Journal of Irrigation Sciences and Engineering
Year:2012 | Volume:35 | Issue:2|Papers Count:12

Emitter is the key component in drip irrigation system. Therefore, hydraulic performance of emitters has an important impact on the performance and uniformity of trickle irrigation. On the other hand, process production of emitter is time-consuming and expensive. Because of small size and complex structure of labyrinth-channel used in most drip emitters, it is not possible to observe the flow behavior of water passing through the channel. In this study three types emitter (A, B and C) were selected and structural parameters of emitter channel was determined by taking photos using Scanning Electronic Microscope (SEM). Flow behavior of water in channel simulated by two Computational Fluid Dynamics (CFD) software FLUENT and FLOW3D. Then relationship between pressure and rate of emitters discharge was calculated. Verification of the results obtained from the CFD simulation was conducted in laboratory. Average of prediction error percentage (Er) was 5.5 and 3.6 percentage for FLOW3D and FLUENT software respectively. Therefore results indicate that the FLOW3D and FLUENT softwares are a powerful technique to simulate flow behavior of the water passing through channels emitters, as well as to optimize the design of the labyrinth channel.

Due to the high ability of Iran for producing Activated Carbon and the Fact that (1) it is not produced in the power from with particle size of lower that 100 nm in the country, (2) to production in the power from is not suitable, (3) high necessity for it and (4) its high inports to the country, the production of activated carbon with good adsorption properties are very important. For producing activated carbon, different raw mterials need to be used. In the investigation study, cheap and available phragmites australis were used. By physical activation, activated carbon was produced and then the effect of activated carbon on reducing dissolved solid was investigated. Carbon and activated carbon samples of phragmites by using pilot-scale furnace in the laboratory were produced. Additionally, the effect of each process variables such as adsorbent material (carbon and activated carbon), the mass of adsorbent and concentration of dissolve solids on the absorption capacity, production efficiency and absorption properties of carbon and activated carbon were investigated. Then the optimum production conditions were determined. The results showed that phragmites australis was cheapmaterial with suitable physical properties for activated carbon producing, and that the activated carbon has higher adsorption capacity than carbon. For there moval of dissolved from water.

The standardized precipitation index (SPI) is used vastly for drought monitoring. Among the many of drought indices, the using of SPI for drought events in various time scales is more important. The SPI calculation is based on fitting a probability distribution that describes an observed series of precipitation. There are many models for obtaining probability distribution and parameter estimation, but choosing an appropriate approach is important. This paper employs the four-parameter kappa distribution and techniques of parameters estimation for calculation of SPI. The parameters of kappa distribution are estimated by the genetic algorithm and method of maximum likelihood, and finally the results indicate that the genetic algorithm is more satisfactory for parameters estimation and SPI prediction.

A main source of sediment transport in damreservoir and lakes are density currents. A main parameters in density currents, is sediment entrainment in the body. In this study the effective parameters of sediment entrainment was studied. Experiments were conducted in hydraulic modeling laboratory of hydraulic engineering department, Shahid Chamran University of Ahwaz. The measuring section includes a flume with adjustable slope, 9.25 mlong 0.5 m width and 0.75 m depth. Results show that, by increasing shear velocity and concentration of inflow, sediment entrainment coefficient of body will increase. Normally, sediment concentration in the body of the current will decrease due to sedimentation but in the currents with sediment concentration less than transport capacity, sedimentation are not occurred. Finally, two equations are proposed for estimating sediment entrainment coefficient of the body of turbidity currents.

Using of a hedging rule during drought periods is a usual approach in water resource management. In this method, although may be possible to satisfy all of demands, occasionally, portions of demands are met. This policy saves water with imposing a little deficit in the current period instead of a severe water shortage in future, which is effective for social and economical aspects. One of the key points in this regard, is to calculate optimal rationing factors for different purposes and optimum trigger volume for each reservoir to start hedging rule. For this purpose, in the present study, a coupled simple geneticalgorithm to the simulation model (ARSP) including flow network penalty structure and linear programming model is used. The capabilities of the model are investigated in the Zohreh water resource system as a case study located in west southern of Iran. The results show that the combination model improves intensity of water shortages in comparison with the situation of without hedging rule. Moreover, the model provides the possibility of considering more details for the water resource systems.

