WATER AND SOIL SCIENCE (AGRICULTURAL SCIENCE)
Year:2021 | Volume:31 | Issue:1|Papers Count:12

Soil water content (SWC) is an important physical factor that plays an essential role in many processes such as infiltration and soil erosion. This study was conducted to investigate the effect of SWC on runoff and soil detachment from rills in coarse-grained soils in the semi-arid region. For this purpose, furrows with 6 m in length were installed in five rainfed farms with different slope steepness (6. 1, 10. 6, 14. 8, 20. 7 and 27. 1%) treated with four moisture levels including air-dried (AD), between air-dried and field capacity (AD-FC), field capacity (FC) and saturation point (SP) in a completely randomized design witht three replications. Flow rate with a discharge of 2 L min-1 was used to investigate soil detachment from the farms. The soils were coarse texture (having 5675% sand) and rocky (having 22-57%) with unstable structure and high infiltration rate. Based on the results, soil detachment decreased with increasing SWC in 6. 1, 14. 8 and 20. 7 % slopes. The highest soil detachment rate (g m-2-1 s ) in these lands was observed in AD-FC (0. 01), AD (0. 306) and AD (0. 0045), respectively. By increasing SWC, the continuity and stability of soil mass of furrow increased, and runoff occurred mostly as subsurface flow in the rills. Surface runoff as well as the soil particle detachment decreased in the rills. Therefore, in the semi-arid slopes with coarsegrained soil, soil detachment rate decreases with increasing SWC.

The aim of this study was to investigate the efficiency of the neural network model in quantitative and qualitative modeling of groundwater resources. For this purpose, the groundwater of the Najafabad aquifer located in Gavkhoni basin at the central plateau of Iran, was modeled using MODFLOW and MT3DMS modules of GMS v. 10 software. After calibrating and validating the model for a 11 years time period, the ranges of hydraulic conductivity, specific yield and longitudinal dispersivity coefficient were found to be 0. 5-16 (m day-1), 0. 023-0. 113 and 7. 5-18. 2 (m), respectively. Then the study area divided into two sub-regions and the ANN model was designed for each of the sub-regions. Afterwards, the optimal parameters of the ANN models were determined using the 20-year dataset of water year and the genetic algorithm optimization model. Finally, calculated values relevant to the average level of groundwater and the mean concentration of TDS, which were acquired by the ANN model and the numerical model, were compared with the observed values from 2014 to 2016. Results showed that the neural network model is capable in simulating the quantitative and qualitative treatment of the groundwater system and can be used as a suitable alternative for the numerical model linking the management models.

The permeability is one of the most important physical properties of a soil that has been used in geotechnical engineering. Soil permeability generally depends on several factors, such as soli properties containing the porosity, surface roughness of solid particles, Saturation and fluid (water) properties which passes through the soil. In order to do the research a testing device is designed for measuring horizontal and vertical permeability of the coarse particles. In this study, four uniform soil samples and three non-uniform samples with different compactions are selected and tested under various water heads. The results show the permeability in the horizontal direction is often greater than the permeability in the vertical direction and this difference in non-uniform sample is greater than that in uniform samples. The permeability anisotropy ratio for uniform samples is between 0. 85-1. 35 and for non-uniform samples is between 1. 32-3. 5. Also, with increasing the uniformity coefficient the rate of anisotropy permeable decreases.

Changing the cropping pattern due to the climate change and drought persistence is one of the key approaches for agricultural policy makers for adaptation of water scarcity. Also, implementation of changing the cropping pattern in Sarab County is felt as one of the major points of agricultural production in East Azerbaijan province. Since the uncertainty is one of the unavoidable aspects in agricultural planning and decision making, this study introduces and applies the robust goal programming (RGP) model as a tool for optimization of cropping pattern under uncertainty in Sarab County. The required data and information for this study were collected through Sarab County Agriculture Organization and completing the questionnaire in the period of 2017-2018. In addition to the RGP approach, the LP and GP models were solved to determine the optimal cropping pattern. The results showed RGP model in terms of achieving the goals of maximize profit and minimize water consumption was superior to other models, which indicated that the current status of the water operation in the studied area was not optimal. Implementation of optimal cropping pattern based on RGP model would increase profited and employment by 1. 7 and 1. 32 percent, respectively. It also could reduce water consumption, fertilizer and chemical pesticides consumptions by 7. 7, 12. 3 and 12 percent, respectively relative to the current cropping pattern. Among the studied crops, wheat had the highest increase regarding cultivated area. Therefore, wheat is an important crop in the region and it should be cultivated as a strategic crop in greater area.

