity analysis was done and the sensitive parameters were determined. Examining the results of calibration and validation of the model in the base period showed that the SWAT model has a good performance in simulating the runoff in Yesaul hydrometric station. Also, the results of the study showed that the impacts of climate change (76%) in reduction of runoff during the evaluation period is much higher than the impact of human activities (24%). In general, the current research states the necessity of taking necessary measures to adapt to climate change and create guidelines for human activities for sustainable access to water resources.

One of the most critical problems in using bottom intake is the accumulation of sediments on the garbage catch network and immediately after this network. Also, sediments whose size is smaller than the distance between the bars pass through the bars and settle in the intake channel. Accumulation of sediments on the garbage collection network and in the water intake channel, as well as sediments getting stuck in the space of the garbage collection network, will reduce the efficiency and increase the operating costs of this water collection system. To solve these problems, replacing the mesh floor with a porous medium is proposed. Although the latter method has limitations, its numerous and significant advantages confirm its replacement. This type of intake is called a porous bottom intake. In the simplest case, a trench is dug at the river's bottom to build it. This trench is filled with a material with appropriate granularity, and water is directed to this trench through an end structure to the transmission line or diversion channel. Due to the greater use of this intake in the headwaters of rivers with steep slopes and the lack of access to concrete materials in such conditions, this type of intake can be technically and economically efficient. This research mainly compares the hydraulic performance of one- and three-dimensional floor intakes. For this purpose, two one-sided and three-sided water intake samples have been tested in different hydraulic conditions. Also, the effect of the main channel slope and the granularity of the materials of the porous media around the intake has been investigated. In the first part, the performance results of the three-dimensional water intake, and in the second part, the hydraulic performance of the corresponding one-dimensional model has been examined. The performance results of these two intake types have been compared in the third part. Also, in the final part, their discharge coefficient is compared.

This research experiment was carried out in a laboratory flume with a length, width, and height of 11, 0.5, and 0.5, respectively. In this research, two models of one and three-dimensional intakes were tested. Three different granulations of particles with an average diameter of 1.94, 2.5, and 4.13 mm were used for the porous part. Also, to investigate the effect of the slope of the main channel, according to the ability to change the slope of the laboratory flume, tests were performed for two slopes of 1 and 1.67%.

The results show that the changes in the water intake discharge compared to the total discharge are increasing at the beginning with a higher slope and then with a gentle slope as a power function. Although it is expected that with the increase in the size of the materials, the amount of water intake will be higher, in the sample used in this research, due to the distribution of granularity, materials with an average diameter of 2.5 mm have more water passage than the total flow. The results show that the percentage of membrane discharge from the 2.5 mm granulation is higher than the other two. The slope effect is minimal in all three gradings, and no significant difference is seen from the slope effect. The changes in the percentage of water passing about the total flow are reduced exponentially. Due to the specific capacity of porous media, a higher percentage passes through the intake at low flow rates and decreases with increasing flow rates. In this model, for the slope of 1% of the main channel, the highest flow rate from the porous intake is related to the material size of 2.5 mm and the lowest for the material with a granularity of 1.94 mm. Like the M1 model, the one-sided intake has no noticeable slope effect. The ratio of discharges is between 2 and 10% for a 1% slope and between 2 and 8% for a 1.67% slope. On average, the flow through the M1 model is 72% higher than the M2 model. On average, the ratio of internal flow rate to total flow rate for the M1 model is 6% higher than the M2 model. The difference in this ratio is more in low flow rates and is about 21%, and with the increase in the flow rate of the main channel, it gradually decreases and reaches about 2%.The results show that the discharge coefficient of the single-sided water intake is higher than the three-sided water intake. The average value of the discharge coefficient of the single-sided intake is about 70% higher than that of the three-sided intake.

Water balance looks like a simple function, but its estimation at the watershed level is a complex process. For this purpose, water balance models could be a useful tool for simulating water balance components. The aim of this study was to simulate the surface water balance of the Karun 4 watershed using a model with minimum input data, because one of the problems in mountainous areas is lack of data. Many water balance models have been used in Karun watershed. Therefore, the Exp-Hydro model, which has not been used in Iran so far and has a simple structure and minimum input data, was selected. Exp-Hydro is one of the watershed-scale daily hydrological models that make use of daily data including precipitation, air temperature and potential evapotranspiration as input and simulates the daily streamflow at the watershed outlet. Due to its simple structure in this study, the open-source model, written in Python was used to simulate the daily runoff of the Karun 4 watershed.

