WATER AND SOIL SCIENCE (AGRICULTURAL SCIENCE)
Year:2015 | Volume:25 | Issue:3|Papers Count:22

Bandal like structures are used in the Indian Sub-Continent like Bangladesh as a local structure to maintain the navigability of the channel in alluvial rivers. This structure is a new type of spur dike with is made as a combination of permeable and impermeable spur dike. Local scouring in the nose of this structure is a designing problem of it that happens because of section constriction and strong vortexes. So determination of scour depth in designing of this structure is very important. There are few researches on Bandal Like spur dike, so in this research effect of spur dike permeability on maximum depth of scour hole around it was investigated. The experiments were conducted clear water conditions with the main variables of permeability percentage (4 cases) and four different discharges. For all experiments the spur length (L) and spurs relative spacing (S/L) were kept constant as 20% of the flume width and 3, respectively. The results showed that the maximum scour hole depth for the impermeable spur was much higher than that for Bandal Like. The minimum and maximum reductions on relative scour depth for Bandal Like spurs in comparison with the impermeable spur were calculated as 34.16% for permeability of 30%, at Froud-Number of 0.24 and 94.82% for permeability of 64%, at Froud-Number of 0.18, respectively.

One of the essential prerequisites for improving water consumption management in a farm is the accurate estimation of the crop water consumptive use. Accurate estimation of the consumed water by the crop evapotranspiration is one of the important factors in planning for agriculture development and increasing agricultural production. The FAO Penman- Monteith (FPM) method has been proposed as a universal standard method to estimate the reference crop evapotranspiration (ETo) and to evaluate the other procedures of ETo estimation, which needs solar radiation, wind speed, air temperature and relative humidity data. Unfortunately, there are no facilities for measurement of some weather parameters at some weather stations. Therefore, identifying the correctness of the ETo estimation methods by using the estimated climatic data is very important. Based on this, the objective of the present study was to evaluate the performance of the FPM method for estimating ETo when solar radiation (Rs), vapor pressure (ed) and relative humidity (RH) data were not available under climatological conditions of the northwest of Iran. Data of Urmia and Tabriz stations were used to compare the estimated ETo by the FPM method for the complete and limited data sets. The results showed that when RH and ed data were missing, the FPM method was still a very good option for estimating ETo in Urmia and Tabriz stations, with RMSE value smaller than 0.4 mm day-1. When Rs was missing, the FPM method was not good enough for estimating ETo, and RMSE increased to 0.7 mm day-1. The results also showed that solar radiation was the most effective parameter on ETo estimation and both vapor pressure and relative humidity had the same effect on ETo estimation.

One of the most important problems in water resources management is the optimal operation of dam reservoirs. Various methods have been applied to deal with optimization problems. Noting the inability of the conventional optimization methods to solve complex optimization problems, the Meta-Heuristic algorithms have been noticed more than ever. In this study, particle swarm, genetic and continuous ant colony system algorithms were used to optimize the operation of the Doroodzan reservoir. Furthermore, the effect of chain constraints inclusion on the framework of these algorithms were analyzed. The results indicated that regarding the chain constraints, all programs resulted in feasible solutions, where without chain constraints, in some cases the algorithm was unable to find a feasible solution. Therefore, applying these constraints in the framework of the algorithms improved their performances further. In finding the optimized solution, the Genetic algorithm had a better performance than the two other algorithms. Reliability criterion was used to evaluate the algorithms performances. Based on this criterion, as one of the most important criteria in determining system performance, the Genetic algorithm with the Reliability value of 0.964 had the most suitable performance.

Prediction of local scouring at downstream of hydraulic structures is one of the subjects which has been paid attention by researchers in recent years. In this study, the effects of shape of broad- crested weir with side slopes at different Froude numbers on local scouring were investigated at different particle Froude numbers. Firstly, the main factors affecting the process of downstream scouring were detected and adjusted as dimensionless parameters using dimensional analysis. Then variation of the sizes of scour hole dimensions were investigated by changing the lengths of weir crest and the horizontal apron, downstream slope of the weir at different particle Froude numbers. The results showed that the effects of weir crest length and the angle of downstream slope on scour hole depended on particle Froude number, while the scouring was less affected by particle Froude number with changes of the length of horizontal apron. Meanwhile, it was confirmed that there was a similarity between the various profiles of the scour. The parameters of the scour hole were presented as the dimensionless graphs that could be used in structure design to protect the bed against scouring.

