WATER AND SOIL SCIENCE (AGRICULTURAL SCIENCE)
Year:2010 | Volume:20.1 | Issue:3|Papers Count:14

Intakes are applied to divert water for agricultural, urban and industrial uses and to produce electricity. Vortices may occur at intakes in the case of insufficient submergence. In order to prevent the occurrence of vortices and air entrainment in intakes, an adequate submergence is required. In this study, flow characteristics at intake system of Aydoghmush Dam were investigated at different hydraulic conditions using finite volume numerical method through FLUENT model. Results were compared with the physical model measurements. Intake system of Aydoghmush Dam consists of an intake tower which is 40 meters high. There are four intake levels in the tower. Flow characteristics in four cases (i.e. gates No.1 to No.4 at opening states) were investigated. Piezometric heads and velocity values were computed using FLUENT model. Minimum, maximum and average RMSE of piezometric head were 0.13m, 2.42m and 0.67m, respectively. Critical submergence through Knauss criterion for gates No.1 to No.4 at opening states was 3.96 meters in the normal condition. The results from both physical and FLUENT model indicated that the critical submergence would depend on hydraulic conditions in intake structure.

Seal formation increases penetration resistance and decreases infiltration rate and volume in soil during irrigation and rainfall. The objective of this study was to investigate the effects of four natural and synthetic organic conditioners on aggregate stability, penetration resistance and available water capacity in a sandy loam soil with weak structure under greenhouse conditions. Soil conditioners with two application rates including polyacrylamide (PAM) 0.25 and 0.5, cattle manure 12.5 and 25, vermicompost 2.5 and 5 and biological sludge 1.7 and 3.4 (all in g.kg-1 of air dry soil) were mixed with the soil and uniformly packed in plastic pans and PVC tubes with 25 cm height and 50 and 25 cm diameter, respectively. Both pans and PVC tubes were incubated at (0.7-0.8) FC moisture content and at temperature of 22±4oC for 6 months. Pans were used for undisturbed soil sampling in order to measure water aggregates stability (WAS) and available water capacity (AWC) at 7, 30, 60, 120 and 180 days. Penetration resistance (PR) was measured at the same times in the tubes. Both applied levels of PAM significantly (p<0.05) increased WAS compared to the control and other conditioners and the increase continued for 180 days. Both levels of PAM and manure significantly (p<0.05) decreased PR compared to the control. Conditioning effects of vermicompost and biological sludge on WAS and PR became insignificant. All of the conditioners at the second level of application significantly (p<0.10) increased AWC. According to our findings, application of 0.25 gkg-1 PAM because of its lower cost, and 25 gkg-1 manure for its availability would improve both structure and water holding capacity of the coarse-textured soils.

In order to study the effect of foliar application of boron and zinc on yield and some qualitative characteristics of two rapeseed (Brassica napus L.) cultivars, a factorial experiment was carried out based on RCBD with 18 treatments and 3 replicates during 2005-2006 at Zanjan Agricultural Research Station. Factors of the experiment were: spraying of in 3 levels including Zn0 (without spraying), Zn1 (spraying with 3 g ZnSO4/L), Zn2 (spraying with 6 g ZnSO4/L) and H3BO3 spraying including B0 (without spraying), B1 (spraying with 2 g H3BO3/L), B3 (spraying with 4 g H3BO3/L) and the cultivars were V1 (SLM046) and V2 (Talayeh). Zn and B foliar applications were done in two plant phenological stages (early stemming and flowering). During the growth season common agronomic practices were followed and grain yield and concentration of oil, protein, Fe, Mn, Zn, Cu and B of rapeseed grains were measured at harvesting time. Results showed significant difference between the treatments, so maximum grain yield of 4180 kg/ha was obtained from Zn0B1 in V1 cultivar. Concomitant application of Zn and B led to increase in their concentrations in the grain that is important from rapeseed fortification view of point. Therefore, regarding to beneficial effects of B on grain yield and joint application of B and Zn on the seed quality simultaneous spraying of boric acid and Zn sulphate with 2 g /L and 3 g /L respectively in early stemming and flowering stages may be recommended for the study area and the similar regions.

