مجله آبیاری و زهکشی ایران
سال هفتم شماره 2 (تابستان 1392)

Drainage water that flows to the subsurface drains is compound of irrigation water and salinity ground water that causes many environmental problems. In this study a physical model from Plexiglas was made to investigate effect of water table head on the mixing depth and drainage water quality. Mixing depth is the outer flow path under the tile drain. A saline water of K2MnO4 and NaCl were added to subsurface reservoir to simulate a ground water with 20 dS/m salinity. In the upper part of model a drip irrigation system was installed to apply water. Water table head is fixed by applying the constant irrigation discharge. The outer flow path was recorded on the Plexiglas side using a photograph. The results of this study indicated that by increasing the irrigation discharge, the water table head in midpoint and mixing depth increases, so salinity of drainage water increases. The relationship between mixing depth and drainage water discharge reports as a power function.Finally mixing depth was obtained as a parabolic equation. Mixing depth was introduced as a function of distance and water table between two drains. In comparison the salinity of drainage water with irrigation water the results showed that the great deal of drainage water is from ground water. Also the amount of salt that is carried by drainage water, after fixing water table head, is depended to water table head. The depth of leached zone with percolation flow increases when the water table head increases. It is advised to reduce installation depth of drains to decline water table and mixing water depth and prevent outflow of salinity of lower depths.

Drainage of agricultural lands is very important and without drainage a sustainable agriculture isn’t possible. In the absence of natural drainage in agricultural lands, artificial drainage is necessary. Construction of drainage ditches is one of the usual methods of artificial drainage. Study of the governing equations of flow to drainage systems is an interesting subject to researchers. In this study, an analytical solution for steady-state seepage of ponded water into drainage ditches is developed. The ditches are partly penetrating, parallel to each other and excavated by rectangular cross section in a homogeneous and isotropic soil layer. In order to derive the relevant equations of seepage quantities and velocities, first hodograph and complex potential planes were drawn with attention to the boundary conditions of physical plane; then the conformal mappings of physical and hodograph planes on auxiliary planes were found using Schwarz-Christoffel transformation. The chain rule was used to find the relation between complex potential plane and auxiliary plane. This method can be used to calculate the seepage quantities and velocities as well as ditches drainage designing. The results showed that near the ditches, seepage velocity along the ponded surface was very high as compared with that between the ditches, so leaching was non-uniform.

Based on the global presupposition, 52 countries will face water deficit crisis by 2025, therefore, it would be inevitable to use water resources efficiently and favorably. In this regard, fundamental and comprehensive changes in the current agricultural structure are vital, which is referred to as the largest water consuming activity, designing the cropping pattern in order to determine the cultivated area, proper rotation, and water use is of the great importance. In this study we aimed to present a model which could provide optimum cropping pattern, cultivation area, and allowable deficit irrigation during growing season, using genetic algorithms. The results showed that the model did not suggest deficit irrigation during the cultivation period, instead full irrigation was suggested. Furthermore, the result of sensitivity analysis indicated that by increasing the price of water, the model has made 60 percent difference in cropping pattern in such a way that the maximum cropping area belonged to fully irrigated Maize (3.5 ha) and by decreasing the amount of applied water, the model decreased the area under wheat cropping and increased the amount of deficit irrigation by 20.32 percent.

Irrigation canal lining is considered as one of the most effective strategies to optimal use of water resources. In spite of that a large irrigated areas are equipped for modern irrigation networks and also new irrigation networks are under construction, unfortunately, most of the networks suffer from various problems and result in low efficiency. Therefore evaluation of technical and operational situation of the constructed projects is inevitable in order to rehabilitation and giving remedial measures and approaches. In this study, technical, and operational problems of lined irrigation canals of Kerman Province were studied. To do this, several canals were chosen from different regions of Kerman. The study was carried out in two main parts: observation and measurements. Initially, the whole components of the network were observed and some interviews taken place with the network authorities. In this stage, the characteristics of the canals, water control and distribution structures and also related problems were recorded and analyzed. Subsequently, the water losses and conveyance efficiency of the studied lined canals were measured using input-output method. Based on the overall assessments and measured data, the problems involved with the Kerman canals were found to be numerous mainly; destruction of lining, sedimentation and finally low efficiency. Technical (designing and execution), geotechnical properties of the canal beds were the main reasons for the mentioned problems. Therefore, some suggestions were made to improve the efficiency of irrigation networks. Also it was found that the conveyance efficiency of Kerman lined irrigation canals vary from 57 to 81 percent.

