نشریه دانش آب و خاک
سال بیست و هفتم شماره 1 (بهار 1396)

Forest fire causes major changes in soil properties but little is known about the persistence time of the changes over the years following a fire. This study was conducted to investigate the remain effects of fire (summer 2011) on some properties of surface (0-5 cm) and subsurface (5-10 cm) soils after three years (summer 2014) in Tapeh Darvish forest which is located around Zarivar Lake in Marivan city. A control safe place was selected on beside of the burned area with similar conditions, but not affected by fire. Three composite soil random samples were taken from the each mentioned depth of the burned and control sites. The differences between the measured properties at the burned and control sites were assessed by independent t-test (P=5%). The results showed that there were not significant differences between the soil samples properties of texture, color, carbonate calcium equivalent (CCE), electrical conductivity (EC), pH, cation exchange-capacity (CEC), nitrate and total carbon and nitrogen in the burned and unburned sites. However, burning significantly incresed the available amounts of calcium and magnesium in both surveyed soil depths and phosphorous and potassium in surface soil. Furthermore, the amount of ammonia in burned soils was significantly lower than that in unburned soils in both surveyed soil depths. Altogether, the results of the study showed that the effect of fire on the available amount of nutrients, especially in the surface layer of soil still persistantly remained 3 years after the fire.

This study was conducted to determine suitable soil tillage method. It was carried out for two years in summer planting soybean in the form of stripe-plot with randomized complete block design with four replications on the farm of Agricultural Research Center Moghan. In this experiment, the first factor was three tillage moaldboard plow and disk harrow; Chisel plow and disk harrow and only disk harrow and the second factor included three soybean varieties ( Zane , Williams and L17). Moisture content, bulk density, penetration resistance and crop residue levels before and after implantation and agronomic traits such as grain yield, emergency precentage, plant height, the height of first pod, the number of pods per plant, pod length and the number of grain per pod were measured. Two-year results of the experiment showed that different methods of soil tillage did not cause any significant difference in the grain yield. But the agronomic traits such as plant height, pod length and number of grain per pod showed significant differences at 1% probability. The two-year results of this study also showed soil tillage treatment differences in terms of cone index at the depths of 0-10 and 10-20 cm, but at the depth of 20-30 and 30-40 no significant difference was detected. The lowest and highest cone index in 0-10cm depth were 0.54 and 0.60 MPa with the moaldboard plow and disk harrow and only disk harrow , respectively. Also The two tillage treatments at 10-20 depth with 0.72 and 0.59 Mpa had the highest and lowest cone index, respectively. The difference between treatments was significant in terms of MWD, as Moaldboard plow and disk harrow, Chisel plow and disk harrow and only disk harrow with respectively 16.3, 13.0 and 10.1 mm were divided into three different groups. The index of return of plant residues with averge of 82.41 and 69.83 in the first and second years was statistically significant at the 1% level. On the other hand, the three tillage methods did not lead to significant effect in bulk density and the soil moisture content percentage.

Submerged vanes are thin rectangular structures which have angle with respect to the flow direction, creating high and low pressure zones on both sides of the vanes. These structures generate a secondary vortex, change the near-bed flow pattern, and consequently alter the pattern of the sediment transport and erosion within the channel cross section. The function of submerged vanes to reduce scour around the bridge piers and movement of the sediments in the region of vanes, due to down flow in front of them, are affected by arrays of the vanes. Another factor affecting the performance and efficiency of a submerged vane is its shape. In the present study, a physical model was used to investigate the effect of various shapes of vanes including flat-rectangular, convex, concave, flat-convex, flat-concave, reticular, and angled vanes on bridge pier scouring reduction. To this end, a cylindrical bridge pier with the diameter of 2.54 cm was modeled in a 10m-long and 0.3m-wide flume under clear water condition with v/vc=0.96. The length of the vanes was equal to the width of the pier and the vanes were installed on the bed. The highest level of reduction in scour depth was observed for acuminate vanes compared with the unprotected pier. Furthermore, convex vanes showed better performance compared to the flat vanes at angles of attack 20° and concave vanes.