Flow routing is a mathematical procedure for predicting volume change, speed, and shape of a flood wave in a channel as a function of time which is of great importance in river engineering, flood control and hazard reduction, river conservation, and modeling of flow in weirs and reservoirs. The solution of flood routing can be carried out using hydrologic or hydraulic procedure depending on conditions and existing information. In this research, hydraulic routing was carried out using 4-point finite difference Muskingum method based on St Venant dynamic wave equations. Furthermore, Muskingum linear and nonlinear hydrological approaches were applied for the purpose of comparing results of the methods and the parameters of Muskingum models were estimated using least square errors procedure. Along the reach of Mehranrood between Lighvan and Hervi hydrometer stations using upstream input hydrographs (Lighvan station) and downstream output hydrographs (Hervi station) 3 flood events were selected for flood routing. In hydraulic routing procedure, output hydrograph was obtained using input hydrograph and hydraulic characteristics of the reach. Hydraulic characteristics used in this method were longitudinal slope, side slope, bottom width and length of reach. In hydrologic routing procedure, one of the input flood hydrographs associated with the related output one were used for estimation of linear and nonlinear Muskingum models parameters. The resulted parameters then were used to evaluate the goodness of fit of the models by application of the two other input and output flood hydrographs. Results showed that hydraulic flood routing using dynamic wave method (4-point finite difference Muskingum method) was more compatible with the observed output hydrograph than Muskingum hydrological methods. Weak efficiency of the linear Muskingum model was also observed in comparison with the nonlinear one.

Due to severe surface water limitation and extended drought periods in Iran, proper management of dam reservoirs has been considered as a major challenge in recent years. When the classical methods of optimization do not provide efficient and sustainable results, the improved harmony search algorithm (IHS) can be applied. In this research, the proposed method has been used to manage Dez dam reservoir operation. A comparison between IHS and non linear programming (NLP) results show that the IHS reveals no decrease in convergence speed in spite of using a large set of simulation procedure. In most observed cases the responses of IHS were much better than that of NLP. Accordingly, the proposed method can be applied in reservoir operation system with success.

Regarding to problems that may arise during optimization of all parts of an earth dam simultaneously, it is more convenient to optimize each part separately by considering the effects of other parts on it. In this research, a new program for optimal geometry design of the clay core in embankment dams was proposed. This program leads to desired design with minimum volume of core materials. A genetic algorithm was employed to fulfill the design. The algorithm, judiciously searches for optimal design within the problem space. While the algorithm searches for optimization, some constraints such as seepage, hydraulic gradient and safety factor of stability are considered. In order to determine the values of these constraints through different kinds of designs, the new simple models were used. These models were obtained by linear regression approach. The results shows that regression models have successful operations and a general optimal plan design of core can be achieved for embankment dams.

Estimating air temperature is one of the important issues in agricultural planning and in water resources management which can be accomplished by using different methods such as empirical, semi-empirical and intelligent methods. In the present study, Adaptive Neuro Fuzzy Inference System, Artificial Neural Networks and Genetic Programming were used to estimate air temperature in the synoptic station of Tabriz City, northwest of Iran. Considering the statistical indices, all three models were able to estimate accurately minimum, mean and maximum air temperature. In spite of slight differences in the prediction accuracy and errors by the models, Adaptive Neuro Fuzzy Inference System, Artificial Neural Networks and Genetic Programming were in the order of priority. Also explicit solutions that show the relation between input and output variables are presented based on Genetic Programming. This adds to the superiority of Genetic Programming over the other two models.

Spillways are structures used for releasing the surplus floodwater in necessary conditions from storage dams. Side spillway is one of the most common and complicated structures. In this research, hydraulics of the flow in the physical model of flood control structure for Vanyar dam which consists of side spillway, lavok, transition, ogee spillway and chute is three dimensionally simulated, using fluent numerical model and the results consisting of flow depth and hydrostatic pressure at 110 points were compared with experimental data. For flow analysis, k-ε model for turbulence and volume of fluid (VOF) model for multiphase flow simulation were applied. The analysis of turbulence parameters in lavok channel and boundary layer development on chute was also provided. Results show that there is a good agreement between numerical and experimental results, especially standard k-e model for hydrostatic pressure and RNG k-e model for water surface profile.

In order to evaluate performance of the center pivot irrigation systems, an understanding of water application characteristics of these systems is necessary. A new model and its computer program are developed to calculate applied water depth and coefficient of application uniformity of center pivot systems. The model uses water distribution pattern of stationary single spray nozzle as an input and simulates center pivot overall water distribution pattern. For this purpose, two static and dynamic square grids are considered. The static grid is obtained by dividing irrigated field to square components. The dynamic grid is resulted from adapting a grid with square components on water distribution pattern of single spray nozzle and is moved with moving spray nozzle on the center pivot lateral. Dynamic grid is moved over static grid. Water depths received in the field are determined in static grid components via considering water applications rates in dynamic components. Distribution patterns are overlapped in areas covered by adjacent spray nozzles.  The model outputs are water depths received in the field in all components of the static grid and water application uniformity coefficient. In order to evaluate and validate the model performance, several experiments were conducted in the field and the model was run for the same conditions. The results showed high accuracy of the model in simulating water distribution patterns of the center pivot irrigation systems.