In this study, the spatially lumped version of the Exp-Hydro model was used to simulate daily runoff. The script code of the model was written in Python. Python software, NumPy, SciPy, and Matplotlib library functions were installed to run this model. The input data of the model were prepared in separate files in text format. Then the results of Exp-Hydro model were compared with a daily water balance model that was developed in this study. This model was prepared in Excel software. The statistical period of this study was from 2000 to 2020, where two-thirds of the data were used for the calibration period and one-third for the validation period. The WHAT software and recursive digital filter method were used to separate the baseflow from the observed daily flow data. The Exp-Hydro model was calibrated automatically using PSO optimization algorithm and the daily water balance model that developed in this study was calibrated using Goal Seek method. The efficiency of the models were evaluated in this study by means of Kling Gupta criteria (KGE), Nash-Sutcliffe efficiency coefficient (NSE), Correlation coefficient (R), Root Mean Square Error (RMSE) and Mean Absolute Error (MAE).

In the separation process of the base flow values from the total flow of Armand hydrometric station, was done in such a way that in the minimum flows, the separated flow rate corresponds to the minimum values, which in this case, the values of the two constant parameters of the filter parameter and base flow index (ratio of baseflow to the total flow) was chosen as 0.9 and 0.36, respectively. Evaluation of the developed daily water balance model's performance using the KGE, NSE, R, RMSE and MAE showed that these objective functions were 0.76, 0.69, 0.83, 0.25, and 0.11 respectively during the calibration and 0.76, 0.62, 0.85, 0.19, and 0.09 respectively during the validation period. This means the developed daily water balance model in this study has produced good and satisfactory outputs. Also, the evaluation of Exp-Hydro model's performance using the KGE, NSE, R, RMSE and MAE showed that these objective functions were 0.69, 0.37, 0.69, 0.35, and 0.14 respectively during the calibration and 0.6, 0.19, 0.71, 0.28, and 0.11 respectively during the validation period. This means the developed daily water balance model in this study has produced good and satisfactory outputs. This means the Exp-Hydro model has an intermediate performance according to the KGE coefficient in both calibration and validation periods. In addition, the developed daily water balance model in this study estimated the low flows with higher accuracy and both models had underestimated regarding flood flows. Sensitivity analysis of Exp-Hydro model was done manually by changing each parameter of the model and comparing the changes between observation and simulation runoff hydrographs, and the value of efficiency coefficients was also controlled. In this analysis, it was found that since f is the parameter that controls the reduction of runoff depending on the reserve, this parameter has an inverse relationship with simulation runoff value; So that by decreasing the f value, the simulation runoff values increase and become more than the observation runoff values. Also, this parameter was the most sensitive parameter in the Exp-Hydro model. In the developed daily water balance model in this study, m in calculating maximum runoff generated in the catchment bucket using the Reservoir performance exponential function and e in calculating snow melt were the most sensitive parameters. These parameters were the most sensitive parameter in this model; so that by reducing their values, the simulated runoff values of the model decrease and become lower than the observed runoff values. In general, the performance of the developed daily water balance model in this study was better than Exp-Hydro model.

Dams are one of the fundamental infrastructures in every country, which have been used and exploited for purposes such as water storage, flood prevention, and energy production. In the design and construction of large dams, various safety coefficients are always applied based on guidelines and codes, to reduce the risk of dam failure. However, dams are always subject to failure and the probability of dam failure cannot be reduced to zero only by considering these coefficients. The dam's failure can be based on various factors, including water leakage, cavitation (internal erosion), overpass due to insufficient overflow capacity, and liquefaction caused by earthquakes. Due to the amount of water stored in the reservoir of the dams and sometimes their proximity to the residential areas, the failure of the dams can lead to many human and financial losses. Dam failure mainly causes the transfer of bed sediments and morphological changes downstream. According to the presented statistics, the loss of lives in the failure of concrete dams (immediate dam failure) is twice of gravel dams (gradual failure). The main cause of this issue is the different nature and mechanism of dam failure based on its type, such that concrete dam failure is explosive-sudden and earth dam failure is gradual. Therefore, the type of dam break has been considered one of the effective parameters in evaluating bed sediment transport and bed morphology.

In this research, experimental and numerical studies have been carried out in order to investigate the phenomenon of bed sediment transport under two types of instantaneous and gradual dam failure.The experimental model has been implemented in the flume of Babol University Hydraulic Research Center and the instantaneous failure of the dam has been modeled by considering the sediment layer in the dam reservoir and downstream. Also, in these experiments, three types of sediment materials (sand d50=4mm, coarse sand d50=10mm, gravel d50=20mm) have been used as effective variables in bed morphology. Numerical modeling has been implemented in ANSYS software using the Fluent model. In the process of numerical modeling, the experimental models are simulated and two variables of the meshing size and the turbulence model are studied. After the sensitivity measurement of the numerical model and the model calibration, the performance of the numerical model is examined and the error rate of the numerical model is compared to the experimental results. Finally, scenarios have been defined for modeling the phenomenon of sediment transport under instantaneous and gradual dam breaks.