Accurate forecasting of the daily discharge plays a significant role in the efficient management of water resources. For this purpose in order to model more accurately the process of forecasting the daily discharge of Nooranchay river in Atashgah basin, the artificial neural networks model (ANN) was used. In addition, in order to increase the accuracy of ANN, the principal component analysis (PCA) was used for preprocessing of input data. Finally, the results of multivariate linear regression (MLR) model were compared with the obtained results in the mentioned hydrological simulation. The results indicated that the hybrid model of ANN-PCA in comparison with ANN and MLR, had the highest precision. So that the results of goodness-of-fit tests criteria, such as the correlation coefficient (CC), the efficiency coefficient (EC) and the root mean square error (RMSE) for the hybrid model of ANN-PCA (at the verification stage) were CC=0.9959, EC=0.9905 and RMSE=0.0071, and for the ANN (at the verification stage) were CC=0.9093, EC=0.8269 and RMSE=0.0405 and the results for the MLR were obtained as CC=0.8866, EC=0.7860 and RMSE=0.0926. Also the use of PCA as an effective method for preprocessing of data, created independent components which eliminated the multicollinearity. Therefore, the PCA increased the efficiency of the ANN.

Water, oxygen, temperature, and mechanical resistance are the soil physical factors that can directly influence plant growth. Under favorable temperature not only sufficient water is available for the plant at the last limiting water range (LLWR), but also the other two factors are not limiting for the root activity. In order to study the corn single cross (Zea mays L.) response to the soil water content with reference to LLWR, a greenhouse experiment was conducted. Topsoil with clay loam texture was passed through 4.76-mm sieve, and transferred into PVC cylinders (diameter 15.2 cm and height 50 cm). The soil columns were compacted to achieve two levels of bulk densities (1.25 and 1.6 g cm-3). With three soil moisture levels (the LLWR range, less than its lower limit and greater than its upper limit), two compactions and three replications, 18 soil columns were prepared. Three corn seeds were planted in each column. After seedling emergence and thinning them to one plant per PVC pot, soil water treatments were applied at 5-leaves growth stage. Plant traits including plant height, leaf area, leaf relative water content and stomatal conductance were measured. The difference in these traits between the three soil water levels were significant (p<0.01). Increase in bulk density decreased LLWR (v/v) from 18% at 1.25 g cm-3 to 6% at 1.6 g cm-3. Mean values comparisons of the plant traits at both bulk densities showed that the soil water range defined by LLWR led to the highest values of the traits. Therefore, the thresholds values corresponding to air-filled porosity of 10%, permanent wilting point of 1.5 MPa suction and mechanical resistance of 2 MPa (as defined in the LLWR concept) were verified for the corn growth in the examined soil.

Sewage sludge contains relatively high amounts of salts and organic matters which may affect the physical and chemical characteristics of soil. In this study the effects of adding the urban sewage sludge on soil water repellency and water retention curve were investigated. A clay loam soil was picked up from Foladshar, Isfahan, a region at the vicinity of a sewage treatment system. Different amounts of urban sewage sludge (25, 50, 65 and 80 percent) were added to the soil and designated by S25%, S50%, S65% and S80%. Then water repellency of them was determined by means of water drop penetration time (WDPT) and molarity of aqueous ethanol (MED), after 50 days of incubation. Sludge addition resulted in low to severe water repellency of the soil samples. The water retention curves were determined by means of the pressure membrane and sand box apparatuses. Finally, sewage sludge effects on van Genuchten equation's parameters were assessed by using SAS8 software and Fisher test. There was a linear and positive correlation between the logarithmic values of WDPT and organic matter quantities. Furthermore, a linear regression was established between the values WDPT and MED with R2=0.95. The S80% treatment had higher θs while S0 had lower θs, because of higher organic matter in S80% and lower organic matter and clay loam texture of S0. The residual water content in S80% was lower than those in the other treatments and the maximum of θr was observed in S0. The parameter α was higher in S65% and S80% than those in the other treatments with slight water repellency which showed lower air entry value of the soil. The parameter n increased by increasing the organic matter in S25% and S50% rather than that in S0, but it decreased in S65% and S80%. This could be due to existence of higher water repellency and hydrophobic material on the surface of soil particles in S65% and S80% than those in the S25% and S50%. So intensive water repellency perhaps affected the parameter n and caused it to reduce it. Also water repellent soils had higher gravitational and available water than those in the primary wettable soil.

