Journal of Water and Soil Conservation
Year:2013 | Volume:20 | Issue:4|Papers Count:16

Estimation of groundwater in the aquifer water resources management is important. In this study for estimation of the spatial distribution of water table level in Hamadan-Bahar plain neural intelligent methods including Multy Layer Perseptron (MLP), Radial Basis Function (RBF), Co-Active Neuro-Fuzzy Inference System (CANFIS) and Adaptive Neural Network based Genetic Algorithm (ANNGA) were used. To estimate water table in locations without measurements values, point values were estimated from each neural intelligent methods zoned in geographic information system. Overall, accuracy of used method based minimum errors were related to ANNGS, MLP, RBF and CANFIS, respectively. So that in ANNGA model, Root Mean Square Error (RMSE) was 0.431 m and correlation coefficient (r) value was 0.996. Maximum errors were related to CANFIS and RBF models with RMSE=1.27 m and RMSE=0.81 m, respectively. Also, comparison of the spatial variation of water table estimated by ANNGA model with observational data showed that points distribution in 90% confidence limits were little. Therefore, with using the latitude and longitude as input data water table spatial changes and its zoning can be estimated.

Due to high variability and complexity of the soils, direct measurement of hydraulic parameters is difficult, time-consuming and expensive. Therefore, these properties are estimated using indirect methods. In this study, 74 soil samples were taken from Guilan province, and particle (PSD) and micro-aggregate size distribution (MASD), bulk density and water content at matric suctions of 2, 5, 33, 100 and 1500 kPa were measured. Fractal parameters of soil PSD and MASD and particle’s size distribution parameters of Fredlund’s model were calculated and used to estimate water content at different matric suctions. The results showed that entering fractal parameters of PSD did not improve the estimation of water content. By adding fractal parameters of MASD to the model, estimation of water contents at different matric suctions was improved significantly (P<0.05) and the root mean square error (RMSE) value decreased by 6.5% for the validation step. This may be the result of the influence of soil structure on water retention. But using of PSD parameters of Fredlund’s model was more effective in estimation of water content and decreased the RMSE of validation step up to 27.0%. The best estimation of water content was observed at the matric suction of 5 kPa, in which the coefficient of determination of training step increased by 0.36. It may be due to the large number of parameters of Fredlund’s model and better simulation of PSD. In general, using parameters of PSD and MASD improved the estimation of soil water retention curve.

Large areas of Iran are located in arid and semi-arid climatic regions and their soils are naturally subjected to erosion and degradation. Be aware of how management practices and topographic features influence soil organic carbon and aggregate stability is a very important issue from the land management point of view. In this study, four different land use management sites (preserved pasture, grazing pasture, overgrazing pasture and rain fed lands) positioned in the hill slopes of Sisab experimental station (Bojnourd) were considered. In each site, soil samples from 0-15 cm of summit, backslope and toeslope in north and south-facing slopes were sampled. Soil samples were analyzed by using standard methods. The results showed that sand content in south-facing slopes was higher compare to north facing slopes, while silt content, soil organic carbon and mean weight diameter (MWD) were higher in north-facing slopes compared to south facing slopes. The maximum soil organic carbon and MWD were observed in the toeslope of north-facing slope while the minimum were monitored in backslope of south-facing slopes. The results also showed that sand content increased to 41 and 39% in overgrazing and grazing pastures respectively compared to preserved pasture and clay content decreased by 6%. Soil organic carbon decreased from 9.6 (g kg-1) in preserved pasture to 6.4, 8.2 and 9.1 (g kg-1) in cultivated land, overgrazing and grazing pastures, respectively. MWD decreased by 55, 35 and 17 percent in rain fed, overgrazing pasture and grazing pasture compared with preserved pasture, respectively. Despite the strong correlation between MWD and soil organic carbon (R2=0.81) in all sites, the aggregate stability in north-facing slopes was mainly influenced by organic carbon while the role of calcium carbonate was notable in south-facing slopes.