Turbidity currents are the main factors of sediment transportation and deopsition in reservoirs. In this research, the effect of porous sheets and permeable obstacles in controlling the turbidity currents has been studied experimentally. Plexiglas sheets with the thickness of 2 mm were used to build porous sheets and hollow plastic cubes were used for building porous obstacles with dimensions of 2.1 × 2.1 × 2.1 (cm). The surface porosity was assumed about 25% for the both models of obstacles. The experiments were performed in a slopping flume at the length of 10 m with three different slopes. During the expriments, the concentrations of the turbidity current at upstream and downstream of the porous sheet and the porous obstacle were measured using suction probes. In case of the porous sheet, the turbidity current entered the pores longitudinally, while in case of the porous obstacle, it entered the pores in two perpendicular directions. The result showed that in the case of utilizing porous obstacles, a rotational flow was formed as the turbidity currents entered in two perpendicular directions which increased the dissipation of the turbidity current’s energy in the porous obstacle application compared to the porous sheet application. Furthermore, by increasing the relative height of the obstacle in both zero-slope and non-zero slope cases the performances of the both porous obstacles and the porous sheet were increased.

For proper management of soil, conducting a comprehensive assessment seems necessary and basic. Soil forming processes strongly vary among different land uses and topographies. In this study, a factorial experiment was performed in a completely randomized design with 2 factors (type of land use and soil depth) in 3 replications, in order to investigate the impacts of topography and different land uses on soil physical, chemical and mineralogical properties of soils of Chaypare, West Azerbaijan province, Iran. There were three dominant land uses including pasture (low density of vegetation cover), dry farming (mainly wheat without annual alternating crops) and irrigated farming (with annual alternating crops). In the present study, two soil profiles were dug for each land use and then clay mineralogy, along with the physico-chemical properties, were determined. The results indicated that changes in the both topography and land use influenced the soil cation exchange capacity (CEC) through affecting both the clay and soil organic matter contents. Although, there were no significant differences in physic-chemical properties among different land uses, the soils of irrigated farming showed relatively lower amounts of calcium carbonate equivalent (CCE) and sand content than the two other land uses and the amounts of organic matter content and CCE and pH were considerably dominant in the irrigated farming. The X-ray diffraction (XRD) measurements indicated that both the topography and type of land use had no significant effect on the qualitative properties of the clay minerals but they were effective on their semi-quantitative properties. Accordingly, the amount of smectite in the fine clay fraction in the irrigated farming was dominantly higher than that of the other land uses. Additionally, the status of the different cultivated crops seemed to affect the quantity of clay minerals in the both dry and irrigated farming land uses. Finally, the irrigated farming compared with the two other land uses (pasture and dry farming), revealed to be more affected by the slope and pedogenic processes.

Density currents are formed due to gravity face action on the two fluids with different densities. This paper investigates the effect of radius of stream route curvature on the velocity and concentration profiles in density current. Experiments were conducted in a flume with three different curvature radii of 40, 80 and 120 cm. Acoustic Doppler velocity meter was used to record the instantaneous downstream (u), cross stream (v) and vertical flow (w) velocities. Before entering the bend, the flow is longitudinal. In open-channel bends, surface flow moves towards the outer bank and the flow on the floor moves towards the inner bank. Results showed that in density current the maximum stream wise velocity occured near the stream bed. Due to density stratification, in addition to the difference in height, generated pressure difference force was not constant throughout the depth of a density current and depended on reduced gravity and Concentration profile of flow. As a result, lateral flow reversed and near-bed flow towarded the outer bank. With increasing the radius of the flume curvature, circulation cell became poor and smaller.

