Iranian Journal of Soil and Water Research
Year:2018 | Volume:49 | Issue:4 |Papers Count:20

Impacts of observed changes in the amount and temporal pattern of precipitation on surface runoff and extreme hydrological events at local and regional scale in dry and semi-dry parts of the country is a controversial subject. In this study, the effect of observes changes in temperature and precipitation on annual and monthly discharges at the mouth of the Taleghan Dam using historical hydrometric and climatic data were investigated. The results of trend analysis indicated that while the total rainfall didn’ t show any type of trend, both temperature and runoff increased during winter, especially in months of February and April. Moreover, a positive turning point was observed in the temperature at the significant level of 99% in the year of 1984. This achievement introduced the fact of changing the temporal pattern of snowfall and replacing the season of spring with winter, in terms of snow melting period, across the basin. Further investigation on snow cover, using TERRA images during 2000-2014, revealed that the area of snow cover in February had a meaningful negative trend. Regarding all factors, including positive trend in temperature, reducing the snow cover area, spring flow reduction and winter flow increase despite of constant volume of annual precipitation and runoff, confirmed the occurrence of climatic changes in the Taleghan watershed. In conclusion, the climatic changes imposed their influences on the watershed by changing the precipitation pattern from snow to rainfall and by shifting the season of snow melting. This study suggests that due to the lack of trend in the annual input flow to the reservoir dam, anthropogenic effects, in terms of changing the pattern and amount of runoff in the Taleghan watershed, are not considerable.

In this study the performance of volumetric water delivery structure of Lopac gate-Parshall flume for various geometry condition including the size of Lopac gate opening, dimensions and position of parshall flume from the lopac gate and hydraulic conditions including flow rates and the downstream condition was investigated. Analysis of results compared to the size of opening of 100 percent of the Lopac gate showed that in general, opening of 34, 45 and 68 percent in the Lopac gate dose not lead to any significant effect on the upstream depth of gate (h1), the first well of Parshall flume (ha) and the amount of energy loss (Δ E/E1) but, the size of opening of 11 and 23 percent, lead to increase h1 and Δ E/E1 up to 28. 9 and 29. 7 percent, respectively and also decrease ha up to 10. 5 percent in the free flow condition. Comparison of the results of the Parshall flume installation positions from the Lopac gate showed that in the half and equal width of flume position installation from the gate, h1 parameter increased in 6 inch parshall flume up to 2. 8 and 3. 8 percent and in 9 inch parshall flume up to 4. 7 and 4. 3 percent to the zero position respectively. Furthermore, in 23, 34, 45 and 68 percent of size of opening of gate and all of opening of the gate in 1 foot parshall flume, there was no significant difference between the h1 parameter. Comparison of results showed that there was no significant difference between ha parameters in all installation positions of parshall flumes.

One of the methods of indirectly measuring amount of soil moisture is using Theta prob device. Since it is based on the constant dielectric of soil, factors affecting the physical and chemical properties of soil have a great impact on the accuracy of the device measurement. The aim of this study is the effect of irrigation water turbidity on measurement accuracy of water content of the soil by Theta prob device. Because of this, three different soil texture (silty loam, sandy loam and loam) were on different levels of irrigation water turbidity. The levels of irrigation water turbidity include 10, 1000, 2000 and 3000 NUT. The result indicated that factors of soil texture and irrigation water turbidity in significant level (P<0. 01) have impact on measurement of humidity accuracy by ML2 Model of Theta prob device. Increasing the level of irrigation water turbidity in each of three soil texture leads to reducing the accuracy of device measurement and most errors were observed in loam which has highest percentage of clay. Also, the result showed that specific calibration of the device functions (special linear and special nonlinear) is more accurate compared to other calibration functions which indicate necessity of special calibration for all soils are tested.

