Iranian Journal of Irrigation and Drainage
Year:2013 | Volume:6 | Issue:4|Papers Count:10

Hydraulic performance of emitters plays a major role in the trickle (drip) irrigation system uniformity. But, manufacturing proper emitters is highly expensive and time consuming. On the other hand, the study of flow behavior of the water passing through emitters' channels is difficult because of their small size and complexity. Therefore, it seems that Computational Fluid Dynamics (CFD) can significantly contribute to the study of flow hydraulic characteristics in emitter channels. In the present study, the three emitter codes A, B and C were selected and their channels size determined using the Scanning Electronic Microscope (SEM) for taking the pictures of channels. The flow in emitters channels was simulated with the two software FLOW3D and FLUENT. In this study laminar and turbulence models were applied for the simulation of flow in emitters’ channels, the discharge for each emitter was calculated. Verification of the CFD simulation results with those obtained in laboratory showed that Relative error value (Er) for laminar model of FLUENT, turbulent model of FLUENT, laminar model of FLOW3D, turbulent model of FLOW3D was 4.0, 4.4, 5.3, 12.0 per cent respectively. Laminar model estimated emitters discharge less than turbulent model. Also, it was shown that in both models FLOW3D and FLUENT the error calculated for turbulent model is greater than laminar model and that FLUENT software is more efficient than FLOW3D in the simulation of flow within emitters’ channels. But, generally, it can be said that the two software tools can simulate flow in emitters' channels with a good accuracy.

Due to reduction of water resources and increasing demand for water saving, optimum use of available water is necessary. One of the irrigation methods with low water consumption and good efficiency is drip irrigation. The objective of this study is to investigate the technical drip irrigation systems (micro irrigation) in Fars Province, in 124 gardens and farms which have different climate conditions. The values of CU, DU, EU, AELQ, PELQ and CV in Fars province were in range of 61-97%, 50-95%, 43-93%, 34-93%, 30-84% and 5-52%, respectively, with average of 86%, 80%, 75%, 72%, 65% and 18%, respectively. The pressure in emitters were between 0.3-22.9 m with mean of 8 m. In about 64% of systems the pressure was less than 10 m. The discharge of drippers was between 0.6-55.1 lit/hr with mean of 5 lit/hr. But in 74.1% of systems the discharge was less than 3 lit/hr. The mean of wetted area was between 8.9-47.3% with average of 27.8%.

A proper understanding of factors affecting evaporation and wind drift losses (Ls) in sprinkler irrigation is important for developing water management strategies. In semi-arid areas such south Iran the portion of water that may be lost due to wind velocity and evaporation would be significant. The objectives of this study include characterize Ls for two type sprinklers ADF 25o with three nozzles and Nelson F80APV with one nozzle under different conditions for solid set system and propose predictive equations by multiple regression for Ls in semiarid areas. In solid set system often one sprinkler worked on each line and they don’t have enveloped each other at the same time this can be a reason for difference of Ls in this method than others. The experiments conducted in Shahid Chamran university of Ahwaz. Four operating pressures in range of manufacture recommended for each sprinkler had applied. The factors investigate were include operating pressure, wind velocity, environment temperature, relative humidity and vapor pressure deficit. In experiments condition Ls ranged from 1.4 to 12.8 percent of applied water. The result showed that, wind velocity and vapor pressure deficit were the most significant factors affecting the Ls. The operation pressures used had the least effect on Ls.

In this research the impact of climate change on crop yield, and water requirement of the main crops (wheat, barley, corn and alfalfa) has been evaluated in Hashtgerd plain with respect to the uncertainty of Atmospheric Ocean General Circulation Models (AOGCMs). To produce monthly temperature and precipitation scenarios,, temperature and precipitation were extractedfrom nine AOGCMs under the A2 emission scenario (CCSM3, CGCM3, CSIRO Mk3, GFDL CM2.1, GISS ER, HadCM3, ECHAM5, MIROC-med, PCM) in the period 2010-2100 AD. Using Monte Carlo and weighting methods, 2000 time series of temperature and precipitation scenarios were produced for each cell (5o×5o) in the whole plain. Afterwards, these scenarios were downscaled by change factor method for the area. Finally, using AEZ/GIS and Hargreeves-samani approach, the potential yield, and the crop evapotranspiration was assessed in the region in the period 2010-2100.The agricultural water productivity was also studied in this plain., The results were depicted in range of variation in each period. On the whole, variation of the results revealed the enhancement of water requirement and reduction of the yield in the future periods in this area. Water requirement increase in wheat 15-28, maize 9-14, alfalfa 18/6-34/7 and barely 10-21 millimeter in each periods to 2100 year. On the other hand the range of decrease for wheat, barely, alfalfa and maize will be 50-138, 44-136, 327-508 and 17-24 kilogram per hectare respectively. The results also showed decrease in variation of water productivity in all crops in future periods. Furthermore, in this regard, alfalfa has had the biggest (104-156 gram per Cubic Meter) and wheat the smallest (55-93) reduction in productivity.