Nowadays, due to the population growing and agriculture lands degradation, optimum land use and management become essential. Consequently land suitability evaluation and prediction of the production potential are important processes. The goal of the present research is the comparison of AEZ and Wageningen models in estimation of the Thermal-Radiation production that it is one of parameters in calculation of the Production Potential in FAO method for irrigated wheat. Soil morphological, physical and chemical characteristics of 10 land units of Khajeh region with 1100 ha extension located in East Azarbaijan province were selected. The soils of the study region have Aridic border to xeric moisture and mesic temperature regimes, and were classified in Aridisols orders according to keys to soil taxonomy 2014. Coefficient of correlation values between land production potential and observed yield were 0.74 and 0.72 for AEZ and Wageningen models respectively. Geometric mean error ratio (GMER) index was used for studying the model accuracy. The values of this index have been calculated for the AEZ and wageningen models 1.02 and 2.28 respectively. According to the coincidence of agreement maps of the AEZ or wageningen models and observed yield the agreement in AEZ method 52.8 % is more than of the Wageningen method 12.8%. Finally, the AEZ model is more efficient than the other because it has high precision, accuracy, overall map agreement with observed yield and low calculating process.

The estimation of soil moisture plays an essential role in the hydrologic modeling, drought prediction and management, climate change analysis, and support of agricultural decision making. Therefore, by use of meteorological parameters variations in the future period, effect of climate change on soil moisture status were investigated by use of three models of AOGCM and emission scenarios namely B1, A2 and A1B. So, firstly, the values of temperature, rainfall, relative humidity, wind speed and radiation were determined by these three scenarios and AOGCM models and secondly downscaled by the LARS-WG model and change factor method. Results of the present study showed that the values of temperature, relative humidity, wind speed and rainfall would increase in average by mean of 8%, 7%, 1% and 5% respectively, in the future period (2020-2039) in comparison with the baseline (1992-2011) and also temperature and relative humidity would increase in average by 30% and 19% in the future period (2080-2099) as compared with the baseline. Also, soil moisture at the depths of 30 and 60 cm were determined by use of meteorological parameters, soil and water data in SWAP model for future and base line periods. The results showed that the soil moisture in the future period of 2020 would increase as compared with the baseline, but in the future period of 2090 would decrease. Furthermore, the 5th and 21th weeks of the wheat growing season were determined as drought stress warning weeks for the Faroub and Soleimani farms, respectively.

The aim of this study was to investigate the effect of fractal dimensions of particles (Dy) and aggregates (Df) as extra inputs on improvement of the estimation accuracy of wet mean weight diameter of aggregates (MWDwet) using regression and artificial neural network (ANN) pedotransfer functions (PTFs). Consequently, 90 soil samples were taken from agricultural, range and forest lands of Ardabil Province. Yang et al. and Rieu & Sposito fractal models were fitted to the primary particles (0-2 mm) and aggregates (0-4.75 mm) size distribution data, respectively, and the Dy and Df values were obtained. The MWDwet value was also determined by the wet sieving method. The results indicated that there was a significant positive correlation between wet MWDwet and Dy values and a negative correlation between wet MWDwet and Df values. Using Df as an input variable increased the R2 criteria from 0.71 to 0.80 in regression-PTF and from 0.78 to 0.95 in ANN-PTF at training stage. Adding Df as a predictor could not increase the validity of the developed PTFs. The PTF developed by ANN had higher accuracy than the PTF developed by regression method. The R2 values for training stage in ANN-PTF with using of Df as predictor was 0.95 and in regression-PTF was 0.80.

Waterhammer is one of the destructive hydrodynamic phenomena which is established in most pumping stations, transmission lines and hydroelectric power plants. This phenomenon rises the abnormal pressures, cavitation occurence and finally pipe explosion and disturbance of the whole system. So, its accurate investigation is known as one the first and main steps in designing, which by compelet identifying the effects of waterhammer, the hydraulic facilities remain safe from the dangers of this phenomenon. To control the destructive effects of this event, different methods are advised. One of these methods is sometimes enough and a combination of two or more is necessary in some occasions. This paper is an attempt to study the waterhammer phenomenon in a pumping station and solve the governing equations with the use of characteristics method. In order to compare the effects of different methods on controlling the pressure due to waterhammer, the mentioned pumping station considering the presence of flywheel, surge tank, air chamber and a combination of air chamber and surge tank has been investigated. The result indicates that use of air chamber is the best instrument among the mentioned methods, to control the waterhammer destructive pressures.