In this research, an evolutionary based Neuro-fuzzy technique was utilized to estimate the discharge coefficient of labyrinth weirs. In order to optimize the parameters of the adaptive Neuro-fuzzy inference system (ANFIS), the Firefly Algorithm (FFA) was implemented. In modeling the ANFIS-FFA and ANFIS methods, the Monte Carlo simulation was used to evaluate uncertainty of the model. Furthermore, several models with significant flexibility and generalizability were provided using the k-fold cross validation method. First, the input dimensionless parameters including the Froude number (Fr), ratio of the head above the weir to the weir height (HT/P), cycle sidewall angle (α ), ratio of length of the weir crest to the channel width (Lc/W), ratio of length of the apex geometry to the width of a single cycle (A/w) and the ratio of width of a single cycle to weir height (w/P) were defined. After that, seven different models were introduced for ANFIS and ANFIS-FFA. Then, using a sensitivity analysis, the superior models (ANFIS-FFA 5 and ANFIS 5) and the most effective input parameter (Froude number) were identified. In addition, the error distribution results showed that about 70% of the superior model (ANFIS-FFA 5) results had an error less than 5%. In other words, the superior model had a high statistical significance. Ultimately, the uncertainty analysis for the superior models was carried out.

The stilling basins are of the most important energy dissipater structures, and changes in their shape lead to a better hydraulic performance of them. In this study, the impacts of steps at the end of USBR II stilling basin of Nazloo-Chay dam and walls convergence on the pressure, water surface profile, efficiency of hydraulic jump and energy dissipation were investigated. For this purpose, the flow was simulated using the VOF method and RNG turbulent model in the converging stilling basin (with convergence angle of 5 ◦ , 7. 5 ◦ , ◦ 10 and 12. 5 ◦ ) and discharge rate of 830 m 3 -1 s. The numerical model was verified by pressure's experimental data. The results showed that existence end steps and convergence walls led to an increase in tail water depth and prevented hydraulic jump from exhausting out of stilling basin. Also, the convergence walls caused the jump to be submerged contrary to the free jump occurring in stilling basins with parallel walls having free jumps. Convergence Walls had a positive impact on the efficiency of the hydraulic jump. In this study, the converging stilling basin with 5 ◦ convergence angel gave a great performance, and the efficiency increased by 136% in comparison to stilling basin with parallel walls. The comparison of the results of energy dissipation for different sections of stilling basin at different flow depths demonstrated that the maximum energy dissipation occurred in the depths between 20-30% of flow depth. These results may be considered for improving the stilling basins design.

Spatial variability of the soil properties is related to the environmental factors such as climate, topography, parent material and vegetation. Topography causes significant differences in soil properties through the three factors of elevation, natural drainage and slope. This research was carried out to investigate the effect of elevation on some physical and chemical characteristics, type and content of the clay minerals, and finally on the evolution of soils of an elevation profile in Talesh Mountain in Ardabil province. Following excavation and description of five profiles on non-eroded surfaces, physical, chemical and clay mineralogy experiments were performed on the samples. The results showed that weathering intensity and type of pedological processes were different and had a significant effect on some soil characteristics such as clay content, different forms of iron, minerals and soil classification at the different surfaces of elevation. With decreasing the altitude, the amount of illite minerals was reduced but the amount of smectite minerals has increased, which is a reason for the improved weathering and evolution of the soils. The results show that toeslope lands have evolved soils of Vertisols and Mollisols, but highlands have Inceptisols with low degree of evolution. Addition, in the studied elevation profile, as the altitude decreases, the climate becomes warmer and consequently the intensity of pedogenic processes increases. The increase in the amount of crystalline iron (Fed-Feo), as an indicator of soil evolution, from 2303. 9 mg kg-1 at the topslope to 7558 mg kg-1 at the toeslope of the mountain illustrates this evolutionary trend.