One of the main problems is the influence of surface water irrigation and non-uniform soil moisture profile below the soil surface which reduces the efficiency In this simulation, it was to influence both the water and irrigation.For this purpose, the surface flow equations and the equation of Nantes and the water in the porous medium equation to be done Rychadz Then, using the influence of surface irrigation was sirmod Simulation the flow of irrigation water and Results showed the model to solve the equation hydrus Rychadz error is less The accuracy of numerical simulations based on Richards equation for solving the given number of observations and comparison with moisture in the soil profiles developed in hydrus wet volume was evaluated RMSE hydrus results compared with observational values are (RMSE 0.11) and R2=./92 in different depth Was achieved. The model also estimates hydrus appropriate volume of water to furrows adjacent furrows in the soil moisture distribution can be well simulated.

In our country, the main portion of water resources is allocated to agriculture uses. Therefore for each river basin water resources planning, it is essential to know value of agriculture parameters. The goal of this research is estimation of best value of agriculture return flow fraction and return flow contribution to surface and groundwater. This is accomplished by automatic calibration of water resource planning model, MODSIM, and integration this model with Particle Swarm Optimization algorithm. Objective function of calibration includes surface discharge and also groundwater level terms. The return flow fraction of agriculture demand for Gawshan Basin in the West portion of Iran, as a case study, was obtained 33.7%. Also results indicate that agriculture return flow fraction contribute to surface groundwater inflow is equal 14.5 and 85.5 percent, respectively .Calibration of water resources planning models is a good approach to estimate return flow fractions at river basin wide.

In order to investigate thewater productivity of rice in Rasht, a study was carried out in a RCBD during 2005 and 2007 years, with 3 replications in Rice Research Institute of Iran, Rasht. Irrigation management (3 regimes) was the main factor and N application (4 levels) was the other factor. In this study, simulation modeling was used to quantify water productivity, and water balance components of alternate for water–nitrogen interactions in rice. Results showed, the significant (28–56%) share of evaporation into evapotranspiration, using the actual yield (measured) and simulated water balance (ORYZA2000), the calculated average WPET was significantly lower than the average WPT: 37%. The average WPI, WPET, WPT and WPETQ were 1.01, 0.89, 1.41 and 0.65 kgm-3. Also Results showed that, Irrigation with 8 days interval and 60 kg N ha-1, was the optimum combination.

Groundwater is a free water resource for agriculture. In this research two-year experiments from year 2009 to 2011 was conducted to find the percent of groundwater contribution in the presence of groundwater level with 80cm depth and two supplementary irrigation procedure during flowering and both flowering and seedling conditions on three wheat cultivar namely W33g, Cross Alborz and Bahar in three replicate randomized complete block factorial experiments. Experiments performed at Razi university lysimeteric research station No1. Results showed a significant difference (P<0.05) between two supplementary irrigation treatment. Also the highest groundwater contribution was found equal to 71.37% for treatment with one supplementary irrigation during seedling period (for W33g cultivar) and the lowest groundwater contribution was found equal to 63.50% for treatments with two supplementary irrigation (for Bahar cultivar) in the first year. The highest and lowest groundwater contribution equal to 76.86% (for Cross Alborz cultivar with seedling supplementary irrigation treatment) and 66.40% (for W33g cultivar with two supplementary irrigation treatment) was found in the second year respectively. Moreover, from point view of yield production, the highest value was obtained for W33g cultivar during both years of the study.

About 70% of irrigation water is taken from groundwater resources in Fars province, Iran. Water use management could have a significant role in an efficient water use and increase the water productivity. There are some instruments for irrigation management, which we have few information about their performance in Iran. In the present study, the performance of some irrigation management tools, in two maize farms is evaluated. The farm located on Sheshdeh-Gharebolagh plain in Fars province, and the farm was irrigated using drip irrigation system. Irrigation water was scheduled using tensiometer, infrared thermometer, gypsum block, soil moisture meter and the national water requirement document. The irrigation water applied by the farmer was also measured. Results showed that the irrigation scheduling tools can reduce the farmer applied irrigation water about 35%. The yield was not significantly affected by the irrigation scheduling treatments. The water use efficiency increased about 47% comparing with the control farmer management. The best irrigation management tool was gypsum block.

In this paper, application of in-line storage strategy to improve operational activity of main irrigation canal is assessed. The mentioned strategy is implemented using Model Predictive Control (MPC) method. The designed MPC applies a prediction of water perturbation due to water off taking along the main canal, in an appropriate 7 hours horizon time in future, and taking physical limitations of the system into account. A normal canal operation and an unconventional operational scenario with a 6 hours limitation on the head-gate adjustment, based on night storage conditions, is considered for simulation. The proposed strategy is tested on the Dez main canal with 44 Km length which consists of 13 canal reaches. Different Target bands are created between the predefined maximum and minimum water level for the canal reaches and the MPC controller is allowed to control water levels in this range. The results show that the best inflow values are calculated by the designed MPC controller, so that during the first 3 hours canal reaches are forced to store water and in the next 3 hours the stored water is consumed. Water level profiles imply that water level changes for all of the canal reaches are within the target band, so water off-taking activities are not thrown into any disorder. Hydraulic performance indicators show that just in one canal reach and for a short time, water level exceed the target band with the MAE value of 1.4 %, and for the other canal reaches water levels never violate the allowed maximum and minimum target.