Increasing concentration of heavy metals causes considerable harmful effects on soil. Due to enhanced application of fertilizers, pesticides and also increasing urbanization and industrial activities, accumulation of heavy metals in medicinal plants may be occurred. In this research, effects of chromium toxicity on some morphological characteristics and essential oil chemical composition of basil (Ocimum basilicum L.) under controlled conditions were studied. Therefore, effects of six treatments of Cr (control, 0.01, 0.1, 1, 5, 10 mM) based on a completely randomized design with 4 replications in perlite culture was studied. The results of data analysis of variance showed that the effects of different concentrations of Cr on morphological characteristics of shoot and root and essential oil chemical composition were significant. The application of different Cr concentrations decreased morphological characteristics, this reduction was a significant amount compared to the control treatment. It was observed that substrate pollution with heavy metals like Cr inhibited the absorption of essential elements to the plants shoot and thus, repelled the growing process. Different concentrations of chromium increased main compounds of Basil essential oil, such as Linalool and Eugenol and this rise was the result of the stress of chrome and induction of defense responses and stimulation of the bio synthesis's path and the accumulation of essential oil.

Water flow through obstacles such as bridge piers results vortex waves. The overlap of vortices resulted from any obstacles, contributes to transverse waves, perpendicular to stream. When the vortex frequency and stream natural frequency become equal resonance occurs and the maximum amplitude resulting from transverse waves may cause destruction of the structure. These waves can also affect suspended sediment transportation. This study was carried out to determine the vortex frequency of obstacles at various arrangements through stream during wave resonance and the effect of flow variations on vortex frequency. Therefore, some experiments were conducted with a rectangular flume at constant discharge using cylindrical and prismatic obstacles with triangular cross section and with water flow directed at the edge or face. The frequency of waves for in-line and staggered arrangements was determined for the two oscillation modes. The obstacles frequency and flow natural frequency were compared at different arrangements and various obstacles with collecting flow characteristics at two modes. Non-submerged obstacles produced larger wave amplitude than submerged obstacles, with the frequency of stream being close to the vortex frequency. Finally, some equations were developed for determining the Strouhal Number of different obstacles using statistical methods and data analysis.

In this research, a multi-layer perceptron neural network (MLP-NN) model was used to simulate dissolved oxygen and total phosphorus in the Ilam Dam catchment. The NN model was developed using experimental data from three sub- catchments of Ilam Dam during the 2009-2010 period. Input variables of NN model including water PH, electricital conductivity, total suspended solids, temperature, total phosphorus, sulfate, ammonia, iron and total nitrogen were employed for the dissolved oxygen modeling. Input variables for total phosphorus modeling were temperature and phosphate, which have been measured at one station on the reservoir vicinity at different depths. The performance of the models was assessed by the coefficient of determination, relative error, and sum of squared errors (SSE) indices. The neural network results indicated that all the input variables affected modeling of the dissolved oxygen concentration, while the most effective parameter was the total suspended solids. Phosphate presented the highest impact on the total phosphorus modeling than the temperature. The cofficient of determination values for modeling dissolved oxygen and total phosphorus were 0.813 and 0.940, respectively. The results of NN models were then compared with the two-dimensional, laterally averaged CE-QUAL-W2 model. Based on the results, the multi-layer perceptron model showed more accurate responses than the numerical model in predicting water quality variables. Results also showed that the NN was able to predict the eutrophication process with acceptable accuracy and could be used as a valuable tool for qualitative management of reservoir water.

Labyrinth weirs are widely used for controlling and regulating flow rate in rivers and canals as well as for conveying flow from upstream to downstream of dams. In this study, the discharge coefficient of the different kinds of labyrinth weirs was predicted by using support vector regression (SVR) technique. Totally 527 laboratory test data were used for predicting discharge coefficient of four different types of weirs including: normal and inverted labyrinth weirs in flume and arced labyrinth weirs with and without the nappe breakers in reservoir. The root mean squared error (RMSE), coefficient of determination (E or DC), and squared correlation coefficient (R2) statistics were used to evaluate the models’ performance. The obtained results showed that the support vector regression technique had a high capability of predicting discharge coefficient of labyrinth weirs .Statistical evaluation criteria of the best model for normal labyrinth weirs were R2=0.990, DC=0.988, RMSE=0.0077 in validation stage. The results of sensitivity analysis showed that (Fr, HT/p) and (HT/p, α/θ) were the most influential parameters for the labyrinth and arced labyrinth weirs, respectively.

