Iranian Journal of Irrigation and Drainage
Year:2009 | Volume:3 | Issue:1|Papers Count:13

Physical or chemical clogging can obstruct a drain envelope and disable agricultural drainage systems. Chemical clogging can be formed by various substances. First step in recognizing clogging phenomena is to find out about precipitation materials. Calcium carbonate is a substance with low solubility that can be precipitated rapidly and makes the hard pan layer and obstruct the drain envelope. This study investigates the potential of calcium carbonate precipitation existing in agricultural drainage water in Khuzesta Oprovince. In this study three indicators such as Langelier, Ryznar and Stiff&Davis index were used to find out the potential of calcium carbonate precipitation in agricultural drainage Water. Results showed that all of agricultural drainage systems in this study area have potential of calcium carbonate precipitation but the severity of precipitation potential is varied. In the meantime results also showed that the Stiff&Davis and Ryznar indexes in comparison with Langelier index have better estimation for determination of potential calcium carbonate recipitatioll.

This study identifies the impacts of inigation networks on irrigation management improvement and farmer's socio economic conditions in Moqan, Tajan and Varamin schemes WUAs in Iran. The study is an applied research and research method is descriptive-correlative. The stUdystatistical universe was consisted of farmers who were member of water user aSsociations.A sample of 262 farmers were selected using "random sampling" method. Data collected by a questionnaire which its validity (Face and content validity) was obtained by a panel of experts and university professors and Jihad agriculture Ministry experts. Reliability measuredby Cronbach's Alpha coefficient and a=.721 showed the reliability of the questionnaire. SPSS/win 11.5 softwate was used for data analyzing, and factor analysis and correlation coefficient method were employed in this research. The results showed that between farm plots, number of farmers in WUAs, low problems', WUAs success, farmer participations and Water users' association (WUAs) affects in farmer's socio -economic improvement were significant relation. Also the result of factor analysis showed that the variables set in 4 factors namely as, farmers knowledge and income improvement, region economical improvement, agriculture diversity, and low penetrate of large farmers.

A new approach based on Artificial Neural Networks (ANNs) is preSented to simulate the distortion of single sprinklerwater distributionpatterninfluencedby windundercenterpivot irrigationsystems. Field experiments were conducted at the Research Center of Agricultural Faculty, University of Tabriz-Iran. The distribution pattern of Nelson R3000 RotatorÒ sprinkler was tested at various wind velocities and directions. Experimental dataset were divided into three subsets named as training, validation, and testing datasel Affecting parameters were defined and various networks with different structures were trained and validated. A Multi Layer Perceptron (MLP) neural network with back propagation training algorithm having two hidden layers, 20 neurons in the first hidden layer, and 6 neurons in the second hidden layer and tangent-sigmoid transfer furiction was selected as the optimal network and produced R2=0.929 and RMSE=6.69 for test dataset. Usingthe structure of the optimal network, a model named ISSP (Intelligent Simulator of Sprinkler Pattern) was developed as a MATLABÒ m-file. Entering wind velocity and direction as the inputs, this model could simulate the distribution pattern of R3000 Rotatore spririkler arid have ability to display graphical and ExcelÒ file of results. Simulated distribution patterns of this model for three different wind speeds were compared with obserired distribution patterns. Obtained resuits showed that there is no meaningful difference between. R2 values for these three conditions and these values are in a very appropriate range (R2>0.935).

Nitrate (NO3-N) and ammonium (NH4-N) leaching from agricultural soils can represent a substantial loss of fertilizer nitrogen (N), but a large variation in losses has been reported. The objectives of this sfudy were to assess the accumulation and movement of nitrate and ammonium in the soil profile over studying period under deficit irrigation conditions. We report N concentration and leaching losses.under three N fertilizer and three irrigations treatments in Khuzestan. Irrigation treatments consisted offutl irrigation (II) and others were 80 (12) and 75 (13) percent of II treatment. Urea application consist of 150 (N1), 250 (N2) and 350 (N3) kglha. Leachate from the farm was extracted from a depth of 1.2 m and soil samples were collected from field plots in 0.3 m depth increments to 1.2 m on a periodic basis. NO3-N values increased with rise of fertilizer consuming and decreasing of water application. It depended to NH4-N transformation and irrigation regimes. In all treatments, NH4-N decreased from the surface to 120 em depth. Maximum concentration of NO3-N and NH.-N accrued in I3N3 and I3N2 treatments respectively. Temporal variability in nitrogen concentrations in the soil depths were mainly the result of different irrigation and fertilizer regimes. Our results indicated that the irrigation regimes in this study lead to relatively N leaching losses, appropriate fertilizer application with enough irrigation can substantially reduce these losses.