The objective of this study was to investigate the in situ stabilization of lead in a contaminated soil in the precense of P. A complex soil sample from 0-5 cm depth of the road side of Tehran-Qom was collected. In order to study the effect of P-treatment on the in situ stabilization of lead, a factorial experiment based on completely randomized design with three treatments of Diammonium phosphate (DAP), Triple Superphosphate (TSP) and 1:1 ratio acid phosphoric and phosphate rock at 3, 6 and 9 molar ratios of P/Pb, was conducted. Results of variance analysis and average comparison showed that among three phosphorous treatments, the highest transformation of soil Pb from the non-residual fractions (SS, SE, CA, Fe-Mn form and Pb in OM) to the residual fraction occured in DAP treatment and the lowest one in acid phosphoric and phosphat rock (P<0.01) treatment. Also results showed that the acid phosphoric phosphat rock, TSP and DAP could transform 18.3, 21.4 and 33.1% of the total nonresidul fractions into residual form. Results of X-ray Diffraction (XRD) analysis and comparison of treated soil with control, showed that adding phosphorous to soil resulted in the formation of pyromorphite mineral and DAP showed the highest peak intensity among three treatments.

Electrokinetic removal of heavy metals from contaminated soils (especially in soils with low hydraulic conductivity) is an innovative approach for their remediation. In this research, electrokinetic remediation of clayey loam soil spiked with Znwas evaluated in three depths 0, 15 and 30 cm at field-scale. All experiments were imposed with a constant voltage gradient of 1 Vcm-1 in three time periods of 2, 4 and 6 days at a field in Marand area, North West of Iran. The soil containedlarge amount of Zn (1575, 828, 965 mg kg-1 in 0, 15 and 30 cm depths respectively). The results indicated that the removal efficiencies for Zn were significantly influenced by time duration. For instance, the increment of the applied electrical current duration from 2 to 4 days increased the mean removal of Zn at 0, 15 and 30 cm depths 60.26%, 70.74% and 67%, respectively. The maximum metal removal efficiencies of Zn for the three depths of 0, 15 and 30 cm were 19.1%, 21.9% and 23.8% respectively. In addition, the pH changes along the soil plots showed an increasing trend of pH amount from the anode to the cathode.

Integrated water resources management is very important due to rapid population growth and limitation of water resources. There are different models for optimum water resources planning and management in a watershed area. In recent years the WEAP model has been used by many researchers due to its ability to consider the coupled physical-hydrological processes and the integrated water resources management systems as well as to prioritize water allocation. The main objective of this study was to use WEAP model for determining the amount of water allocated to industry from the Voshmgir and Golestan dams in the Gorganroud Basin (Golestan province). Thus, at first, the Gorganroud basin monthly flow was simulated and then the model was run for existing conditions and different scenarios. For this purpose, the “water year method” option in WEAP was used. In this model, sedimentation volume in reservoirs was incorporated by a cumulative manner as a dead storage at the end of each month. After modeling the Gorganroud basin with WEAP model, the allocated water volume percentages for agricultural, industrial, aquatic and environmental demands, considering the aims of project were obtained. The results showed that with the new allocation planning of the Gorganroud water resources, the water demand of the industry around the Voshmgir dam would be supplied up to 9.5 million cubic meters, accepting a 5% reduction in the system reliability. By ignoring reservoir sedimentation in modeling process, the system reliability reduced significantly. Moreover, considering 1 million cubic meters reduction in reservoir volume due to sedimentation every 5 years and increase of irrigation efficiencies, can preserve the system reliability in planning.