Many mathematical classic methods have been suggested for predicting sediment transport in order to prevent or minimize damages caused by the erosion and sedimentation. These methods are mainly based on some statistical methods and field - laboratory data which have been suggested by many researchers such as Yang, White, Bagnold, and Hansen. The results obtained from the classical methods for predicting sediment transport revealed poor performance of these methods under different hydraulic conditions and the high sensitivity of them to river conditions and bed particle size. In this paper, performance of evolutionary systems for predicting the bed load transport in a gravel bed river was evaluated. For this purpose, the genetic programming method was used and the inputs parameters required for modeling were selected and optimized according to the parameters governing the classical methods as well as the basic concepts used in the structure of these methods. The data used herein was obtained from sampling Yazdekan Bridge station of Ghotourchay River which is located in West Azarbaijan and within the city limits of Khoy. In different stages of modeling, effect of different factors on performance of evolutionary systems was investigated and the optimized structure for each of these models was determined. Next, the results were compared with the classical methods. The obtained results showed high capability of intelligent methods comparing to other classic formulas for predicting the bed load in a gravel bed river

In order to investigate the effect of soil compaction on soil nitrogen mineralization process and its uptake by wheat a factorial experiment in a completely randomized design with three replications was designed. Experiment was conducted with three levels of compaction (normal, 10% and 20% compression), two soil textures (sandy and clay) and five sampling times (1, 7, 14, 30 and 60 days after planting). Ammonium and nitrate concentrations in soil were measured at five time intervals. Results indicated that the effect of soil compaction, time interval and the interaction of soil compaction and time intervals on concentrations of ammonium and nitrate were significant (p

Drought is one of the recurring meteorological events that occurs in whole of the world and leads to water scarcity, economical hazards and devastating social consequences. Traditional methods of drought monitoring often depends on meteorological data especially on precipitation data. Due to the low spatial resolution and some missing values of ground based data, estimation of meteorological drought indices from these data is not reliable. Remote Sensing techniques with fine spatial and temporal resolutions are considered as useful tools for agricultural drought monitoring. In this study, spatial and temporal distribution of agricultural indices (DSI, VCI, TCI) were evaluated in the East Azerbaijan Province during the years of 1382 to 1393 (Iranian calendar), using the satellite images of MODIS. Also correlation between agricultural drought indices based on remote sensing data and meteorological drought index (SPI) was investigated. Results showed that the remote sensing indices had a good accuracy in the monitoring of agricultural drought, for instance the correlation coefficient between DSI and SPI indices was 0.64. Evaluation of SPI and agricultural drought indices indicated that moderate drought occurred in the most stations in 1387. However, the northern areas (Aras riverside) had a better vegetation condition in comparison to other regions even at dry year of 1387 and SPI index values were equal to -0.38 and -0.53 for Jolfa and Kaleybar stations respectively, that confirmed this matter. Statistical analysis showed that the highest correlation between agricultural and meteorological indices was in Jolfa station, where the highest mean amount of SPI index was 0.6.

Soil chemical properties are important because they may have significant effect on the soil physical properties, activity of microorganisms and plant growth. For improving soil chemical properties under different levels of irrigation water salinity, a field experiment on clay loam soil was done as factorial with basic block design in four levels of irrigation water salinity (0.79, 5, 10, 15 dS m-1) and treatments of super absorbent (0.02 Kg m-2), vermicompost (1.5 Kg m-2) and without amendment. After irrigation and passing three months, soil electrical conductivity (EC), organic carbon content and pH were measured in three replications. Electrical conductivities (dS m-1), organic carbon (%) and pH for the without amendment plots were 4.24, 1.99 and 7.84, for the plots treatment by vermicompost were 3.68, 2.17 and 8.05, and for the plots treatment by super absorbent were 4.18, 1.98, and 7.97, respectively. The results showed the organic carbon and pH were significantly increased and soil EC was significantly decreased by treatment. The super absorbent increased the pH and decreased the EC significantly, but it had no significant effect on soil organic carbon. Soil electrical conductivity and organic carbon retention were significantly increased and soil pH was decreased by increasing water salinity. Overall, vermicompost showed better performance than super absorbent, because it decreased soil salinity in high water salinity and increased soil organic carbon.