Experimental modeling has been carried out in the laboratory flume of the Hydraulic Research Center of Babol University, which has a flume of 10 meters in length, width and height of 0.5 meters. In order to perform numerical modeling, Fluent is used and it is calibrated based on two parameters of the mesh size (0.5, 1, 2 cm) and the turbulence model ((k-ɛ / Standard) and (k-ɛ / RNG)). In addition, the performance of the numerical model has been evaluated based on the results of the experimental model. Experimental modeling has been done based on two instantaneous dam failure models (models A1, B1) with the same thickness of the sediment layer and with different types of sediment materials (types A, B). The results show that in the area of the dam failure (around the position of the opening gate (level 1.5 meters long)) in both models, there was first a decrease in the sediment layer and then an increase in the sediment layer. It is also clear that in model A1, the amount of reduction and increase in the thickness of the sediment layer around the failure zone has greater values than in model B1.Based on the results of the sensitivity analysis of the numerical model with respect to the meshing size, it has been found that the 1 cm meshing has a modeling error of 2.41% compared to the laboratory model. In addition, the results of the sensitivity analysis of the numerical model with respect to turbulence models ( (k-ɛ / Standard) and (k-ɛ / RNG)) showed that the k-ɛ / Standard turbulence model had a modeling error of 2.75% and has been performed better. By examining the results of the numerical modeling, it has been found that the average modeling error is less than 5% (CA1 model has an error of 2.75%, CB1 model has a modeling error of 4.71%), which indicates a high accuracy of the numerical model.In order to numerically model the gradual dam failure in the Fluent model, a movable gate has been used. For this purpose, the movable gate, which has the boundary condition of an impermeable wall, is placed in front of the water reservoir of the dam, and based on passaging time, it leads to an upward movement. In the Fluent model, the moving mesh technique is used to implement the movement of the gate.The results show that the rate of bed sediment transfer and thus the reduction of the thickness of the sediment layer in the gradual failure of the dam had greater values than the instantaneous failure under the same modeling conditions. In other words, the thickness of the sediment layer under the same modeling conditions in Gradual failure has been reduced more than in instantaneous failure. In the gradual dam failure with the movement of the gate, the simulation has been done gradually with the passage of time, so the duration of water discharge as well as the interactions between water and sediment particles is more than the instantaneous failure.By evaluating the results of numerical models, it has been determined that the size of sediment particles (type of sediment material) has been an effective parameter in the changes of bed morphology in both instantaneous and gradual dam failures. The percentage of sediment layer changes in conditions of instantaneous failure compared to gradual failure for gravel materials (Type A material) has been equivalent to 7.47%, for sand materials (Type B material) equivalent to 19.35%, and for intermediate materials (Type C material) equivalent to 11.52%.