Total hardness (TH) of water causes numerous problems in life and industry, that shows the necessity of water hardness removal. In this research, different sorbents such as almond shell, wheat husk, rice husk, sawdust, zeolite, bentonite and activated carbon in raw state, acid-activated and alkaline-activated conditions for removing Ca, Mg and therefore, water hardness were used. The results of this study showed that some of sorbents needed to be activated by acid or base to remove calcium, magnesium and hardness of the brine solution in different salinities. In salinity of 20 dS m-1, acidic-activation of rice husk, sawdust, zeolites and activated carbon increased Mg removal from saline water. In this salinity, alkaline-activation of almond shell and bentonite and likewise acidic activation of wheat and rice husk enhanced Ca removal from saline water. Moreover, alkaline activation of almond shell and bentonite and likewise acidic activation of sawdust, wheat and rice husk caused reduction of saline water hardness. Removal percentages of calcium, magnesium and hardness for salinity of 9 dS m-1 were greater than those for the salinity of 20 dS m-1.

In most cases, it is observed that the statistical parameters values are not coincident with the moments of observed data moments. In the present study the data of water deficit in dry spells were extracted for the nine rivers located in the west basins of Lake Urmia from the daily flow rates data for sixty-day durations and these calculated data were used to the frequency analysis. In order to estimate the hydrological drought probability in the watersheds of the mentioned rivers, 12 common statistical probability distributions were tested. Using the Chi-square and the coefficient of determination tests between the observed and modeled data, the Log-Pearson type 3 was selected as the most suitable model among the used ones. In order to estimate the parameters of the selected distribution, the results of the methods namely maximum likelihood, ordinary moments, sundry average method and applied moment method based on the logarithms of the observations, were compared. The results showed that the accuracy of the sundry average method was more than those of the other used methods. The average value of the root mean square error statistic for the mentioned method was 0.855 m3/s.

Reduction of water resources and low efficiency of irrigation networks makes it necessary to pay attention to the management methods and the proper operation of the irrigation canals. In each irrigation network, there is a large number of offtake and cross-regulators that any change in their operating situation affects the behavior of other structures and lead to decrease in the hydraulic performance of canals. The structural perturbation is formed under partial changes in the setting of offtake and cross-regulator, which causes variations of the design depth and water surface profile. Partial changes in the inflow of a canal discharge lead to hydraulic perturbation and variation in water surface profile. In this research, in order to investigate the influence of structural and hydraulic perturbation on the flow depth, the governing Gradually Varied Flow (GVF) equation was linearized by Taylor's expansion and an analytical equation was developed to calculate the water depth changes. Then, for various hydraulic conditions, the results of the numerical solution of the governing GVF equation and the developed analytical formula were compared. The results showed that the errors of the presented formula to calculate the water surface profile changes under structural and hydraulic disturbances were less than 4% and 3.8%, respectively.

In this research, using different deterministic and geostatistical methods including kriging, inverse distance, local polynomial and radial basis functions, the seasonal and spatial distributions of cadmium (Cd) amounts in groundwater were evaluated in the Hamedan-Bahar plain. To do this groundwater of 30 wells in the plain were sampled in four seasons i.e. summer and autumn 2002, winter and spring 2003. To analyze the seasonal and spatial elements of the quality of ground water, the geostatistical software ArcGIS version 10 was used. The performance criteria for evaluating the used methods were Mean Absolute Error (MAE), Root Mean Square Error (RMSE) and General Standard Deviation (GSD) using the cross validation method. The results showed that local polynomial, kriging (disjunctive and simple), kriging method (probability and indicator) and kriging (probability and indicator) were the best methods to estimate Cd in summer, autumn, winter and spring, respectively. Also, kriging (probability and indicator) for summer and autumn as well as Radial Basis Functions method for winter and spring were illustrated as unsuitable methods for estimating Cd. The interpreted results showed, the best approach adopted for a period of time could not be utilized for other seasons. Also cadmium concentration was high in the northern parts of the plain (summer season) and in the Northeast parts (spring season). This concentration was up to 2.0 micrograms per liter in autumn season, which was covering all the plain. The trend of increase in cadmium concentrations was observed from eastern parts to western parts of the study area in the winter season.

