نشریه دانش آب و خاک
سال بیست و سوم شماره 3 (پاییز 1392)

In this research، for the study of different landforms effects on soil micromorphological properties، five profiles at different physiographic units of lowland، plain، piedmont plain، river alluvial plain and hill were selected and sampled in Tabriz plain. The soils based on morphological، physical، chemical characteristics and keys to soil taxonomy (2010) were classified under orders of Aridisols or Entisols، suborders of Salids، Argids، Calsids and Orthents and subgroups of GypsicHaplosalids، Xeric Natragids، Xeric Haplocalcids، XerricTorriorthents. Also micromorphological observations showed that the effect of landforms or physiographic units on the formation of pedofeatures and clay coating were appeared around coarse particles in up-land soils with low development. Calcite microcrystals appeared in all profiles and refer to recent formation of the soils. Coarse to fine material ratios (c/f) were greater in up-land than in low-land soil profiles. Nodules and oxides of ferro and manganese were observed at the lower parts of most profiles. Angular blocky microstructures in lowlands were more developed than in upland areas، which describes an enaulic and porphyric distribution pattern respectively.

Rigid boundary channels are widely used as water conveyors in surface drainage، sewers and other systems. In order to do optimum and economic design، consideration of the movement of sediment particles is quite important. In this research، experimental data of incipient deposition and incipient motion of sediment particles are used. Applying critical velocity approach، new equations for incipient deposition of sediment particles in rigid boundary channels having circular، rectangular and U-shaped cross sections and also a new incipient motion equation for a V-shaped cross section are presented. These equations are compared with available equations given by critical velocity approach for incipient motion of sediment particles in rigid and loose boundary channels. The present research reveals the difference between incipient deposition and incipient motion، indeed. Herein، the effect of cross sectional shape on incipient deposition and incipient motion of sediment particles in rigid boundary channels are also considered. Analysis of the results using the estabilished equations for incipient deposition of the sediment particles in channels with different cross section shapes shows that rectangular channels require a lower critical velocity and U-shaped channels need a higher amount. This result clearly states the effect of cross sectional shape on incipient deposition for sediment particles in rigid boundary channels. Because of the lack of available data، the present analysis can be usefull for developing numerical models in rigid boundary channels.

In this study sensitivity of reference crop evapotranspiration (ETo) to the changes in meteorological parameters at two weather stations namely Sanandaj and Sabzevar were analyzed. For this purpose monthly data of meteorological parameters were used in the period 1964-2005. The amount of each meteorological parameter including mean air temperature، wind speed، actual vapor pressure and net radiation was changed in the range of ±20% and the corresponding change in ETo was calculated. This was accomplished either for the individual or for the combination of the parameters. Results showed that at both stations the maximum sensitivity of ETo belonged to Tmean، at both annual and monthly time scales. However، the less sensitive parameter in both time scales was actual vapor presuure. At the annual time scale، 20% increase in Tmean increased ETo for about 11. 23% and 12. 68% at Sanandaj and Sabzevar stations، respectively. However، 20% increase in ea decreased ETo for about 3. 29% and 3. 59% respectively at the same stations. At monthly time scale، Sanandaj ETo was less sensitive to weather parameters variations than that of Sabzevar station. In general، it could be concluded that at both stations the most influential parameter on ETo was the mean air temperature.

While flow over stepped spillway is in nappe regime، with gradual increasing of discharge and before changing flow to skimming، transition regime occurs. Different energy dissipation in each flow regime exists and thus understating of hydraulic conditions in the transition boundary of each regime is essential. The purpose of this research is to determine these boundaries among three regimes، their hydraulic conditions and specially governing hydraulic criteria on transition regime which have not been clarified in previous studies. For this purpose، 18 physical models of stepped spillways were built with slope angles of 15، 25 and 45 degrees. Results showed that transition regime depended on discharge and spillway slope. The boundary defined for the transition regime in this study is near the boundary proposed by other researchers، except with some shifting to the right. Comparison of the defined transition boundary in the present study with data of other researchers revealed greater reliability of the present study.