The uncertainty of hydraulic conductivity plays an important role in probabilistic analysis of consolidation of soils. In current research, a computer program was developed in MATLAB and solving the governing partial differential equation using numerical finite difference method, it was applied as the basis solution to Monte-Carlo simulation. Meanwhile, the effect of number of random samples was investigated applying 100 and 1000 samples from log-normal distribution of hydraulic conductivity (related to a land located in Saravan-Guilan) into the probabilistic consolidation model. The results showed that the probabilistic distribution curve of pore-water pressure becomes flatter with time and the uncertainty increases. Increasing the number of hydraulic conductivity samples from 100 to 1000 caused negligible effect on the probabilistic distribution of pore-water pressure. Moreover, the greatest goodness of fit of normal distribution to pore-water pressure obtained close to the soil surface and 23 percent greater than the center of soil layer.

Topography is an important factor in watershed response to input rainfall. The important role of flow tracing algorithms for deriving geomorphologic parameters of watersheds to feed distributed/semi distributed rainfall runoff models is undeniable. In present research, the effects of some widely used algorithms like D8, MFD, and Lea on the performance of a semi distributed model, TOPMODEL, in different cell sizes were investigated. The model was applied in two study watersheds, Kasilian and Karde, with two different areas and climates. It was illustrated that while for all algorithms the Topo Index values increased with the increase of the DEM cell size, in a fixed cell size MFD and D8 algorithms gave the highest and lowest values of the Topo Index, respectively. The most important result drawn from this observation is the fact that the drainage area of each cell varies by changing the flow tracing algorithm. The model calibration, focusing on its important parameter “ m” which controls the amount of runoff generated by the model, compensated the effects of DEM cell size’ s increase and improved the model performance in terms of Nash-Sutcliffe index. It was concluded that using automatic calibration for enhancing the model performance could be misleading through giving unrealistic contribution of simulated surface and subsurface flow components. For example, in Kasilian watershed using D8 as the flow tracing algorithm the surface flow and subsurface flow showed the minimum and maximum contribution to the generated flow with respect to the other two algorithms, respectively. Moreover, MFD algorithm because of giving low values of “ m” in the Kasilian watershed as a humid region is not a suitable algorithm in this type of climate and is in conflict with the basics of TOPMODEL.

Increase of CO2 concentration and nutritional improvement resulting from the consumption of nitrogen fertilizer commonly increases the photosynthesis and growth of crops. This study aimed to investigate the effect of CO2 concentration and nitrogen supply on growth and physiological characteristics of wheat of Chamran variety. A factorial experiment (combined) based on completely randomized design with soil texture in two levels (sandy clay loam and sandy loam), nitrogen in three levels (0, 100 and 200 mg kg-1) in 4 replications were conducted which treatments were applied under two carbon dioxide levels (ambient 400 and elevated 850 ppm). The results revealed all the growth characteristics (except root dry weight) in the sandy clay loam soil were higher than sandy loam. Increase of the amount of soil nitrogen significantly increased growth characteristics and also increased physiological characteristics. With the increase of CO2 concentration growth parameters such as height, shoot fresh and dry weight, root dry weight and leaf area and also the RWC as well as plant physiological parameters were significantly increased. With increasing concentrations of CO2 associated with the consumption of nitrogen fertilizers vegetative indices significantly increased. In other words, increasing amount of soil nitrogen would intensify the effect of increasing concentrations of CO2. Therefore, if there is no limitation in the supply of essential nutrients, especially nitrogen, wheat growth will increase under elevated CO2 concentration.

Studies of climate change impacts on water resources need to conversion of projection of climate variable pattern from coarser scales to a suitable scale. Downscaling processes improves projection of General Circulation Models (GCMs) significantly. In this study is assessed performance of Artificial Neural Network and Support Vector Regression. Observation rainfall was collected for 1961-1990 from Birjand synoptic station. Also value of 26 predictors from CanESM2 output in Assessment Report Five (AR5) was extracted. Predictor selection was performed by Stepwise regression. Model skill was evaluated using indices R2, RMSE and NSE. Also for better analysis using of various tests such as uncertainty assessment, reproduction of descriptive statistics, dry and wet spells and monthly rainfall. Results of assessment indices showed that estimation performances of both methods in daily rainfall are relatively suitable. Value of R2, RMSE and NSE are achieved 0. 48, 1. 5 mm and 0. 47 for SVR with Polynomial kernel function in best case respectively. Results of skill model in estimation of descriptive statistics indicated that SVR with Polynomial kernel function outperforming others. Comparison of observed and downscaled monthly rainfall illustrates that SVR performs better than ANN in winter season. Also both methods have overestimation in summer months. Results of identification of dry days sowed that performance of both models is well and same. In this case ANN identified 96% dry days correctly. Results of identification of wet days showed that SVR outperforms ANN. Assessment of skill method for estimation of dry spells length indicated that both methods have more efficiently in long spells than short