Rivers are always one of the important natural resources in meeting the needs and development of human society. Living on the marginal of rivers are associated with risks and problems such as flooding and displacement damages. Floods are an important source of water in arid regions, and alluvial aquifers are recharged by infiltration of seasonal stream flow of rivers. there are many factors affecting floods over the watershed, and it is almost impossible to control and measure all these factors. Therefore, in order to predict floods, the conditions and characteristics must be simulated using hydrological models. River bed usually do not have a permanent flow in dry areas, therefore the flooding water from upstream to lower reaches in the waterway bed is faced with losses due to infiltration and filling of depressions. This situation is more complicated in dry areas, because it is not possible to accurately estimate the amounts of losses in these intervals, and therefore, usually only if there are hydrometric stations on the upstream and downstream, the amounts of losses are calculated in the interval between them. The greatest flood losses, especially decreasing of the peak discharge and its volume, occur when the flood is transferred from the waterways with alluvial beds to the downstream. The Khoshk river that passes through the middle part of Shiraz city has such conditions that flooding every year and remains a lot of damage. Therefore, due to the importance of flood forecasting to reduce downstream risks, it has been selected in this research.This river, which is located in Fars province, is a seasonal river that originate from the west to northwest heights of Shiraz city and after passing through the middle of the city, flows into Maharlu Lake. This river is a combination of two eastern and western branches, the eastern branch was named Nahr-e Aazam and the western one was named Chenarsukhteh. The Khoshk river, as one of the sub basins of the Maharlu Lake, has an area of about 900 square kilometers. Two branches inter shiraz city independently, so that, Nahr-e Aazam branch is 11 km long and 0.00525 percent slope and Chenarsukhteh branch is 13 km long and 0.0153 percent slope in Shiraz city, and then they connect to each other and form the Khoshk river. The Khoshk river passes through the city of Shiraz with a distance of 33.5 km and a slope of 0.00556 percent, and then inter to the Maharlu lake. The course of this river inside the city of Shiraz is in the form of an independent canal and all its banks are separated by a wall. MKE-11, which is a one-dimensional mathematical modeling software, is used to simulate flood routing in such rivers. Flood routing has done hydraulically by solving the Saint-Venant equations in this model. In addition, the solution of Saint-Venant's equations is done by using the finite difference method through the 6-point Abbott grid and solving the continuity and motion equations simultaneously by using the dynamic wave method. This model is adjusted using Manning's coefficient. In the hydrodynamic module, first the Saint-Venant equations were written using the finite difference scheme, and then the equations were analyzed using a grid of points in different places and times. In order to simulate the flow in the Khoshk river, the geometric information of 470 cross sections was used. Manning's coefficient for the branches of Nahr-e Aazam, Chenarsukhteh, and Khoshk river are estimated at 0.024, 0.048, and 0.035, respectively. The accuracy of the values was determined by calibration. Model calibration has been done using Manning's coefficient and observed flood gauge curves with a return period of 100 years, based on the comparison of simulated gauge curves. The measurement curves were compared with the Root Mean Square Error (RMSE). This model has also been recalibrated for leakage coefficient in Nahr-e Aazam, Chenarsukhteh and Iqbal Abad stations. The best value that matched the field characteristics was 10-5 (l/s). The recalibration of the leakage coefficient led to the improvement of the results and the model is accurate enough to simulate the seasonal river. In this research, the flood routing in the Shiraz Khoshk river was carried out and the transfer loss was calculated. Recalibration of the model for the leakage coefficient led to an increase in the agreement between the simulated curves of the gauge and the observed curves. The leakage coefficient is equal to 10-5 (l/s), which was the most consistent. The high slope of the Chenarsukhteh branch compared to the Nahr-e Aazam branch has led to a significant decrease in volume loss in this river branch. Increasing the return period leads to an increase in the volume of transmission loss. It should be noted that the volume of transmission drops in the return period of 25, 50 and 100 years is more than one million cubic meters, which can be a suitable source for feeding the underground water of the region. The percentage of penetration increases with the reduction of the return period; In such a way that in the return period of 5 years 20 percent of the volume of flood penetrates into the Khoshk river.

Due to the increase in population, food needs, and decreasing fertile agricultural lands without salinity problems, the requirement for irrigation with good quality water will become more valuable every day. In many developing countries, population growth, climate change, lack of land, and improper management of water and soil have caused a decrease in soil fertility and, as a result, limited supply of essential plant nutrients. Considering that Iran is located in the region with hot and dry weather conditions and there are not enough sources of water with good quality in the country and also the soils are mostly salty and calcareous, it is obvious that solutions should be considered to improve the quality of water. Considering the limited water for planting crops, using unconventional waters like salt water, is one of the most suitable ways to increase productivity from agricultural land. One of the methods is the use of magnetic water technology. The purpose of this research is to investigate the effect of using magnetized saline water on the yield and yield components of maize (SC 704) plants by using a drip irrigation system.

The experiment was conducted as a factorial in the form of a randomized complete block design with three replications in the crop year 2021-2022 in Babolsar City with the coordinates of 59 degrees and 39 minutes of latitude (oN) and 36 degrees and 43 minutes of longitude (oE) at an altitude of -21 meters above the surface of the open seas. According to long-term data and based on Dumarten's climate classification, the region has a humid climate. According to long-term statistical data of 30 years, the average annual rainfall of the region is 891 mm and the average annual air temperature is 17.5 degrees Celsius. Irrigation water salinity treatments included 0.6 (S1), 3 (S2), and 6 dS/m (S3) under conditions of application of magnetic field (I1) and without magnetic field (I2). Magnetization of irrigation water was created by passing water through a permanent magnet with a magnetic field intensity of 0.3 Tesla. The working method was that in magnetized water treatments, the device for creating a magnetic field was installed on the pipeline and the water that was considered for irrigation of these treatments passed through this conduit. Irrigation frequency of 3 days and considering the efficiency of 90%, the irrigation demand was determined. Irrigation amounts in each treatment were applied by volume meter. At the end of the experiment period, the characteristics of fresh and dry weight of the plant, number of seeds, weight of 1000 seeds, biological yield and seed yield per lysimeter were measured. SAS software was used for the statistical analysis of the data and comparison of means was done by Duncan's test method.