Because stepped spillways can significantly reduce the depth and size needed for a stilling basin at the toe of a dam and lead to great economic benefit, these spillways are increasingly attractive in hydraulic engineering. It is commonly acknowledged that free-surface aeration is significant in stepped spillways. In this paper, for investigation of Mixture and VOF method's ability, air-entrainment in skimming flow over the stepped spillways is simulated by using Fluent software. The numerical simulation results of free surface, velocity components and air concentration in water and circumstance of air entry into the water have been compared with the experimental results. It was found, downstream of the inception point of free-surface aeration which rapid free-surface aeration is observed, free surface is simulated better by Mixture method. On the steps downstream of the inception point of free-surface aeration, the results of Mixture and VOF methods about velocity distribution are closer together (RMSE is equal to 0.25 and 0.23 for Mixture and VOF Methods, respectively). But on the steps located further downstream by a strong air entrainment, Mixture method gives relatively better results (RMSE is equal to 0.23 and 0.33 for Mixture and VOF Methods, respectively). Also in the Mixture method, convergence time is much less than VOF method. This time reduces about four to five times.

Due to the nature of permeability and economic consideration, Rock fill dam structures have been attracted by many engineers for flood relief pourpose. Knowledge of flow passing hydraulic is necessary for proper design of this structure. Due to the fact that most of former studies were based on no sediment laden flow, therefore the mechanism of sediment laden flow in this structure is studied experimentally. The experiments were conducted in a recirculating flume with various bed slope (i.e 0.001, 0.005 and 0.01), feeding sediment size (0.4, 0.6 and 0.8 mm) and 4 porous media (2 fine media and 2 coarse media). By simulating the flow in rock fill dam with pressurised flow in pipes, the basic relation between f and Re is obtained in sediment laden flow condition. The results showed that the friction coefficient of sediment laden flow is higher than non sediment flow and the previous empirical relationship doesn’t give accurate estimates of Darcy-Weisbach factor in sediment laden flow.

Application of sewage sludge in agricultural lands is a suitable selection for solving management problems of sewage sludge, besides its economic benefits. Of the main limiting factors to use sewage sludge is its high content of heavy metals such as lead and cadmium. The aim of this study was to investigate the influence of natural Zeolite on lead and cadmium uptake by maize (Zea mays. L.) from sewage sludge. For this purpose, a factorial greenhouse experiment as a complete randomized design with four replications was conducted. Different levels of sewage sludge with 15, 20 and 25% (w/w) and zeolite with 0, 5, 10 and 15% (w/w) and an un-amended control pot were used in order to examine the sewage sludge influence. The results showed that the use of sewage sludge up to 20% rate leads to increase lead concentration in maize shoots, but this increase was statistically significant only in 20% rate of sewage sludge into control treatment. The use of sewage sludge leads to significant concentration increase of lead and cadmium in roots. The result showed that application of zeolite leads to significant decrease of lead and cadmium concentrations in shoots and roots of maize and significant increase of soil pH.

This study was conducted to evaluate CropSyst model to predict the fate and residual N of wheat production system in Gorgan-Northeast of Iran and to estimate N losses in different wheat management scenarios. Evaluation of CropSyst to predict N uptake and residual N in soil profile were performed using 16 local fields in Gorgan. Simulation of N losses in wheat production systems were conducted during 1967-2009 (40 years). Simulation scenarios were irrigated cultivation (average input; AI), irrigated cultivation (High input; HI) and rainfed cultivation (low input; LI). Results indicated that CropSyst model could satisfactorily predict yield, N uptake, residual N of wheat production system. Wheat yield of scenarios were 4400, 4500 and 4000 (kg/ha) for AI, HI and LI respectively that LI yield was significantly lower than AI and HI. Total N losses in AI, HI and LI were 13.5, 18.1 and 9.8 (kg N/ha) respectively. The highest losses of N had occurred by gaseous loss (45 to 63% of total N losses) in which volatilization (NH3(g)) contributed about 45 to 61% of total N losses and scenarios had significant differences. Nitrate leaching scenarios were not significantly different and it was about 3 kg N/ha. It can be concluded that application of urea as topdressing led to increase N losses (NH3 volatilization) and changing of the type of fertilizer and fertilizer management could reduce N losses.