In most studies related to the prediction of soil water retention curve (θ(h)) by pedotransfer functions (PTFs), its drying branch has been worked out and almost no study has been accomplished in developing PTFs for the wetting branch. The latter is required for describing some important natural phenomena such as irrigation and infiltration. Therefore, experimental data presenting the wetting and drying branches were obtained by using respectively Shani field method and pressure plate apparatus in 24 diverse soils. The Brooks-Corey parameters were calculated by fitting the model to the experimental data for the both branches. Each parameter of Brooks-Corey model was regressed against various soil attributes by using of the multivariable curvilinear regression and appropriate PTFs were developed to predict the parameters for both branch. Statistical criteria such as modified index of agreement, relative root mean squares error, geometric mean and geometric standard deviation of error ratio were adopted for accuracy assessment of the PTFs. All the PTFs developed were non-linear multiple regression with R2 ranged from 0.80 to 0.90. According to soil attributes contribution to the developed PTFs, organic matter and bulk density appeared as the two dominant soil properties that played major role in shaping both drying and wetting branches of the θ(h) as well as the hysteresis. Results of sensitivity analysis also confirmed the importance of these two variables.

Average temperature increase because of climate change is considered as an important environmental problem of human for which many studies have been conducted in the recent years. In this study, trends of the average air temperature of the Southern half of Iran in monthly and annual time scales were analyzed using the non-parametric Mann-Kendall method. Data used were the average air temperature data of 14 synoptic stations, covering the period of 1971-2010. The Sen's slope estimator was used for estimation of the slope of the trend line. Results showed that in annual time scale, 11 stations (79% of the selected stations) experienced a significant increasing trend and only two stations (Birjand and Chabahar) did not show significant positive trend in air temperature series. The Shahrekord station showed negative (insignificant) trend. The most strong positive trend slope in the case of annual temperature belonged to the Kerman station, which was equal to 0.061oC /yr. In monthly time scale, the numbers of months having positive trends were 13 times greater than those with negative trends. Except the Birjand, Chabahar and Shahrekord stations which experienced both negative and positive trends, the other stations only showed a positive trend. February and November had the most (all of the stations) and less (7 stations) numbers of stations with significant positive trends, respectively.

The scour around the bridge piers causes instability of them, and without applying an appropriate solution, it eventually leads to demolition of the structure. Therefore, study on the mechanism of the occurrence of the scour and effective parameters on the amount of scour are important. This study was preformed to find the effect of bridge pier’s dimension on the scour depth. Therefore, the tests were carried out for cylindrical bridge piers with diameters of 10, 20, 30, 40, 50 and 60 mm in clear water condition with relative velocities (water velocity over scour critical velocity) of 0.95, 0.86, 0.76 and 0.67 in a laboratory flume. The mean size of bed particles was equal to 0.51 mm. The results showed that with an increase of 13.15 percent in relative velocity of the flow from 0.76 to 0.86 for pier with diameter of 40 mm, also with an increase of 20 percent in the pier diameter from 50 to 60 mm at the flow relative velocity of 0.95, the scour depth increased 38.8 and 10.34 percent, respectively. In addition, by analysis of the experimental results, the pier with diameter of 40 mm was an appropriate one with suitable diameter so it was proposed for the other similar experiments.

One of the most important parameters in designing surface and subsurface drip irrigation systems is considering up and down soil wetting area of emitters. In this study, by means of Buckingham p theorem and using dimensional analysis, some equations were developed in order to estimate up and down soil wetted area of emitters. The experiments were carried out in a transparent plexiglass tank (0.5m.1.22m.3m) using three different soil textures (fine, heavy and medium). The drippers were installed at 4 different soil depths (surface, 15, 30 and 45cm). The emitter outflows were considered 2.4, 4 and 6 Lhr-1 with irrigation duration of 6hr. Then, using the-p theorem of Buckingham and dimensional analysis, equations were developed to estimate the up and down soil wetting area of emitters. The results of the comparisons between the simulated and measured values (evaluated correlation coefficient more than 90%) showed that these equations were very capable of predicting the soil wetting area. The average values of Root Mean Square Error (RMSE) for down wetted area (all depths) for the clay, loam and sandy soil textures were estimated as 0.015, 0.019 and 0.033, respectively which showed the relative superiority of the developed equations in the clay soil texture. Also, the average RMSE values for up wetted area in the same soil textures (0.02, 0.034 and 0.053, respectively) confirmed the equations accuracy. Considering these equations in designing surface and subsurface drip irrigation systems can improve these systems performance.