Salinity stress is one of the factors limiting the vegetative and reproductive growth of most plants and it is a factor that affects the metabolism and morphology of the plant. Due to the lack of quality water suitable for use in the agricultural sector, it is necessary to use non-conventional water. In this research, irrigation with different salinities under the effect of magnetic field on maize yield and yield components was investigated. The results showed that the effect of irrigation type and water salinity on plant wet weight, plant dry weight, number of seeds per cob, 1000 seed weight, biological yield, and grain yield were significant. The comparison results of the average of water salinity treatments showed that there was a significant difference between all the salinity treatments of 0.6, 3 and 6 deci-Siemens/m. Increasing water salinity decreased biomass weight and green cover in maize plants. On average, irrigation with magnetized saline water caused increase of 16.3% in plant wet weight, 21.2% in plant dry weight, 17.2% in number of seeds per cob, 12.9% in 1000 seed weight,13.73% in grain yield and 22.13% increase in the biological yield of maize compared to non-magnetic water. Also, the maize yield components decreased with increasing water salinity. In general, it can be concluded that magnetic water technology can be used to improve plant performance. It is suggested to use magnetic water technology to control salinity in the lands where non-conventional water is continuously used for irrigation, according to the type of plant and the tolerance threshold of the plant to salinity.

Lack of water resources is one of the important issues in the world. seepage losses from the canals are the most important part of losses during agricultural water conveyance. Considering the share of agriculture in the consumption of water resources, the estimation of water losses from the body of earthen canals is one of the major issues in the design and management of irrigation and drainage networks. According to the researches, unlined canals lose 50% of their transfer water through leakage. In addition to water losses due to seepage, one of the main reasons for the importance of checking the amount of leakage is the reduction of the quality of the land and soil around the water conveyance and distribution canals and the threat to the environment of the region. Average losses of water from irrigation canals in Iran, are on around 60%. The methods of estimating seepage losses from the earthen canals include the field method, empirical relationships, and theoretical methods. There are many empirical relationships in this field, but experience has shown that the coefficients of these relationships are different according to the conditions of each region and should be calibrated for local conditions (Rostamian and Abedi Kopaee, 2014). Mutema and Dhavu, (2021) stated that the characteristics of the canal such as wetted perimeter and wetted area, have a significant effect on water losses. The purpose of this research is to investigate the regression relationship between the leakage flow from earthen canals with hydraulic characteristics and flow.

In this study, using the information of the study conducted in the east of the Zayandeh Rood basin, the non-linear regression relationship between the seepage (s) and the inflow rate (Q), wetted perimeter, hydraulic radius (R), and hydraulic depth (D) was investigated. In order to derive regression relationships, 70% of the data related to two series of measurements in 9 canals were used. Validation of regression relationships was done using 30% of the data, which is related to the measurement in the third time and related to the same canals. The data were obtained from the direct measurement of the inlet and outlet flow rates and the geometric and hydraulic characteristics of the earthen canals, such as the shape and dimensions of the canal section and the water depth. In this research, the relative value of root means square error, RRMSE, mean absolute error, MAE, and mean error, MBE, were used to evaluate the accuracy of the relations extracted from the indices. The difference between the value calculated in the validation step obtained with each of the regression relations, with the measured values, is shown using RRMSE and MAE statistical indices. The smaller the values of these two statistics are, the more accurate the regression relationship will be in estimating the seepage from the canals under study. Also, the MBE index will be a positive or negative value, which will be an indicator of underestimation or overestimation of seepage losses, respectively.