One of the most important problems in agriculture is continuous decreasing in quality and quantity of water resources. One of the proposed solutions in the field is deficit irrigation and use of shallow groundwater. This study was conducted to assess the participation share of the shallow groundwater in supplying the water requirement of maize plant. Treatments comprised nitrogen fertilizer (N1, N2 and N3 with values of 450, 375 and 300 kg ha-1, respectively) and irrigation (I1, I2 and I3, with the amounts of 100, 75 and 50% of water requirement, respectively) with a fixed groundwater level at the depth of 70 cm. The results showed that raising the two main treatments levels significantly enhanced the properties of grain yield, dried matter and harvest index. The highest rises in grain yield and dried matter were 6.049 and 15.430 ton ha-1, respectively, which were obtained from the treatment I1. The grain yield was observed 12% increasing with rising nitrogen levels from 300 to 450 kg ha-1. The results showed that the grain yield increased 16% in the presence of water table in comparison with the free drainage conditions. Also, evaluation the results of the groundwater contribution in evapotranspiration showed that the maximum and minimum amounts involved were 31.4 and 5.78%, which were obtained from I3 and I1, respectively. Therefore, using shallow groundwater in spite of reducing the water drainage as well as environmental pollution, causes supplying the part of crop water requirement.

Assessing of soil genetically evolution is very important because the large number of management decisions depend on soil classification and its evolution rate. In this regards, evaluation of soils clay is one of the best indices for soil evolution. This study was carried out in four regions of Maraghe, Tabriz, Arasbaran and Amol by study of Alfisols, Mollisols and Aridisols with argillic horizon. The main aim of study was evaluation of soil evolution using quantitative and semi quantitative methods of CAI, MISODI and MISECA indices besides previous assessment of their evolution according to soil classification and micromorphological observations. Results revealed general description of soils evolution by CAI, while micromorphological indices especially MISODI describe accurate and rational studied soils evolution arrangement. The reason for accurate and rational description by MISODI index was the high number and precise parameters that according to this index evoluation rate increase in the studied soils of Mollisols, Alfisols and Aridisols orders respectively. Generally it can be concluded that regardless of achievable physical and chemical indices of soil evolution which may have errors and are private for each soils, quantification of soil microscopic studies can be the best way for soil evolution evaluating and determining their taxonomic distance.

In this study, the values of ET0 were estimated using the Penman-Monteith method for nine stations located in Lake Urmia basin over the 1986-2010 period. In order to detect the trends of reference crop evapotranspiration (in monthly, seasonal and annual time scales) the non-parametric Mann-Kendall (MK) statistical test was used. The Sen's estimator was used to evaluate the trend line slope of time series. The results showed that in the annual time scale six time series (66.6%) had significant (p

The purpose of this study was to cluster the observation well networks in Marageh Plain in East Azarbaijan and to predict the groundwater level by artificial neural networks. Primarily, by Hierarchical WARD clustering method, 20 observation wells of Maragheh Plain with over 15 years data period were clustered. Then, a cluster with 3 homogenous subclusters was selected and the representative of each subcluster was determined. Artificial neural networks with a multilayer perceptron structure utilizing back-propagation algorithm was used to simulate the representative groundwater level of each subcluster. The results indicated considering monthly temperature data as input for the artificial neural networks caused disorder of the network while considering lag time for the input data increased the accuracy of the estimated groundwater levels. Based on the results, the minimum and maximum RMSE between the observed and calculated values were 0.26 m and 0.63 m, respectively. Also the Maximum and minimum quantities of R2 were 0.86 and 0.82, respectively.