Sedimentation in dam reservoirs can have unfavorable effects on both dam and river. This phenomenon causes the reduction in useful volume of reservoirs، diminishing the dam stability، disorder in bottom outlets، intakes and penstocks function. To simulate the sedimentation in the reservoir، GSTARS3 software was used. To attain the optimum operation policy of the bottom outlets for minimizing the reservoir sedimentation، a computer program which had been written for this purpose was used. After calibrating this software for Voshmgir dam reservoir in Gorgan، the output results of running this software as a part of input data file were entered to an optimization model by an auxiliary computer program and after running the optimization model، results were converted to GSTARS3 as a part of the input data file by another auxiliary computer program. Then GSTARS3 was run again with the new data file which had been obtained from running the optimization model. The results of running GSTARS3 were transported to the optimization model once more. Data analyses accomplished in this cycle led to the desired accuracy. This problem of optimization is a constrained nonlinear programming and the penalty function method has been used to change it to a unconstrained problem. Then we used the continuous Genetic Algorithm (GA) method to solve the problem and operation of Voshmgir Dam.

Salinity and sodicity are of major problems of arid and semi-arid regions soils and account for lowering soil quality. In order to improve the physical and chemical qualities of these soils، a composite sample of a saline-sodic clay soil (ECe= 11. 5 dS/m، SAR= 13. 23) from Bilverdi agricultural research center of Islamic Azad University of Tabriz branch was collected. The experiment carried out in a greenhouse، was factorial with complete randomized design with 3 replications. The experimental factores (treatments) were a)polyacrylamide (PAM) (0، 0. 25 and 0. 5 g/kg soil)، b) pumice (0، 50 and 100 ton/ha) and c) municipal waste compost (0، 30 and 60 ton/ha). After complete mixing of these amendments with pre-wieghed amount of soils in plastic pots، the pots were kept in the greenhouse under 18-25 ◦c. The soil moisture varied in the range of 0. 5 FC to FC. Ten wetting and drying cycles were imposed to the pots using tap water with EC=0. 387 dS/m and SAR= 1. 014. After incubating of the pots for 100 days under the described conditions pH، saturated electrical conductivity (ECe)، sodium adsorbtion rate (SAR) and organic carbon (OC) were determinded in the disturbed samples taken from the pots. Saturated hydraulic conductivity (Ks) and slope of soil moisture curve at the inflection point (Si) were also determinded in undisturbed samples taken from the surface layers of the pots. Analysis of variance and mean comparisons between the treatments showed that pumice and compost reduced pHsignificantlyby 0. 37 unit in comparision to the control. Pumice and PAM also reduced ECe from 34. 9 to 43. 97 percent relative to the control. while compost raised ECe by 186. 69 percent relative to the control. The result clearly showed a positive effect of pumice and compost on reducing SAR by 58. 97 percent and positive effect of PAM and compost on increasing OC by 26. 67 percent in comparision to the control significantly. Due to strong adhesive effect of PAM for the soil particles، and thus its aggregation effect، this amendment led to more larger pores and as a result significantly raised Ks up to 3 cm/hr (638. 3%) and Si to 0. 074 unit (160. 87%) as compared with the control. Generally، it seems that using PAM at the beginning of saline-sodic soils reclamation may considerably facilitate the practice because it greatly improves hydraulic conductivity. Taking the benefits of pumice or compost will be the next step

Accurate forecasting of river flow is one of the most important factors in surface water resources management especially during flood and drought periods. Because of the importance of river flow forecasting، in this study، daily flow of Barandozchay river in two stations (Bibakran and Dizaj) for a period of 20 years using Wavelet Neural Network (WNN) which is a combination of wavelet analysis and Artificial Neural Network (ANN) has been predicted. The results of ANN model have been compared with WNN model. Data of the years 1990-2005 and 2006-2009 were used for training and verification of the networks، respectively. The performance of the two models was evaluated by statistics: r، RMSE and MAE. The results showed that the WNN model with a correlation coefficient of 0. 972 and 0. 976 (for stations of Dizaj and Bibkran، respectively) was able to forecast daily river flows better than the ANN model. Therefore، the results indicated that the proposed WNN method performed quite well compared to Artificial Neural Network method and could be applicable for river flow forecasting.