Wind erosion is one of the main causes of soil and environmental degradation, the transfer of suspended particles and its sediment in irrigation and drainage networks. Due to the monsoon winds of the region, the erosion of the agricultural lands will attack the agricultural lands of the East and West Azarbaijan provinces and will have devastating effects on environmental resources and economic facilities. The high cost of using mulch and its destructive effects on the environment has led to the use of new and more environmentally-friendly materials. In this research, the effect of SBR resin polymeric material and Bacillus pasteurii microorganism on the control of wind erosion and dust storms in Jabal Kandi region have been evaluated. To simulate soil erosion, a wind tunnel with a velosity range of 0 to 15 m/s at a height of 15 cm from the bottom of the tunnel has been used. According to the results, in samples, with increasing wind speed, the amount of soil erosion increases exponentially, so that in the control sample, up to 7 m/s, the amount of soil erosion is negligible, but the velocity rate of soil erosion from 5. 51 to 240 Kg/m2/hr has increased from about 7 m/s to about 15 m/s. Also, the trend of increasing the amount of soil erosion in a sample stabilized by microorganisms is very slow and at a speed of 15 m/s, it is equal to 1. 1 kg/m2/hr and in the polymer-stabilized sample is almost zero. To test the surface resistance of stabilizaed soil samples, an penetration resistance test was used which according to the results, the mean value of the penetration resistance in the samples treated with microorganism and polymer was 58 and 76 kPa, respectively, while the penetration resistance of the control sample is 15 kPa.

One the most important methods of presenting the river geometry is the using of Digital elevation models (DEMs). Among the several factors that affect the quality of a terrain model, DEM resolution and the scale of topographic maps are the most important ones. This research addressed the sensitivity of terrain model and 1D hydraulic parameters of HEC-RAS model to different map scales in two different rivers. Besides, investigating the role of DEM resolution on the quality of cross-sections and hydraulic outputs are another aspects of this study. Results show that using 1: 2000 and 1: 5000 maps instead of 1: 1000 and 1: 2000 maps in SojasRood and Sarbaz rivers, respectively lead to relative error lower than 8 % in simulating inundated extents, while the reduction of land surveying cost in both rivers is more than 77%. Also, evaluating the effect of DEM resolution on flood’ s hydraulic properties indicates that when DEM resolution getting coarser the water surface elevation (WSE) and inundated extents will be increased in both rivers. However, it should be noted that the effect of DEM resolution on inundated extents is more considerable than WSE. In other words, if the only objective of hydraulic simulation is limited to estimation of WSE, DEM resolution plays a minor role and therefore low resolution DEMs can be used.

This research was conducted with the aim of field studies to measure direct and farm water consumption of wheat under farm management in a cropping season (2016-2017) in 21 farms in Behbahan. The measured values of the net water requirement were calculated using the Penman-Monteith method (updated national water document) and also compared with the values of the national water document. The application efficiency in all fields varied from 22. 7 to 99. 7 percent. The average water productivity of wheat water in fields with sprinkler and surface irrigation systems in Behbahan was 0. 92 kg/m3. The highest water consumption in the fields under the springs was calculated to be 4626 m3/ha. The results of the comparison of the mean water requirement in the t-test showed that mean of the national document and the updated document had a significant difference of 483. 4 and 455. 0 mm, respectively. The Pearson correlation coefficients showed that the changes in the volume of water consumed had significant changes at 1% level and not related to the trend of changes in application efficiency and water use productivity. Also, increase of consumed water in studied fields resulted in decreasing water productivity.