A magnetic field is an inescapable environmental factor for plants in the soil. However, its impact on plant growth is not well understood. In order to assess the interaction of magnetic water and salinity on yield and components of Basil plant, an experiment was conducted under completely randomized factorial design with two treatments and three replications in greenhouse of Bu Ali Sina University. The treatments consisted of kind of water (magnetic and nonmagnetic water) and salinity treatment in three levels (3.57 μs/cm, 3.5 and 5.76 ms/cm salinity). The results showed that the maximum effect on increase the yield of components was by magnetic water. For salinity treatments, the maximum and minimum effects on yield components were related to the distilled water (3.57 μs/cm) and the water with 50 mM salinity (5.76 ms/cm), respectively. The interaction between the kind of water and salinity levels showed that 33% and 23% increase in total fresh and dry weight by magnetic distilled water treatment compared to non magnetic level, respectively.

The purpose of this research is the assessment and comparison of the gradeint and cultivation density impact on runoff generation at gun and furrow irrigation conditions. For this purpose, the experiments were carried out in a randomized complete block design with three replicate plots split by two times under field conditions. Danken test was used to compare the results. The results drawn from this research indicated that the type of irrigation system (I) at the level of 5 percent and effect of slope and cultivation density (S*D), dual impact of irrigation type and slope (S*I) and tripartite of irrigation type, slope and cultivation density significantly influnced on runoff volume and peak flow rate generated from gun and furrow irrigation systems at the level of 1 percet. However, dual impact of irrigation type and cultivation density (I*D) and the slope and cultivation density (S*D) did not have significant effect on runoff volume and peak flow rate. The results also showed that runoff volume and peak flow rate generated from furrow irrigation was more than system.

In the present study, field experiments were carried out at the research fields of the Agricultural Faculty of the University of Tabriz in a sandy-loam soil in order to determine the wetting pattern dimensions and soil moisture distributions in the vicinity of an emitter and also in a domain between the two adjacent emitters in a subsurface drip irrigation system. The obtained data from experiments were compared to the results from HYDRUS two-dimensional and three-dimensional simulations. Results showed that HYDRUS-3D was more efficient than HYDRUS-2D in simulating wetting pattern dimensions on the constructed soil profiles one just at the emitter location and the other between the two adjacent emitters with RMSE values of 2.54 and 3.96, respectively. Comparison of the obtained values from the two and three dimensional simulations showed that the two models had acceptable accuracy in simulating the soil water distributions on the profile at the emitter location. Also, by increasing the irrigation duration from 1 hour to 4 hours, the value of RMSE between soil moisture values obtained from the two and three dimensional models decreased from 0.068 to 0.025. Considering the good accuracy of the three dimensional model, the calibrated model was run for three different emitter installation depths and the suitable emitter installation depth for sweet corn production in the studied soil was recommended to be 30 cm based on the plant maximum water need, minimum deep percolation and evaporation losses and the plant rooting system.

To study the effect of different water salinity and water management on some of the agronomic traits of late summer melon with drip irrigation, an experiment with 7 treatments and 3 repeats was conducted in a randomized complete block design, in Torogh station, Mashhad. The irrigation treatments were: 1- fresh water from planting to harvest 2- water (3 ds/m) from planting to harvesting 3- water (6 ds/m) from planting to harvest 4- water (6 ds/m) from 20 days after plantation to harvest 5-water (6 ds/m) from 40 days after plantation to harvest 6-water (3 ds/m) from 20 days after plantation to harvest 7-water (6 ds/m) from 40 days after plantation to harvest. Result showed that, increased irrigation salinity had no significant effect of the number of seeds germination, but it caused that seeds germinated a little late. Irrigation treatments had a significant effect on the emergence of male flowers. With increasing salinity, reduced the number of male and female flowers but was not significantly different. The effect of water quality on dry weight of leaf, stem and stub was significant. The leaf area in two treatments that were irrigated with fresh and brackish water from planting to end, were more than other irrigation treatments at the end of growth. Increasing salinity lead to increase the chlorophyll density. The yield average of fresh water was 17.5% and 26% higher than brackish and salinity water respectively, that difference between the yield of fresh water and two other waters were significant (about 5%). But had not significantly different between the yield of brackish and salinity water.