In this investigation، the effects of rice (Oryza sativa cv. Ali Kazemi) cultivation، sewage sludge compost and chemical fertilizers on changes in pH، EC، potassium and sodium in an alkaline soil solution after submergence were studied under greenhouse conditions. A factorial experiment based on randomized complete blocks design with two replications including duration of submergence at 10 levels (2، 11، 30، 37، 42، 49، 56، 63، 78، 92 days) and source and amount of organic and chemical fertilizers in six levels (control، 100% chemical fertilizers، 20g sewage sludge compost per kg of soil with and without 50% chemical fertilizers، 40g sewage sludge compost per kg of soil with and without 50% chemical fertilizers) and rice cultivation at two levels (cultivated and uncultivated) was carried out. The results showed that by increasing the duration of soil submergence، the pH of alkaline soil solution in the treatment with 100% chemical fertilizers increased، while in the treatments including 20 and 40g sewage sludge compost/kg of soil with and without 50% chemical fertilizers it decreased. In the all treatments، after submergence the EC of soil solution initially increased and after reaching a maximum decreased. In the all treatments، by increasing duration of submergence، concentration of potassium in soil solution decreased، while sodium concentration in soil solution increased. The pH of soil solution increased by application of chemical fertilizers while it decreased by application of sewage sludge compost. The EC and concentrations of sodium and potassium in soil solution increased by application of sewage sludge compost and chemical fertilizers compared to the control. At the end of growth period، the pH of soil solution in cultivated treatments (rhizosphere) was lower than that of uncultivated (non-rhizosphere) treatments. The effect of rice cultivation on the EC of soil solution was not significant while its effect on the concentrations of sodium and potassium in soil solution was significant.

Local scour around a bridge pier results from the flow and pier interaction and separation of the flow at the sides of the pier. One of the methods for a local scour countermeasure at bridge piers is the use of sacrificial piles. Sacrificial are piles placed upstream of a bridge pier for the purpose of protecting it from local scour by deflecting the high-velocity flow and reducing vortex system behind them. In this paper the effects of pile size and spacing between sacrificial piles are investigated in an experimental flume under clear-water condition. Uniform bed sediment with a median diameter of 0. 5 mm was used. The cylindrical pier was 40 mm in diameter (D). The sacrificial piles were of 32، 27 and 20 mm diameters (d) and the distances of the first sacrificial pile were equal to 2. 8D، 2. 95D، 3. 1D and 3. 4D from the upstream face of the pier. Three different flow rates were used، identified by V/Vc equal to 0. 67، 0. 81 and 0. 94. The results show that increasing flow intensity reduces the sheltering effect of the pile group. Also up to optimum distance، increasing the sacrificial pile diameter improves the effect of these piles، but for larger distances of the sacrificial piles the most efficient scour reduction occurs for the smallest sacrificial piles diameter. Furthermore، the experimental results show that when the sacrificial pile is located at a distance equal to 2. 95D of pier (X)، the significant scour reduction nearly to 39 - 121% will occur.

Soil erosion and sediment transport occur due to surface runoff and flow in channels and rivers. Sediment input rate into dam reservoirs not only decreases effective volume of reservoirs، but also has non desirable influence on intake structures، gates، stability and water quality. Thus، estimation of sediment transport input into reservoirs is an important factor. Due to complexity and effect of different parameters on erosion and sediment transport Phenomenon، the mathematical simulations of sediment transport have not enough accuracy. In this research، for predicting of solid inflow to reservoir of Shahriar dam firstly، sediment rating curve and classic methods are used. Then، the applicability of data driven and artificial intelligent approaches like feed forward، radial basis، generalized regression neural networks and neuro-fuzzy systems are evaluated. Results indicate the high capability and workability of neural network and neuro fuzzy methods and low accuracy of sediment rating curve and classic methods in simulation of sediment transport rate.

In addition to soil water content، soil matric potential is also important. Soil water characteristic curve (SWCC) describes soil water content and soil matric potential relationship. Many models have been developed to describe the SWCCs and their fitting to the experimental data. Their fitting accuracies in different soils، however، have been rarely investigated. In this study، 75 disturbed and undisturbed soil samples were taken from topsoils and subsoils of Guilan province and were partitioned into textural groups after textural measurements. Water contents were measured at 12 matric potentials. Thirteen well known and frequnetly applied SWCC models were fitted to the measured data. The most accurate models of total soil samples، each textural group and each textural class were determined using root mean square error، coefficient of determination and mean error. The Brooks and Corey، Kosugi and Gardner models had the least accuracies among all of the models. The results showed that Fredlund-Xing and Dexter models had better fitting accuracies than the van Genuchten model for total soil samples، textural groups and some of textural classes and showed superiority for the soils of Guilan province. Since، there was no significant difference between the fitting accuracies of the Fredlund-Xing and Dexter models on the empirical data، so Dexter model would be superior to the other models for the soils of Guilan province because of its simplicity.