In this investigation groundwater modeling is attempted monitoring water table fluctuations of Jiroft basin using PMWIN computer model. Parameters like hydraulic conductivity, specific yield and groundwater abstraction and recharge were estimated by matching of the data from 41 observation wells for the period 1381-1386 to those predicted by the model using automatic calibration procedure with PEST. Verification of the model for a 6 month period in 1387 showed that the predicted water levels had a good match with the observed water levels with a root mean square error of 0.865. The verified model was used for the prediction of groundwater table behavior for the next 4 years.

Improvement in numerical techniques and computers now make it possible to solve rather complicated porous media flow problems. In this paper, Richards's equation is solved by control volume method. A computer model was developed for calculating water content and pressure head in unsaturated soils. For determination of soils hydraulic parameters, this model is linked with RETC code. Results of model are compared with experimental data and show that control volume method presents a correct solution of the Richards equation.

In the last two decades, researchers have been more interested in river flow forecasting by means of nonlinear models, Genetic Programming, Time-Series, Wavelet Analysis, etc. included. Wavelet transform by decomposition of signals into time and frequency, same as Fourier analysis has presented a new method for signal processing. Meyer discrete wavelet was used for prediction of average monthly Lighvan-Chai river flow, using 90% of data for testing. The results revealed that 10 levels was the most appropriate number of levels, the best monthly forecasting horizon was 12 months and the correlation coefficient between observed and anticipated ones was 0.92 at Lighvan station and 0.91 at Hervi station. Moreover, in time series, ARIMA ((1, 0, 1), (1, 1, 1))12 had the best results with correlation coefficient 0.87 at Lighvan station and 0.93 at Hervi station. According to data, time series has analyzed peak points better than the other one. Overall, with attention to correlation coefficients and attention to that complex series change into simple series with wavelet transform that series had analyzed easier, so wavelet transform is more proper than time series.

Determine of design maximum intensity of precipitation is necessary in hydrologic design of hydraulic structures. It's amount often obtained from rainfall Intensity-Duration-Frequency (IDF) curves. In this method, there is required maximum annual intensity of precipitation in different duration that this data for some of the durations aren't usually available. Also, this method requires large number of parameters and these parameters depend on return period. In present research the combined fractal theory and Generalized Extreme Value (GEV) distribution were used to calculate the design maximum intensity of precipitation from annual 24-hours maximum precipitation series. The results at Tale-Zang site which located in North Khuzestan province within the latitude and longitude of 48 46 north and 32 49 east show that precipitation fallows the mono-fractal process between 1 to 8 days and estimates design storm using fractal theory are more accurate compared whit the observed rainfall.

Limitation of water resources has made important the application of deficit irrigation subject as a efficient property to increase water productivity. Deficit irrigation subject needs many researches. Doing these research can improve deficit irrigation management in the Limitation of water resources. The purpose of this study is evaluation of different deficit irrigation scenarios and determine optimal hydromodoul and area of cropping pattern in the deficit irrigation conditions to increase water productivity. A plant growth model was used in order to examine yield and stress in result of applying three different deficit irrigation (10%, 20% and 30%) in fava bean, bean, wheat, potato and sunflower crops. Crop water requirement, Net Benefit Per Drop index (NBPD) and cropping pattern hydromodoul were calculated and on the bases of three criteria, different deficit irrigation scenarios were evaluated. The results show, as the optimal cropping pattern is related to water consuming, optimal production and profit, so the selection of optimal deficit irrigation levels on the bases of maximum water productivity index is suitable. Amonge of all the possible cropping pattern combinations, a cropping pattern that it consists of 10% of deficit irrigation for fava bean and bean, 20% for sunflower and potato and 30% for wheat has maximum of NBPD (with 15750 Rials per cubic meters) For this cropping pattern, the optimal area in comparison with full irrigation has increased 11% and average optimal hydromodul in comparison with average hydromodul of full irrigation shows about 18% reduction.