The dynamical simulation model of WOFOST is widely used for yield estimation at farm and regional scales as well as different climate conditions. In modelling processes, there are lots of parameters which have to be estimated (calibrated) and also in the other hand there are limitations for providing enough observational data. Therefor it is required to choose sensitive parameters for model calibration. In this study, a global sensitivity analysis has presented for maize and wheat simulation in WOFOST model. Global sensitivity analysis methods are useful tools to rank the model parameters based on their influence on model outputs and considering the entire range of parameters. In other words, these methods consider the influence of a unique parameter as well as the influence of its combinations with the other parameters. In this paper, Regional Sensitivity Analysis (RSA) method is applied as a global method and its results are discussed. The variations of sensitivity index for the two crops are obtained from minimum 0. 006 (insensitive) to 0. 37 (high sensitive). Furthermore, Results for maize crop showed that the parameters which are related to temperature process (TSUMAM, TSUMEA) and absorbed radiation (SLA, AMAX, EFF) are among the most influential parameters in simulation of maize crop yield. In case of wheat crop, only the parameters which are related to absorbed radiation process (SLA, RGRLAI, AMAX, and EFF) are identified as most influential parameters.

Climate change could largely affect the surface water and groundwater sources. This impact should be simulated using appropriate models. In the present study, using LARS-WG and SDSM statistical models, the output of HADCM3 general circulation model under four emission scenarios was downscaled in the Hablehroud Basin in the period of 2018-2047. The SWAT model was calibrated in the basin and utilized to simulate the discharge, groundwater recharge, and soil water content in the mentioned period. Three different methods including Hargreaves, Penman-Monteith and Priestley-Taylor in the SWAT model were used to estimate reference evapotranspiration. Different combinations of the factors effecting the uncertainty, including downscaling model, emission scenario, and evapotranspiration estimation method were used. The results showed that the method used in downscaling the output of the general circulation model is the most effective factor affecting the uncertainty of the output of the SWAT model. It was also observed that the different combinations produce more outliers in simulating groundwater recharge, in comparison with simulating the discharge and soil water content. The median of the annual discharges simulated using all combinations was calculated to be 13. 32 cms. The results showed that the combinations of downscaling model, emission scenario, and evapotranspiration estimation method that simulate values less than 13. 32 cms have less uncertainty than other combinations. In the case of groundwater recharge (with a median of 2. 07 mm/ year) and soil water content (with a median of 112. 4), same results were observed.

The emitter is a device used to dissipate pressure and to discharge water at a constant rate when pressurized water flows through its narrow and long path channels, hence emitter is the key component of the drip irrigation system. On the other hand, production of a suitable emitter is expensive and time– consuming. The use of computational fluid dynamics (CFD) can be a useful tool for reducing the time and cost of manufacturing of drip emitters. For this purpose, in present study three different types of drip emitters (with different channel geometry) were chosen and their structural parameters are determined using SEM. Rate of discharge of emitters were simulated by 4 turbulence models (standard k-ε ، RNG K-ε ، K-ε Realizable، standard k-ω ) and Laminar model compared with experimental discharge. Results showed that on the whole there was generally good agreement between the experimental results and those obtained by different turbulent and laminar models. But among the studied models, results of standard k-ω and standard k-ε had the best and the worst agreement with experimental results, respectively. So that, the mean NRMSE of three emitters for standard k-ε and standard k-ω models was determined 7. 57 and 3. 56 percent, respectively. As well as with regards to low Reynolds number, the laminar model also presented good results.

Optimization of cropping pattern is one of the most important methods to increase water productivity and protect the limited water resources throughout the country. The objective of this study was optimization of cropping pattern in Dehloran plain based on spatial variations of water quality, water availability, chemical and physical characteristics of soil, and groundwater level. To this end, the Dehloran plain was divided into four zones: area covered by the Meymeh networks, Doyraj, Tropical systems and lands covered by wells. Then, AquaCrop-GIS software was calibrated and validated by filed data. Finally, the production functions were extracted and the cropping pattern was optimized using the linear programming method and the objective function of maximum net benefit. The results showed that AquaCrop-GIS are a robust tool for analyzing spatial variation of parameters affecting yield and cropping pattern in a plain. Moreover, crop pattern optimization related to water quality and quantity features beside soil physical and chemical properties could be influential on the net benefit and water productivity to be increased by 30 to 120 percent in different regions of Dehloran plain.