Obtaining oil per day in Iran often caused its distribution and emission to the environment in various stages of operation and transportation. Efficient methods to clean up soil pollution, but environmentally friendly and suitable is inevitable. The aim of this study was optimization of total petroleum hydrocarbons (TPH) biodegradation by indigenous and non indigenous microorganisms in different applied remediation methods. Then, the best performance and trend of hydrocarbon contamination decomposition in time series were determined. Hence Ray's refinery contaminated soil with 38% TPH was used and thirteen treatments including fertilizers, animal manure, sawdust and inoculation of bacteria's (Bacillus subtilis, Bacillusmegaterium, Pseudomonasputida) were applied in soil thirteen times (every 2 weeks). The results showed that, treatments of bacteria + sawdust and bacteria had the greatest impact respectively with 35% and 34% decrease, of oil pollution of this soil and treatment of dry soil (without any additives except aeration) with a 20% reduction, had less effective in the amount of oil, than other treatments. The results indicated that, by active indigenous microorganisms and improving environmental conditions including aeration, additional nutrients and moisture, decomposition rate of petroleum can be increased. If native microorganism activity has low level, mixing sawdust, animal manure with inoculated non-native microorganisms including oil-eating active bacteria, will increase the process of reducing petroleum pollution.

Proper and organized use of natural resources can help preserve this valuable asset. Land use optimization science can be especially useful in this regard. The main purpose of the present study is to present an appropriate model for optimized allocation of lands with the purpose of gaining the minimizing surface runoff and sedimentation in Jajrood watershed. This watershed is located in the south of Tehran province, Iran. To determine the best land use combination, first the runoff amount in every land use was calculated, and then sedimentation was determined in every land use. Finally, the multi-objective linear programming model was used to solve the optimization problem based on Simplex Method. Results showed that the present land uses area was not optimized and require changes in existence land uses. The optimization results emphasize that the area of irrigated farming lands and rangelands should be reduced and orchards should be increased. The results also indicate that after optimization was employed, surface runoff decreased 73.03 percent and sedimentation decreased about 36.93 percent. The results of sensitivity analysis showed that total surface area of orchards and irrigated farming was the most sensitive factor to changes in runoff and sedimentation. In addition results showed that the most sensitive coefficient in runoff minimizing function is rangeland coefficient and in minimizing sediment function is irrigated farming coefficient, which is due to the high runoff and sedimentation rate of these two kinds of land uses.

Water flow and solute transport modeling in the vadose zone requires understanding of soil hydraulic properties such as soil water retention curve and unsaturated hydraulic conductivity. Direct measurements of these hydraulic properties using field and laboratory technique which are called the direct methods are costly and time consuming. Indirect determination of these properties using pedotransfer functions as suitable replacement for direct measurements has been of interest to researchers. Pedotransfer functions were commonly used to estimate drying branch of soil water retention curve in different study. Evaluation of pedotransfer functions to estimate the wetting branch of soil water retention curve has rarely been considered. In this study, accuracy of Rosetta and SoilPar software as well as pedotransfer functions of Rawls and Brakensiek and Saxton to estimate wetting branch of soil water retention curve and unsaturated hydraulic conductivity were studied and evaluated. Shani method known as dripper method was used to measure wetting branch of soil water retention curve and unsaturated hydraulic conductivity. Statistical criteria including RMSE, MAE and E' were used to compare the accuracy of the pedotransfer functions to estimate the wetting branch of soil water retention curve and unsaturated hydraulic conductivity. Results showed that simulated soil water retention curve using pedotransfer functions were not consistent with the measured soil water retention curve. Comparison statistical criteria values showed that pedotransfer functions of Rawls and Brakensiek which was used to estimate parameters of Campbell's and Brooks and Corey's unsaturated hydraulic conductivity models had approximately good yield than the others pedotransfer functions.