Scouring around bridge piers as one of important and effective factors in bridge damage is a kind of erosion around the pier that occurs due to the effect of complex vortex flows and generally، result is a trench around the pier of bridge. Many field and laboratory investigations of scour around bridge pier and foundations cause to give different equations for prediction of scour depth. But، results of these equations are not satisfactory. In this research، capability of artificial intelligence is evaluated for simulation of cylindrical bridge pier scouring using laboratory data of cohesive soil bed. Using FFNN (Feed Forward Neural Network)، RBF (Radial Basis Function)، GRNN (Generalized Regression Neural Network) neural networks and ANFIS، scouring depth is calculated for both of dimensional and non–dimensional data and then using sensitivity analysis، effect of all parameters on pier scouring is determined. The results indicate that the ANFIS model leads to better results than the RBF and GRNN models but it is not as robust as FFNN.

One of the strategies for improving the management of drip irrigation systems is considering the soil water redistribution in different directions (horizontal، downward، radial and upward) which can be of considerable importance. In this research، the wetting front and water redistribution in light-، medium- and heavy-textured homogeneous soils were evaluated in drip irrigation systems. Irrigation time was set to 6 hours and measurements continued until 68 hours after irrigation. Experiments were carried out in a plexiglass container with transparent walls. Emitters were installed at 15، 30 and 45 cm depths and discharge rates of 2. 4 and 4 L/hr were applied. Observations of water front in surface drip irrigation showed that the water redistributed more in horizontal and vertical directions for lesser emitter discharges than the highest ones، but the contrary was observed for subsurface drip irrigation. For the same emitter discharge، the largest depth showed less water redistributed in the horizontal direction but the contrary was observed for shallow depths. This could be explained considering the dry soil area above the emitters that is larger in the deepest location.

Abutments are used to protect erodible river banks. This structure is subjected to scouring due to flow convergence at the nose of structure. Therefore، countermeasure methods should be employed in order to prevent financial damages and life hazards. One of these methods is to use a slot. The main application of a slot is to deviate and change the down flow at the upstream region of an abutment. Also it reduces the power of vortices around the abutment. In this research، parameters such as depth، hole dimensions and time development of scoring process were measured around a vertical abutment. Operation of the slot was then evaluated at different height، depth، width and distance from the abutment nose and compared with unprotected abutment. The results showed that the models for which the slot was installed near the wall under the bed with the depth equal to the width of the abutment had the best performance. The amount of scour reduction for different models was 11. 8 to 43 percent.

Particle size distribution (PSD) is one of the most important soil physical properties consisting of the primary and secondary PSD. The purpose of this study was to investigate the relationship between the primary PSD (sand، silt and clay) and the secondary PSD at different scales of aggregates. Sampling was done from two soil layers of 0-10 and 10-20 cm at farms with different cultivation systems including wheat، barley، maize، alfalfa، fallow and tilled lands، with three replications. Each soil sample was divided into three subsamples (size classes) of 0-0. 25mm، 0. 25-1mm and 1-5 mm. Results showed that the cultivation system had significant effects (p<0. 01) on the secondary PSD. There was a negative significant correlation between the sand percentage and water stable aggregates (WSA) >0. 25mm، while the correlation was positive for the silt fraction. Moreover، clay content had no significant influence on the WSA>0. 25mm. The percentages of sand، silt and clay particles in all the aggregate classes were significantly different، so that with increasing the aggregates size، the sand fraction increased، while the silt and clay contents significantly decreased. The fine، medium and large aggregate classes consisted of 45. 5، 55. 9 and 60. 8 percent of sand، 36. 0، 27. 5 and 24. 3 percent of silt and finally 17. 8، 16. 6 and 14. 8 percent of clay، respectively. However، in the all classes، the content of sand was higher than those of silt and clay. In addition، with increasing aggregate size from 0. 25-1 mm to 1-5 mm، the percentage of WSA>0. 25mm increased، significantly. The results also indicated that in these two classes، the sand fraction had negative relationship with the WSA>0. 25mm، while the relationships for silt and clay particles were positive. The findings of this research revealed that although the content of sand was higher in larger aggregates، but sand particles led to aggregate instability، however silt and particularly clay particles improved aggregate stability.