The optimum capacity of a reservoir is affected by two important assumptions considered in the design phase. The first one is the selected operation policy which means releasing flow at the operation time. The common reservoir operation policies in researches, mainly include the Standard Operation Policy, S-Type, SQ-Type and the techniques based on them such as GSQ-Type, GSQD-Type. The second effective parameters are assumed reliability levels and the allowed deficit threshold for water supply. In this study, the simultaneous effect of the selected operation policy, the reliability range, and deficit threshold on the optimum reservoir capacity of Marbareh in Lorestan province was investigated. For this purpose, determination of the optimum reservoir capacity in 4 operation modes which was predetermined as operation without any preset policy (Free Policy), SOP and S-Type and SQ-Type linear operation strategies considering concurrent reliability levels and deficit thresholds was performed. The results show that the optimum reservoir capacity was severely influenced by reliability levels, deficit thresholds, and selected operation policy. So that, in this study the reliability change from 50% to 100% changes the minimum reservoir capacity for different modes of operation policies and the accepted deficit thresholds from 5. 2 MCM to 248. 3 MCM. The effect of the uncertainty of the stochastic parameter of the inflow into the reservoir is considered by implicit method (using statistical series).

spur dike is a hydraulic structure that is created in open channels and rivers to protect the walls against erosion or deviations and water guidance in the desired directions. The most important problem of spur dikes is scour at around it that makes breaking and overturning the spur dikes. Considering that the flow pattern and topography of the bed is significantly affected by the presence spur dike, it is important to consider these issues. in this purpose, the effect of variations in the length of the gabion spur dike with porosity of 30 & 50% was investigated in this study. For measuring 3D velocities and bed topography, Vectrino+ was utilized. 3D velocities were measured in movable bed state. Finding show that increasing the length of the spur dike, the maximum depth of scour and scour hole dimensions increases. According to the results of flow pattern experiments in this field, increasing the section constriction and consequently, increasing the flow rate in cape of spur dike with developments secoundary Flows increases the maximum depth of scour and scour hole dimensions. By increasing the length of the gabion spur dike, the range of the effect of this structure on its upstream is increased, so that the velocity changes through the canal and approaches the opposite wall. The highest rate of velocity in all layers, after a gabion spur dike in the range near the side, extending towards the middle channel.

Flavonoids play a crucial role as signal molecules in promoting the formation of nodules by symbiotic bacteria commonly known as rhizobia. Luteolin is one of the most important flavonoids, which release from seeds during the first 4 hours of imbibition. It also seems that high NaCl concentrations induce the nod genes the absence of flavonoid inducers. We studied the effect of luteolin, Seed exudate and salinity on the induction of nod genes in R. Meliloti carrying a plasmid with a translational fusion between R. Meliloti nodA and lacZ of Escherichia coli, and the expression activity was measured by β-galactosidase activity. The results showed that pretreatment of bacteria with luteolin and seed exudate increased the expression of the nodA gene, that the effect of seed exudate on gene expression was more than the effect of luteolin. The results also showed that high salinityو 300 and 400 mM led to the expression nod gene in the absence of flavonoids and when there is high NaCl and inducers simultaneously, the expression of nod gene was greater. It seems that, rhizobium use a possible mechanism to improve nodulation under stress conditions. Due to increasing salinity and synthetic fertilizers problem, it seems searching about salinity and symbiosis of rhizobium and legums is importan and necessary.