The results showed that all three regression relationships the seepage (s) and the inflow rate (Q), wetted perimeter, hydraulic radius (R), had better accuracy than the best empirical relationship used in the study area (the Ingham equation). It should be noted that the above relations are probably valid for the flow ranges between 30 and 390 liters per second (values measured in the research of Salemi and Sepaskhah (2015) and in using these relations in this area for flow rates outside of this range, should be cautious. The values of the mentioned indices, RRMSE, MAE and MBE, related to the regression relationship between the amount of seepage and the inflow rate, were 0.1954, 0.0082, and 0.0058, respectively and in the regression relationship between the amount of seepage and the wetted perimeter, respectively, it is equal to 0.2113. 0.0091, 0.0058 were obtained. Also, according to the positive values of the MBE, it can be concluded that in all the extracted relationships, the average of the estimated data showed a lower estimate than the observed values. Comparing the results of this research with Heidarizadeh and Salemi's (2013) shows that except for the regression relation related to hydraulic depth regression relations have better accuracy than the best experimental equations that studied by them, that is, the Ingham relation. Also, compared to Vedernikov's theoretical method, the accuracy of the estimation of the mentioned regression relationships is lower, but the difference in the statistical indicators is not significant. Therefore, according to the previous studies and comparing it with the regression relationships obtained in this research, it is recommended that in the case of using empirical relationships to estimate the amount of leakage losses from earthen canals in this region, these relationships should be used instead of the empirical relationships. In this regard, Salmasi and Abraham (2020) in a research also dealt with the prediction of leakage from earthen canals using the finite element method as well as multivariable nonlinear regression, and their results also showed the high accuracy of the resulting regression relationships. Water crisis and its management and planning require detailed design of all components of water distribution and consumption systems. Assessing and quantifying leakage loss from irrigation canals is high important for the protection and management of water resources, and specifying the intensity of leakage loss, and for the evaluation of the potential benefits of leakage reduction techniques and technologies. In this research, the non-linear regression relationship between the seepage and some hydraulic characteristics of flow in irrigation canals, by using the information obtained from the studies of the seepage losses of earthen canals in the eastern region of Zayandeh Rood basin, were extracted to estimate these losses. The results of this research have shown the appropriate accuracy of regression relationships compared to other experimental equations used in the study area. Therefore, it is recommended to use the obtained regression relationships to estimate the loss of water leakage in this area. Of course, in using these relationships, it is better to control the inflow rate range and then use these relationships. In addition, in order to complete the studies, it is recommended to carry out similar studies on the channels of this region with a larger inflow rate.

Different types of energy dissipators are used to reduce the excess kinetic flow energy downstream of the spillways. The flow characteristics of submerged jumps differ significantly from those of free jumps. It was observed that the mixing of the flow jet decreases with the increase in the submergence of hydraulic jumps. This leads to reduced energy dissipation compared to free jumps. Pressure fluctuations in energy-dissipator structures are caused by the fluctuating nature of hydraulic jumps, which are caused by strong eddies and water-air mixing. Therefore, the identification and measurement of hydrodynamic pressures on the bottom of stilling basins play a significant role in the design of the thickness of the bottom slab and the determination of effective forces. Most of the research have been carried out in the field of hydrodynamic pressures of free hydraulic jumps in stilling basins with rough bed downstream of sluice gates. However, few studies are found in the literature regarding the effect of chute blocks and the end sill of the stilling basin on the bottom pressure fluctuations downstream of the spillways for different values of the initial Froude number and the submergence ratio in hydraulic jumps. This research aims to understand the mechanism of pressure fluctuations and determine the coefficient of pressure fluctuations intensity (C'P) of hydraulic jump at the bottom of USBR Type I (smooth bed) and Type II stilling basins, including chute blocks and end sill, at the downstream of the spillway.In this paper, the C'P coefficient on the bottom of USBR stilling basins was evaluated based on the experimental data. Several experiments were carried out in the hydraulic laboratory flume of the University of Tabriz to collect data. The geometric dimensions of an Ogee spillway and stilling basins were designed based on USBR criteria. Based on this, the length of Type I (LI) and Type II (LII) basins for the maximum flow discharge (Qmax) was calculated as 200 and 125 cm, respectively. Experiments were performed at different flow discharges varying ratios of submergence (S=Yt/Y2) equal to 1 (for free jump), 1.05, 1.1, 1.2, 1.3, and 1.4, respectively. The values of initial Froude numbers (Fr1) for different flow discharges were calculated in the range of 7.12 to 9.46. Therefore, in the present research, the range of relatively high values of Fr1 was investigated. Pressure transducers were used to measure fluctuating pressure data, which could record instantaneous pressure values at different times and provide the time series of pressure at for each pressure taps. The pressure transducers were calibrated for the pressure load range of ‒100 to +100 cm, and their nominal measurement accuracy is ±0.5%. The data acquisition frequency of the pressure transducers was 20 Hz, and the duration of data collection was 90 seconds for each pressure taps in each experiment. The number of pressure taps was equal to 25 points. Each pressure tap was connected to the corresponding pressure sensor using a hose with a diameter of 3 mm.The results showed that the maximum values of the CʹP coefficient occur in the initial zone of basins. In free jumps, CʹPmax values in the basinI were located in the range of 15 ≤ ΓX ≤ 20, and in the basinII in the range of ΓX ≤ 15. The variation trend of free jumps showed that in the zone of ΓX ≤ 10 of the basinI and basinII, CʹP coefficient values increase by 49% and 36% on average, respectively, by decreasing the Fr1 parameter. The rate of increase in CʹP coefficient values in free jumps with the reduction of the Fr1 parameter in the zone of ΓX > 10 in basinII was somewhat higher than basinI. In the upstream location of submerged jumps, the CʹP coefficient increased as the Fr1 parameter decreased. The increase of the CʹP coefficient with the decline of the Fr1 parameter in submerged jumps for the upstream zone of basinI and basinII was calculated to be equal to 7 and 4.8 percent, respectively. In the area of ΓX > 10 in the basinII, depending on the degree of submergence of the jump, the values of the coefficient CʹP ranged from 62 to 77% with the decrease of the Fr1 parameter. The variations of the CʹP coefficient in the downstream area of basinI were somewhat similar to basinII. The values of the CʹP coefficient in the upstream zone of the basins for higher Froude numbers were higher in submerged jumps than in free jumps. It seems that the turbulence intensity of submerged jumps in this zone was higher than free jumps. The results showed that the position of CʹPmax values of free jumps inside the basins is located in the zone of ΓXmax < 22 and ΓXmax < 16, respectively. The mean values of CʹPmax in free jumps of the basinI and basinII were achieved around 0.039 and 0.062, respectively. The reduction of CʹPmax in basinII compared to basinI in free jumps is 38% on average. The values of the CʹPmax coefficient decreased with the increase of Fr1 in free and submerged jumps. As the submergence ratio (S) increased, CʹPmax values decreased in different Froude numbers (Fr1). CʹPmax for the minimum Froude numbers had higher values in free jumps compared to submerged jumps.