Substituting manhole structures in agricultural drainage and urban sewer networks where it is applicable. with simpler junctions at the connection of the lateral and collector would considerably improye the project economy. Such pipe fittings have been used in many countries and recently were manufactured and used in drainage and sewer networks in Iran. However the hydraulic characteristics of these fittings and their influences on the discharge capacity of the network. Which has a decisiye rule in the design process? Were yet to be known. In this research by construction a specific prototype-scale experimental setup the hydraulic characteristics.of the thread-type and hand-made junctions were investigated and determined. Data were compiled for wide-ranging of longitudinal slopes and discharge ratios and the local head loss coefficients were determined aIld presented in dimensional and non-dimension plots. The possibility of proposing an average value for the coefficients for the ease of practical applications and their impacts on the predicted values were also investigated. The results indicated that the application of average coefficient values predicted the water surface profile reasonably. Especially for higher discharge values which are usually considered in the design process. The application of the results of this research in conveyance capacity determination models could reduce the uncertainties of the design process and assist in choosing reasonable safety factors.

Production of a suitable emitter need time and is expensive. On the other hand, because of stnall size and complex structure of labyrinth-channel used in most of drip emitters, it is not possible to observe the flow behavior of water passing through the channel. In this study, the flow in labyrinth channels was simUlatedby using the method of computational fluid dynamics (CFD) to calculate the distributions of pressure and velocity of the flow. And relationship between pressure and rate of discharge under six levels of pressure were studied. For this purpose, three samples of one type emitter were selected. The emitters were destroyed and sizeSof those channels were calculated by photography with Scanning Electronic Microscope (SEM). To calculate the relationship between pressure and rate of discharge as well as simulation of flow in emitters' channels using Computational Fluid Dynamics (CFD), laminar flow model and turbulence model was applied. The results were compared with the pressure and flow rate from laboratory test. Results of simulated data showed a good agreement with the experimental data and also difference between laminar and turbulence models were not significant.

Water resource limitation, irrigation scheduling, undesirable and non economical water use are the most important limiting factors of agricultural development and production in Iran. For desirable and optimum use of water different themes are under discussion; irrigation scheduling, improvement in on farm water management, improve in water productivity and water economy profitability. This study was conducted to determine propose irrigation schedulitig (time and depth) for wheat and barley under different water quality and quantity at field scale to improve water productivity in Abshar network in Esfahan. Optimal irrigation depth, schedule and yield water- salinity function for wheat and barley was defined using combined fixed and variable cost, yield fees, on farm and simulated data for different water quality and quantity. Accordingly, crop yield and water productivity of wheat and barley simulated and compared to the on farm condition. Result indicated that wheat and barley yield increased 15 percent by improve in irrigation scheduling. In the other hand with improve agronomic management and decrease 20 percent of irrigation depth, crop yield variation was very low. As a consequence, optimal irrigation depth increased when irrigation water salinity increased, but differences in optimal irrigation depth decreased under limitation of water and land. Increase in applied irrigation water uritil optimal depth caused economic water productivity increased, but water applied more than optmal level has no significant effect on water productivity and economic water productivity. According to the results, proper irrigation scheduling to gether with improved agronomic management, increased crop yield and water productivity about 16 and 45 percent, respectively.

PRD (partial drying of the root zone) is a new deficit irrigation technique in which one side of the root system is irrigated, while the other side is dry. In this research, effect of PRD on nutrient content, dry matter, harvest index, and root distribution in canola (Brassica napus L., var. Zarfam) under deficit irrigation and relatively high irrigation water salinity was studied in Agriculture and Natural Resources Research Center of Yazd in 2006. The PRD experiment had five treatments (T1: irrigation of both sides ofthe plants, T2: alternate irrigation on both sides of the plants, T3: irrigation only on the right side, T4: irrigation of right side of the plants without having a vertical division barrier in the boxes, and T5: alternate irrigation of the plants without having a vertical division barrier in the boxes). In T1 to T3 treatments, the boxes were halved by a thin vertical division barrier so that water cannot move ITomone side to the other. Electrical conductivity of irrigation water was 6.56 dS/m. The results showed that water use efficiency of T1 was 0.376 and that of T2 treatment was 0.679 kg/m3 and the difference was significant at 1% probability level. Halving the amount of irrigation water in T2, with respect to T2 caused the content of P, K, Mg, Na, CI, Cu, Zn and Fe to increase and ofMn and Cato decrease in canola plants. T2 treatment had 0.8% more dry matter and 0.09% less harvest index as compared to T1. These differences were not significant statistically. The root distribution systems showed that the plants which were irrigated on both sides had more uniform deep roots and the plants which were irrigated only from one side had roots on that side only. The root distribution was effective on nutrient uptake.