Change in atmospheric greenhouse gases Leads to imbalance between different elements of the earth climate. However, the amount of the gases that will be disposed in to the atmosphere in the future by human activity is uncertain and may be presented under different scenarios. In this study, the daily time series of climatic parameters for Ruddasht region (located in Esfahan Province, Iran) under A2 (857 ppm CO2., 308oC temperature rise) and B1 (538 ppm CO2., 2oC temperature rise) climate change scenarios were generated for the period 2011-2030 using HADCM3 Global Circulation Model (GCM) and LARS-WG weather generator. The results showed that, in the region of study, the amount of mean total yearly precipitation, mean total effective precipitation and mean daily temperature would increase under climate change scenarios. The effects of climate change on irrigated wheat yield were analyzed using SWAP model. The analysis of relative and actual yield of wheat under different climatic scenarios showed that the mean relative yield under scenarios A2 and B1 would decrease by 1.49 and 2.1 percent and the mean actual yield would decrease by 4.19 and 17.9 percent, respectively. Analyzing related risks of yield decrease demonstrated that the risk of yield reduction would increase in climate change scenarios. The risk of 500 kg.ha-1 wheat yield reduction in comparison with base scenario (BS) mean value were estimated 7, 15 and 55 percent for BS, A2 and B1 scenarios, respectively.

Saffron plant with high value of economic rank has an important role in the non-petroleum Iran's foreign exports. Consequently, identifying of suitable areas for expansion of saffron cultivation could be an important task in Marand County, northwest of Iran. In addition, understanding the role of existing environmental factors in growth of saffron needs a comprehensive study and variety of spatial information as well as the associated attributes. With the help of GIS it is possible to supply such information and also to set up different kind of spatial analysis based on renowned models. In this work based on the saffron ecological and environmental requirements, one of the well-known Multi-criteria decision analysis (AHP model) was introduced in ARCGIS software setting. Modelling processes such as statistical and mathematical analysis of the data was sequentially pioneered and the suitable areas for saffron cultivation has been investigated. The results showed that the AHP model is a sufficiently appropriate approach for the evaluating of suitable lands for saffron growth and development throughout Marand County geographic extent.

Knowledge of variation of suspended sediment due to sudden and gradual fluctuations of river discharge is one of the important subjects in water studies specially watershed management. For this purpose sediment hysteretic loops based on hysterics theory have been utilized for last decade. Due to lack of such studies in Iran, this study attempts to investigate variations of suspended sediment hysteretic loops of 13 runoff events along 4 years for the first time. Therefore, after simulation of instantaneous suspended sediment concentration using Artificial Neural Networks and regression methods, hysteretic loops of suspended sediment plotted based on the best method from which 6 cases of single valued, 4 cases of eight-shaped, 2 cases of clockwise and one case of counter-clockwise were observed. The results showed that the linear hysteretic loops occurred in spring were because of low intensity precipitations and the 8-shaped loops mostly occurred in dry season with low river discharge and intense precipitations.

The subsurface drainage system as a part of irrigation and drainage network of Abadan palms date field, was evaluated regarding drain outflow rate and its effect on water table fluctuations, using the Drainmod model. Through statistical analysis of values measured on the farm, and water table depth predicted by the model, standard error (S) and the average absolute deviation (a) for the years 2003-7 were obtained 6.99 and 6.33 cm, 8.94 and 8.42 cm, 8.21 and 7.82 cm, 9.2 and 8.82 cm, 9.18 and 8.93, respectively. These values indicate the suitability of project’s subsurface drainage system regarding its effect on water table depth fluctuations. Additionally, by statistical analysis of values measured on the farm and drain outflows predicted by the model, standard error (S) and average absolute deviation (a) for the years 2005-8 were achieved 1.7 and 1.43, 1.38 and 1.3, 1.13 and 1.07, 1.52 and 1.37 mm per day, respectively. These values reveal suitability of the project’s subsurface drainage system regarding its effect on drain outflows. Furthermore, considering present irrigation planning of Abadan palm date fields, water table depth fluctuations and drain outflows were predicted for 2010 using of Drainmod model. It was found out from the results gained in the present study that subsurface drainage system of Abadan date palms is appropriate not only with respect to drain outflows but also to its effect on water table depth fluctuations, because by controlling water table, it will provide palm trees with suitable conditions for growth.

One of the important factor for development in each region is the availability of appropriate water resources. In addition to water quantity quality is also of great importance. The aim of this study is to medel the qualitative indices (BOD, DO) of river water using multi-layer perceptron neural network. In this paper, the information and data from Morad Beik river of hamadan including 10 monthly parameters of water quality in a one-year period and at six stations were used to predict biological exygen demand (BOD) and dissolved oxygen (DO), as indices affecting water quality. Efficiency of the neural network model was evaluated by some statistical criteria including correlation coefficient (R), root mean square error (RMSE) and mean absolute error (MAE). In the optimum structure of neural network the correlations coefficient for BOD and DO were 0.986 and 0.969, and root mean square errors were 8.42 and 0.84 respectively. The results indicated the ability of multi-layers perceptron neural network as a suitable technique for simulating changes in BOD and DO indices.