The agricultural sector is the main consumer of water resources in our country. To increase irrigation efficiency and optimal use of water resources in arid and semi-arid areas, it is considered to use super absorbent materials with very high water absorption ability. Diatomite is a material with super-absorbing properties that is receiving attention today, and it is a mineral that is abundantly found in South Khorasan. This mineral, which is the sedimented remains of a marine fossil, has many microscopic holes and therefore has the necessary potential to solve water shortages and deal with drought stress. Considering these interesting features of this material and considering the location of South Khorasan province in a dry region with a lack of moisture and the worsening of this problem due to the continuous drought of recent years, the main purpose of this research is to investigate the use of diatomaceous in Esfazar Birjand region to improve agricultural soils with big texture it is.

In order to investigate the effect of diatomite on the water absorption and storage capacity in the soil, the soil sample with sandy texture was first prepared from Bidokht village of Birjand. Different amounts (0, 10, 20, 40, 60, and 80 grams) of small diatomaceous earth with different particle sizes (0 to 2, 2.36 to 4.75, 4.75 to 12.5, and 12.5 to 19 mm) were added to one kilogram pots of soil. The experiments were conducted in a completely randomized design with three replications. The number of investigated treatments is 24 and in 3 replications. For the size of diatomite particles larger than 2 mm, only the treatment of 40 g/kg soil with two replications was used. In this research, besides raw diatomite, calcined diatomite was also used in the treatment of 20 g/kg soil. The process of calcining raw diatomite without pyrolysis agent was carried out at 900 degrees celsius for four hours in the mineral processing laboratory of Birjand University. In all treatments, diatomite particles were completely mixed with one kilogram of dry soil, and then the soil moisture was brought to the agricultural capacity (18%). Weighing the pots once every ten days and the amount of moisture reduction for different treatments. It was measured and based on the available moisture, irrigation was done until the moisture reached the agricultural capacity. For some time, the pots were saturated with water based on the percentage of saturated moisture, and the gravity moisture content of each treatment (amount of water removed) was measured. After 4 months, the effect of adding raw diatomite and calcine on soil water absorption capacity and water retention capacity was measured.

Based on the results of this research, adding diatomaceous to the soil had a significant effect on increasing the saturated moisture content of the soil. So that the highest moisture content of the soil by adding 80 grams of diatomite. For every 10 grams of raw diatomite added to one kilogram of soil under investigation, 1.25% was added to the saturated moisture content of the soil. Also, it was obtained it was found that the use of calcined diatomite increased the water absorption capacity of the soil by about 20% more than raw diatomite. It was also found that by adding diatomite particles larger than 4.75 mm, the water absorption capacity of the soil increases significantly. These results determined that crushing diatomite actually causes the loss of a major part of its internal empty space that has the capacity to absorb water. This happens with the further crushing of diatomaceous. Therefore, it is recommended to use coarse diatomite particles with an approximate size of 5 to 12 mm or 12 to 20 mm to improve agricultural soils with low water absorption capacity. In relation to the water holding capacity, the results showed that for every 10 g/kg of diatomaceous earth added to the examined soil, 0.6% is added to the 48-hour moisture level of the soil. The use of calcined diatomite did not show any effect on the water holding capacity, but the use of coarser raw diatomite particles increased the water holding capacity of the soil. In total, the results of this research showed that the use of raw diatomite particles with a size of 4.75-19 mm has the most effective for increasing the water absorption and retention capacity of agricultural soils.