Moisture front of trickle irrigation system is oUtstanding and important properties to be considered for designing of the system. The dimension scale and direction of moisture front can increases the water consumption and irrigation system efficiency. Using Super Absorption Polymer (SAP) could be consider to increase water productivity and irrigation efficiency in the soil. The objective of this research is study the effects of SAP on soil properties and the scale of moisture front. An experimental field complete block design was conducted in four level of SAP in three replications. The difference betWeentreatments was the amount of SAP by 0, 0.1, 0.2, 0.3 percent of soil wight and constant flow volume in three irrigation of time schedule. The result showed that application of SAP improved some of the physical properties of soil. For example the hydraulic conductivity and saturated volume of water and specific gravity. The results also showed that the depth and the moisture wide of wetted soil moisture front in first experiment was different compare with other irrigation period.The wide of wetted soil of moisture front in first irrigation period in wettness treatment is greater than other treatment and this is not true in next irrigation periods but it had smaller front ,moisture. The standard variation analysis indicated that depth of wetted soil and wide of moisture front has significant difference in five percent of probability level. Result of comparison among all applied treatments by using 0.3 percent SAP in soil showed significant difference in order to increase the depth and wide of wetted front of soil moisture.

Optimum and effective operation of classical hydraulic jump in irrigation and drainage networks needs appropriate tail water in downstream of the stilling basins. FOi:any reason whether downstream tail water of hydraulic structure is less tail water than classical jump's one, establishing 01 expansion in flow section is an appropriate solution for decreasing necessary tail water depth, which can reduce the cost of stilling basin construction too. In this research, hydraulic jump characteristics were experimentally investigated in rectangular section with abrupt and gradual expansion. Abrupt and gradual expansions (30°, 45°, 60°, 75°,90°) for three expansion ratios (downstream channel width to upstream) of 1.5, 2.5, 5 were installed in the rectangular channel (in a flume with 6x1x0.7 m long, width and height respectively). For different Froud numbers of flow, hydraulic jump characteristics were measured in these sections and the results were analyzed. Asymmetric vortices (clockwise and non-clockwise) associated with jump, established in the left and right hand of the jump, as flow passed through the expanded section in which their size and rotation velocity were completely different. Hydraulic jump characteristics including secondary depth, length and depth of jump, radius and rolling velocity of the vortices were investigated. The results of this research showed that decreasing divergence angle in different expansion ratios, decreased undesirable characteristics of spatial and transitional jumps in which, finally their conditions could be better than the characteristics of classical jump. However, for any expansion ratio, modifying divergence angle nom 90° to 30°, considerably affected the secondary depth (related to classical jump), but sequent depth ratio does not significantly modify. As expansion ratio and divergence angle decrease, expanded jump has shorter length related to classical jump. Hydraulic jumps in expanded section always have more efficiency than classical jump and with change of divergence angle for constant expansion ratio; this efficiency does not modify significantly. Finally, the optimum conditions of expanded jump could occur with expansion ratio of 2 and divergence angle of 60°.

Optimal water and nitrogen use is an important approach in arid and semi-arid regions. Crop simulation models may be used for studying cropping systems and optimizing these variables. The preSent study was carried out with the main objective of validation and performance evaluation of the detailed CropSyst model under varying N levels and water regimes. Its potential as N and water managementtool was evaluated based on a field experiment in an arid irrigated ecosystem. The field experiment was carried out in a randomized complete block design with four replicates. There were four levels of applied water and three levels of N application as treatfu.entsin the proposed plots. The predicted grain yields had a good agreement compare to the observed data with RMSE of 0.41, 0.33, and 0.34 t ha-1 for the three growing seasons. The prediction of biomass was also satisfactory with significant R2 (>0.8) and Wilmot's index (0.9) values. The comparison of observed and predicted water productivity values showed that the estimations have more difference in the deficit irrigation regimes. The results indicated that the maximum water productivity value is related to the full irrigation and N application 120% of crop nitrogen demand and minimum water productivity value was occurred in applied water with a 120% of crop water demand and N application 60% of crop nitrogen demand. Consequentry, when limited supplemental irrigation is combined with N fertilizer appropriate management. Wheat water productivity can be substantially and consistently increased. The findings demonstrated that CropSyst model is an appropriate tool in predicting growth and yield of wheat under differentN and irrigation application situations in this study and may thus be applied as a comprehensive and practical decision-making tool with the aim of improving wheat water productivity.

The rectangular settling basin is one of the common hydraulic structures, especially in irrigation systems, which is used for the separation of suspended sediments from sediment laden flow. In this study the effect of a submerged flat plate normal to the flow direction, on the trap efficiency of a settling basin Wasexperimentally investigated. The results indicate that in 3D conditions in which the incoming jet travels a considerable distance from the inlet and causes large variations of transverse velocity in the basin, installing the baffie in a relative submergence of 20% and a relative distance of 6% can increase the trap efficiency of the settling basin by up to 12%. This may be attributed to the role of the baffie in decaying the kinetic energy of the impingingjet and spreading the sediment particles in the width of the settling basin.