Land use change in the northern part of Iran has changed the quality of soil. The aim of this study was to investigate the impacts of different kinds of land use/cover, i. e. virgin natural forest, degraded natural forest, alder plantation, sequoia plantation, improved fallow and home garden areas on soil biological characters in plain area of northern Iran. For this, 30 soil samples were taken from a depth of 0-10cm in the studied land use/covers. Density and biomass of earthworm ecological groups, soil nematodes density and the rate of carbon dioxide emission were evaluated from top soil during 4 seasons. Also, some physicochemical properties were measured at the laboratory. The maximum of earthworms density, (3 n m-2), earthworms biomass (38. 76 mg m-2), nematodes density (457 in 100 g soil), and the emission of carbon dioxide (0. 47 mg CO2-C gsoil− 1 day− 1) belonged to Alder land cover. In all the studied land use, every three groups of earthworms and nematodes had jointly the highest activity in the spring and autumn, while the highest amount of carbon dioxide emissions was recorded in the summer. PCA showed the highest positive effect the soil pH, nitrogen and nutrients with biological properties. As a result, it can be concluded that plantation with Alder species is a good way to improve biological indicators and maintain soil quality in degraded areas of forests in the northern Iran with similar condition.

One of the most important factors of the water quality management is the rate of dissolved oxygen. Reaeration coefficient describes the rate of absorption of oxygen from atmosphere into water. The rate of dissolved oxygen in water quality modelling shows great sensitivity even to the smallest changes in reaeration rate coefficient. The main target of this paper is to evaluate the best equations of the reaeration rate coefficient, among 29 most used equations based on the dissolved oxygen modelling for Karun River, IRAN, in different seasons. In order to achieve this aim 91 km length of river, from Molasani to Kut-Amir stations was modeled. Modelling was performed based on monthly quality and quantity data of this river, from 2010 to 2011 and also 2011-2012, involving Qual2Kw5. 1 software. According to the results Thyseen (TH) equation in the autumn, Lau (LA) in winter and spring and finally Jha (JH) equation in summer have the best estimations for the reaeration rate coefficient, while the accuracy of the modeled DO values were evaluated using RMSE between simulated and observed data, which were equal to 0. 35, 0. 48, 0. 29 and 0. 29, respectively. Also the MBE values were equal to 1. 78, 0. 43,-2. 47 and-0. 67, respectively, which show very good agreement. Finally, the relevant modeled reaeration rate coefficients for the above mentioned seasons were equal to 0. 62, 0. 23, 0. 33 and 1. 59 (1/day), respectively.

In order to study of effect of saline water and soil fertility stresses on the evapotranspiration of maize, a factorial experiment was conducted in a randomized complete blocks design, in the research farm of Imam Khomeini International University, in 2017. Water salinity treatments consisted of four levels; 0. 5(S_0 ), 2. 1(S_1 ), 3. 5(S_2 ) and 5. 7(S_3 ) d_s/m and Soil fertilization treatments consisted of four levels of need to nitrogen fertilizer; 100(F_0 ), 75(F_1 ), 50(F_2 ) and 25 percent (F_3 ), was conducted In three repetitions and in plots with an area of 9 square meters. By measuring the soil moisture at the root zone, at intervals between two irrigations, was investigated the difference of water absorption by stressed plots relative to non-stress plot. The results showed that by changing the salinity of irrigation water from 0. 5 to 5. 7 (d_s/m), in fertolity levels of F_0, F_1, F_2 and F_3, the stress coefficient of evapotranspiration (K_S ) has been; 0. 77, 0. 69, 0. 64 and 0. 6, respectively. Also, by changing the fertility level from F_0 to F_3, in salinity levels of S_0, S_1, S_2 and S_3, the K_S has been; 0. 96, 0. 88, 0. 83 and 0. 63, respectively. From treatment of S_0 F_0 to S_3 F_3, were reduced the evapotranspiration, K_S coeffition and crop yield to; 37, 37 and 38 percent, respectively. Are fitted different forms of production functions, to estimation of evapotranspiration from salinity and fertility stresses. The quadratic function was chosen as the optimal function due to having the statistics of RMSE and ME at least and R^2 and EF close to number one. The salinity and fertility stresses, has a reducer effect on the amount of evapotranspiration of plant. Therefore, by correct determination of water requirement of under stress plant, you can avoid than consumption of a lot water.