Study of the hydraulic and technical characteristics of emitters is one of the most important issues in trickle irrigation research. The researcher carried out her work with nine types of pressure compensating emitter with codes of A, B, C, D, E, F, G, M and N based on a trickle irrigation physical model. All experiments are based on ISO 9261 standard and IRISI 6775 standard of the Institute of Standards & Industrial Research of Iran. The obtained results are as follows: 1) According to the Manufacturing coefficient of variation and difference between the actual and nominal flow rates, models B and F were rated as good, models A, C, E and G as medium, and models D, M and N were ranked as unacceptable. 2) According to the EU, models B, C, F and G were ranked as excellent, models A, D and E as good and models M and N were rated as weak. 3) According to the UC, all models except M and N were more than 70% and their flow rate variation have normal distribution 3) Considering all manufacturing quality standards and emission uniformity of emitters, models B, C and F were nominated as the best emitters.

The aim of this study was to estimate actual evapotranspiration at regional – annual scale using semidistributed Soil, Water Assessment Tools (SWAT) model in the Neishaboor watershed. For this reason, SWAT calibration and validation was done based on river discharge data from 5 gauging stations, rainfed and irrigated wheat yield data for the period Oct. 2000 to Sep. 2007 and Oct. 2007 to Sep. 2010, respectively. Because of the direct relationship between crop yield and evapotranspiration, calibration of watershed models using crop yield along with river discharge gives more confidence on the partitioning of water between soil storage, actual evapotranspiration, aquifer recharge. The results showed that SWAT provided satisfactory predictions on hydrologic budget and crop yield. Specifically, calibration (R2 = 0.82, NS=0.79) and validation (R2 = 0.71, NS=0.71) periods were quite suitable for the outlet of watershed. It also was able to predict crop yield satisfactorily for irrigated wheat in which R-factor and RMSE values were 0.97 and 0.08 ton ha-1, respectively. The multi-objective calibrated model was then used to estimate and analyze the actual evapotranspiration. Mean ten-year actual evapotranspiration and precipitation was estimated 230 and 270 mm, respectively. The ten-year actual evapotranspiration to precipitation ratio at mountainous part of watershed was 99%, 80% and 77 for 2000-2001 as a dry year, 2001-2002 as a normal year and 2004-2005 as a wet year, respectively. Groundwater is an important source of water supply in the Neishaboor plain. Therefore, estimation of this ratio is not as simple as mountainous part of watershed due to uncertainties in the crop pattern data and their water requirements. It is obvious that this ratio could be more than one in some years especially dry years.

Gabions are one of simple methods of control erosion and flood and reducing of flood damages. Field survey show behind most of the gabions is filled by coarse sediment and debris. Therefore, in this study the role of these dams for maintenance of sediment was investigated. To conduct this 16 gabions on Zidasth, Taleghan were selected. Sampling was conducted from 0-50cm depth on the deposition sediment in the gabions. Correlation analysis by SPSS software between area and volume dam was conducted. For this were estimated of mead diameter, D50, D95, Sorting percentage of provincial flower and the percentage of sand and gravel. The analysis sediment gradation curve was show much of the sediments deposited in the dams are coarse and so, they are located in the range sand to gravel. The results were show only correlation of the volume and mud was significant. Others factors has not significantly correlation with dams area and volume. So, the location of dams should be selected so that cause coarse sediments sedimentation is in the natural stream. In addition, dam reservoir volume is large. This cause a calm flow and fine sediments deposition.