Pollution caused by crude oil and its derivatives is the most prevalent problem throughout the world, during its crude oil extraction, transport, refining and burning. Oil spills can have serious effects on human and other creatures. Therefore cleaning up environmental oil pollution is an alternative technique for physicochemical methods. The purpose of this study was to evaluate the biodegradation rate of fuel-oil contaminated soil by alfalfa (Medicagoscutellata) and grass (Poabulbosa) along with Pseudomonas putida bacterium. Thus, alfalfa and grass seeds were planted in two density levels with and without Pseudomonas putida in pots containing fuel oil-contaminated soil under greenhouse condition. Soil samplings were done in germination, vegetative and reproductive stages of plant growth. Results obtained in this study showed that both alfalfa and grass plants decreased fuel oil in the contaminated soil. The treatment of bacteria and the plants with high density had a positive effect in reducing the amount of soil hydrocarbon contamination. However, this reduction was not significant compared to treatments without bacteria and plants with less density.

Iron reduction in ferric minerals has an impressive role in bioremediation of organic and nonorganic contaminants and understanding the efficient factors in this process will be important. Organic matters are effective in bioreduction of ferric iron with different mechanisms such as electron shuttling and complexation. In order to examine the effect of simultaneous use of AQS (as an electron shuttling) and ferrozine (as a complexing agent) in bioreduction of ferric iron in hematite an experiment was conducted under laboratory conditions in the form of a completely randomized design with 24 treatments and 3 replications in the presence of Shewanella spp. Control treatments included 6 variable concentration of ferrozine (0, 0.5, 1, 1.5, 2 and 2.5 mM) and 6 variable concentration of AQS (0, 10, 20, 30. 40 and 50 mM) and compound treatments included variable concentrations of ferrozine with fix concentration of AQS (50mM) and variable concentrations of AQS and constant concentration of ferrozine (2mM). Produced soluble and acid extractable Fe (II) in compound treatments with variable ferrozine levels and constant concentration of AQS increased with increasing concentrations of ferrozine but in treatments with different levels of AQS and constant concentration of ferrozine didn’t show significant difference. Therefore, effects of both ferrozine and AQS were additive on bioreduction. However, none of these two compounds were solely dominant for increasing ferric iron bioreduction process in hematite.

Both of extra using of water resources and climate change (reduction of precipitation) have caused the shortage of water resources in Iran. In this case, management of ground water resources is important for agriculture and industries. Modeling and prediction of ground water table is one way for management of water resources. For prediction of ground water table ANN and time series techniques were used. Goal of this research is analysis of ANN and time series appropriately in prediction of ground water level. In this paper 35 water level of wells in Bakhtegan basin with monthly data from 1381 to 1389 were used. Water level of wells were predicted with ANN and time series (ARIMA) techniques and finally Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) for each of techniques were calculated. Results showed that ANN and time series techniques are suitable for prediction of ground water surface.

The dividing streamline can be defined as a portion of flow from main canals that entering intake channel. The dividing streamline extends far out into the main channel near the bed and stays near the main channel wall at the water surface and so a large portion of bed load can enter to the lateral intake channel. In this study four experiments include: submerged vanes with intake, spur dike with intake and using simultaneous spur dike submerged vanes in front of intake and without any structure in front of intake channel. Results showed that by using a set of vanes, the dividing to streamline move near intake channel near the bed and extend far out at the water surface. At discharge ratio of 0.18, width of the separation zone is 34 percent of main channel width and by using simultaneous spur dike and submerged vanes, it decreases to 4 percent. Furthermore, by adding a single spur dike to the set of vanes, the efficiency of vanes increases and also due to reducing the dividing streamline expansion to the main channel, sediment movement to lateral intake decreased.

Scour around bridge foundations is one of the major cause of serious damage to the bridge. In this study, the effect of foundation shape and level on scour process was investigated experimentally. The experiments were conducted for 4 foundations shape including; square, cylinder and aerodynamic along and across the channel and 4 foundation depths. The results showed that the scour depth depends on the foundation depth and shape. The best foundation shape which leads to minimum scour around it, were aerodynamic along the channel, square, aerodynamic across the channel and cylindrical shape, respectively. The results also show that by positioning the foundation below the initial channel bed, in addition to postponing in scour, leads to lower values of it. The scour depth also increases when the foundation level above the initial bed level increases. Analyses of results show that the appropriate location for positioning the foundation is 25 to 50% pier diameter.