Methods to control and reduce local scour are based on the scour mechanism. One of these methods is the application of collar around piers and using different bridge piers geometries. In this study eight different shapes of bridge piers were used with collar around them and the obtained scour depths and rates were compared with those of circular pier. The effect of airfoil shaped piers length was also investigated. The results showed that the airfoil shaped pier with relative length of 3. 85 was more effective than the other shapes of piers due to reduction of power of horseshoe and wake vortices and the maximum scour depth reduced 22% compared to the cylinderical pier. Furthermore، using a collar with a diameter two times greater than the pier diameter in the airfoil shaped piers decreased the maximum scour depth up to 80% in comparison with circular pier and the equilibrium time of scour also increased. Also، the airfoil shaped piers which were located in flow path in inverse direction، reduced the maximum scour depth in front of pier about 60%.

چكيده [English] For selecting the most proper formula to estimate sediment discharge، there is a great need to evaluate them for any river. In this paper، suspended sediment estimation formulae in Bazoft، Soolegan and Armand River using Analytical Hierarchy Processing (AHP) were investigated and at last the priority of each formula in three rivers was compared. Three formulae of sediment estimation; Chang-Simons-Richardson، Bagnold، and Toffaleti were applied in this research. For solving these formulae numerical methods were applied. Accuracy of each formula was evaluated using two statistics (R2، NS). In addition to the cost calculation of solving each of the formula، the suitable numbers of it’s input parameters were studied. At first، pair-wise matrix for each of the criteria was created and then by calculating the final weight for each formula the preference rank of it was determined for each river. Chang-Simons-Richardson formula with final weights of 0. 34، 0. 53 and 0. 43 for Armand، Soolegan and Bazoft rivers was proposed as suitable formula for sediment discharge estimation of the three rivers، respectively.

Media found in nature are heterogeneous and contaminant dispersion coefficient in such media may have spatial variations. In this study، dispersion coefficient is presented in constant and spatially-varied forms. The spatially-varied dispersion coefficient has been defined by means of three types of linear، power and exponential functions and each of them has been entered separately in the transport equation and the obtained models are solved using the initial condition and Dirichlet boundary condition. For comparison of the models results، data of the continuous injection of sodium chloride ions in a 12. 5m column containing different soil textures have been used. Concentration-location curves at different times showed that at early times after the injection dispersion coefficient of the linear model was more compatible with the experimental data and that of the power model was less compatible with them. With elapsing time، results of the power model were better than those of the two other models. In general، with increasing time the similarity between the results of models and experiments was reduced. By fitting dispersion coefficient values obtained from the experiments at different points of the column length، the coefficients of determination for the linear، power and exponential models were estimated as 0. 501، 0. 856 and 0. 714، respectively. This showed that power and exponential models had better estimation than the linear model. At all times، results of the constant dispersion coefficient model had less similarity with the experimental results than the other models.

In order to investigate interaction of drought stress and potassium application on potassium، calcium، magnesium concentration and oil of two species of canola and mustard، a factorial experiment based on randomized complete block design with three replications was conducted during two years (2007-2009) at Agricultural and Natural Resources Research Station of Zehak located in Sistan and Baluchstan province. Irrigation regimes in three levels (irrigation after 50، 70 and 90 percent depletion of soil available water)، potassium sulphate fertilizer in three levels (0، 150 and 250 kg. ha-1 K2SO4) and two species of Brassica napus (Hyola 401 Hybrid of canola) and Brassica juncea (landrace cultivar of mustard native of Indian) were allocated to experiment factors. According to the results two species showed different pattern of potassium and calcium accumulation in their leaves. Mustard contained a higher leaf potassium and calcium contents than canola. Under severe drought stress، leaf potassium and magnesium increased but calcium change was not significant. Increasing potassium application in the soil increased potassium and decreased calcium concentration in the leaf. Potassium application did not show any significant effect on leaf magnesium concentration. Hyola 401 showed higher seed yield، oil yield and oil content than landrace of mustard. Seed and oil yield increased but oil percent decreased with increasing drought stress. Potassium application caused increasing seed yield and oil yield in different levels of water availability in both species. Seed yield had positive correlation with oil yield، oil content and potassium concentration but its correlation with leaf calcium and magnesium concentration was negative. Based on the results of this experiment، it can be reported that equilibrium supply of potassium and moisture increased grain yield، oil production and absorb of mineral nutrients in both species and property variation in nutrients absorption efficiency in brassica genus can be used in breeding programs for drought tolerance.