Analysis of extreme values based on a random sample is very important. Accurate forecasting of the extreme values is important in management and scientific scheduling to confront with deleterious aspects of water resources, such as flood, drought, etc. In the recent decades, application of statistical distributions in hydrology to obtain the designing data has been noted by many researchers. Many of the common statistical distributions (including some of the distributions used in flood-frequency analysis) such as the Generalized Extreme Value, Generalized Logistic, Generalized Normal, Pearson Type (III), Generalized Pareto distribution, and so on are the special cases of the four-parameter Kappa distribution. In this study, the regional analysis was used for fitting the above mentioned distributions to the annual peak flow data of the East Azerbaijan province. Using the L-moments technique, the whole province was divided into the four distinct regions (lack of discordant sites) and then regional parameters and quantiles of the mentioned distributions (including the Kappa distribution) were estimated. The results indicated that the Kappa distribution as a regional distribution was fitted well to the annual maximum discharges data.

Determination of fertigation criteria in new surface irrigation methods, especially furrow irrigation through surge flow, is necessary in order to increase water and fertigation use efficiency. Distribution uniformities of the water and nitrate are the most important indicators of the surface irrigation fertigation. For this purpose in this research, water and nitrate distribution uniformity indicators in furrow fertigation with surge and continuous flow regimes were evaluated using field experiments. The study was conducted in a soil with clay loam texture at the experimental station of the College of Agriculture and Natural Resources, University of Tehran in June, 2012. Fertigation management strategies in experiments with surge flow included injecting fertilizer during all advancing cycles, wetting phase and last advancing cycle plus start of wetting phase. Fertilizer injection for continuous flow was applied in the second half of advancing and wetting phases. Low quarter distribution uniformity of the nitrate in experiments with surge and continuous flow amounted to 54.4-93.8% and 77.7-93.6%, respectively. Also, low quarter distribution uniformity of the water for the same experiments amounted to 88.0-93.7% and 78.0-90.5%, respectively. Nitrate losses in all experiments were through runoff and its values in these experiments amounted to 5.1-47.1% and 3.7-27.2%, respectively. Low quarter concept was also used as an index for evaluating the water and nitrate application efficiency and distribution uniformity. The values of these indices for nitrate in experiments with surge and continuous flow regimes were calculated to be 45.0-80.5% and 68.2-79.5%, respectively. Overall, fertilizer injections in all surges and second half of advancing phase, respectively in furrow fertigation with surge and continuous flow regimes stand at the proper management practices for water and fertilizer.

Plain water balance is one of the most important issues from the view of water resource management and decision-making and planning of natural resources, agriculture and environment aspects. On the other hand, a survey of the water balance due to diversity of input and output components and uncertainties in the estimation of some environmental parameters makes the calculations extremely complex. Simultaneous evaluation of ground and surface water balance due to increases of input and output components in the field and watershed scales can intensify this complexity. The purpose of this study is to introduce a comprehensive and simple water balance equation, including all parameters of ground and surface water balance. In order to be able to analyze the data and determine outputs and inputs of Tuyserkan plain water balance, the data of precipitation and runoff as well as the primary base map data were collected. Initially, ground and surface water balance components were investigated separately, and then a comprehensive and simple formula was introduced to determine the complete plain water balance. The simplicity of the proposed equation is an advantage as the water balance components have been considerably decreased, (6 input components have been decreased to 3, including incoming surface runoff, incoming subsurface flow and precipitation and 5 output components have been decreased to 3, including evapotranspiration, outgoing subsurface flow and outgoing surface runoff). The presented equation seems to be applicable for other plains.

In order to protection of water quality in the aquifers, awareness about spatial and temporal distributions of water quality has particular importance. In this study, the spatial and temporal variations of water qualitative variables were analyzed based on the data of 47 selected wells in Tabriz plain over the period of 10 years (1382-1391). For the propose of spatial analyzing, the simple Kriging (SK) as well as the inverse distance weighting methods were carried out leading to derivation of isoquality curves for calcium, chloride, bicarbonate, potassium, magnesium and pH over the aquifer for each year. The study of annual spatial profiles extracted from isoquality curves for each qualitative variable showed that the majority of variables were aggregated on South West and North East part of aquifer. Using Ward method as a multivariate statistical cluster analysis procedure together with S statistics as a homogeneity test procedure, the homogeneous regions for pH were determined over the aquifer. Finally, the annual fluctuation in the qualitative variables were investigated, and according to the results, the majority of variables (except potassium) had incremental trend during the 10 years of statistical period.