Zinc (Zn) is one of the micronutrients for plants and its deficiency is common in calcareous soils. Organic matter plays a key role in availability and transformation of soil Zn. In order to study the effect of leonardite on adsorption behavior and chemical forms of Zn in a sandy loam soil, an experiment was conducted in a completely randomized design (CRD) with three levels of leonardite (0, 2 and 5%) with three replications. The soil was mixed with 0, 2 and 5% of leonardite and incubated at field capacity (FC) at 25± 1 ° C for two weeks. After two weeks, adsorption experiments carried out with different initial concentration of Zn (0, 30, 90, 120, 150, 200, 250 and 300 mg L-1 Zn) with 0. 01 M CaCl2 as a background solution, and Zn-extractable by DTPA method and Zn distribution by modified Tessier sequential extraction method were determined. Among the adsorption equations, the Froundlich equation (with higher R2 and lower SE) was better fitted to experimental data compared to the Langmuier, Temkin and Dubinin-Radushkevich equations, the sorption capacity factors (qmax, B, KF, qD) and sorption energy factors (KT, KL, 1/n) decreased with application of the leonardite. The sorption energy parameter (E) of Dubinin-Radushkevich isotherm indicated that the Zn adsorption process was physical. The application of the leonardite increased the exchangeable, carbonate and organic matter forms but decreased the oxide and residual forms. The MF Values increased with increasing the leonardite levels, demonstrating an increase in the mobility of the Zn in the studied soil. It was concluded that addition of the leonardite in soil lead to transformation of zinc from insoluble forms into more soluble and increased zinc bioavailability.

Side weirs are among important hydraulic structures that used in various projects such as water conveyance, flood control, and diversion of excess water in sewer networks. One of the most effective and economical ways to increase the efficiency of these weirs is application of labyrinth side weir. Using labyrinth side weirs, the flow discharge is increased by changing the plan geometry and increasing the weir length. Due to complicated calculations related to the determination of the discharge equation for Labyrinth side weirs, extracting simple discharge relation for different conditions is necessary. Therefore, in this study, the discharge relations for rectangular side weirs having two opening values of 0. 3, 0. 5 m and for labyrinth side weirs having 90, 60 and 45 apex angle with opening values of 0. 3, 0. 5 and 0. 6 m were extracted. Comparison of the simulation results with these relations indicated that the accuracy of the relations was within ± 15% which was acceptable for practical purposes. Also due to the results of labyrinth side weir, with decreasing the weir effective length, the flow discharge reduced when the apex angle of labyrinth side weir was increased for a constant water head. Decreasing the effective width also caused the flow discharge to be reduced when opening was decreased for a constant water head.

Agricultural sector is the greatest user of water in Iran, and increase of the consumption efficiency is necessary by considering the limited water resources in the recent years. Hasanlu irrigation and drainage networks as a part of a larger project of Naghdi plan is one of the country's largest projects in the field of development of pressurized irrigation systems. Hasanlu network supplies water to the systems of sprinklers, surface gravity irrigation, and hydroflums based on the available pressure head at the relevant sites. In this research, geographic information systems were used as a framework for storing, management, processing, analyzing and visualization of spatial information of Hasanlo project phase 1 to evaluate water management of this plan. For this purpose, the coefficient of uniformity and distribution uniformity in sprinkler irrigation calculation toolbox developed and added to GIS as an extension, to simulate and evaluate the single or multi riser uniformity tests. Also, the risers discharge and application pressure were recorded at the site during the operation of the project. Results indicated that the pressure of risers varied from 0. 5 to 3. 9 bar and average Christiansen’ s coefficient of uniformity (CU) was under 50% that indicated poor water management in the farm level. Also, the satisfaction of stakeholders was in medium level.