Climate change phenomenon and warming earth as well as drought, have been reducing water sources in the world wide at the last decades, especially in arid, semi-arid regions. On the other hand, soil qualities factors including organic matter and fertility, in addition to soil salinity are the most critical issues in agricultural management and environmental conservation. Applying chemical fertilizers is one of the management methods in arid and semi-arid regions to amends decreasing water resources and supply required plant nutrients in recent decades. Although using fertilizers cause to increase production and crop yields, but meantime this management way leads to destroying the soil structures. Soil nitrate pollution is the most important challenge in agriculture and environment. The numerical models were used in predicting element concentrations under various climates, management methods, and study conditions (laboratory or field,). Estimated soil hydraulic and solute transport parameters are the most important part of applying numerical models to evaluate trends in soil element concentration changes under management methods. Hence, in this research soil hydraulic and solute transport parameters was predicated under center pivot irrigation using particle swarm optimization algorithm and the obtained results of optimization in soil water and nitrate transport along soil profile was used to survey soil pollution on the farm under four-year- alfalfa cultivation. In this study a farm with 3 hectares under center-pivot irrigation and four- year- alfalfa cultivation was chosen in an arid and semi-arid region. In the first step, a profile on the farm was drilled and sampling were done at the two depths (0-40 cm and 40-100 cm), finally soil physical-chemical properties were measured. In the second step, the particle swarm optimization algorithm linked to the HYDRUS model and parameters of soil water and nitrate transport process was predicated under management conditions. In the final step, the trend of soil water content, ammonium, and nitrate concentration changes were evaluated using the HYDRUS-PSO with the statistical indices (NSE and RMSE). The obtained results of the study soil profile showed that heterogeneous condition dominates the soil profile. Along the soil profile gravity of soil and sand content was changed in the specific. The results of the HYDRUS-PSO model were indicated different values of soil hydraulic and solute transport parameters in both studied two depths. The two indices of NSE and RMSE, were used to evaluate the calibration and validation of the HYDRUS-PSO model. The obtained results show that the HYDEUS-PSO model simulated soil water flow with NSE equal to 0.89 and RMSE equal to 0.001, ammonium transport with NSE equal to 0.98 and RMSE equal to 0.001 and nitrate transport with NSE equal to 0.94 and RMSE equal to 0.035 in the surface soil. Also, the evaluated model in the subsurface soil indicated that the HYDRUS-PSO model reasonably predicated soil water, ammonium and nitrate variation with NSE equal to 0.94, 0.96 and 0.97 respectively. Decreasing accuracy and the effectiveness of the HYDRUS-PSO model along the profile in predicting soil water content, soil ammonium, and nitrate concentrations were indicating the effects of heterogeneous condition on soil water in solute transport processes. Of course, irrigation and fertilizer methods are the other factors that influence the HYDRUS-PSO model performance. In addition, the field studies and uncontrolled conditions on the farm level are other factors to make a heterogeneous environment that causes non-uniform behavior of the model. Decreasing model performance in predicting soil water content could be related to sand content variation and the difference between the saturated hydraulic conductivity of the surface and subsurface soil. The trend changes in soil nitrate concentration in both two studied depths were indicating the amount of soil nitrate did not reach the level of toxicity and did not accumulate nitrates in the soil. Precipitation intensity, irrigation volume, and soil porosity are the most effective factors in the leaching soil nitrate issue. Based on the obtained results it could be mentioned that applied irrigating and fertilizer methods do not lead to accumulating soil nitrate. In addition, the accumulation of root systems and their extension are the other factors in the no accumulation of soil nitrate. Although, these factors had an effective role in the model performance and intensified the soil heterogenic. According to the obtained results it could be mentioned that the HYDRUS-PSO could simulate soil water and solute variations along soil profile under center pivot irrigation. Therefore, the metheuristic algorithms could use in predicting parameters as a powerful and practical tool to increase the efficiency of the numerical models in water and soil studies.