Journal of Irrigation and Water Engineering
Year:2013 | Volume:3 | Issue:11|Papers Count:10

Alternate furrow irrigation is one of deficit irrigation methods that is used to increase water use efficiency and can be applied to mitigate water shortage in agricultural lands. The objective of this research is to compare hydraulics of water flow in the alternate and traditional furrow irrigation regimes. Field experiments were conducted for three furrow irrigation regimes, i.e. alternate (AFI), fixed (FFI) and conventional furrow irrigation (CFI) at Experimental Station of University College of Agriculture and Natural Resources, University of Tehran, Karaj in 2010. The comparisons were done based on three irrigation events. The results indicated that advance times did not differ between AFI, FFI and CFI. However recession times for AFI and FFI were smaller than CFI. Cumulative infiltration in AFI and FFI was higher resulted in lower runoff losses compared to CFI. Irrigation application efficiency in three irrigation events for CFI, FFI and AFI were ranged 33.3-56.2, 58.8-71.8 and 60.7-77.0%, respectively. Infiltration in the every-other furrows did not change in following irrigation events because of more lateral water movement, but infiltration was decreased in the traditional furrows. CFI had more soil water than AFI and FFI. Soil water content in AFI was somewhat more than it in FFI. This study also showed that with simple modification in the traditional furrow irrigation, irrigation operation cost and water consumption would be decreased. Furthermore, the performance of irrigation system can be considerably improved.

Soil moisture as an important factor in agricultural management which is measured or estimated using direct and indirect methods. Time domain reflectometry (TDR) method is One of the newest and fastest ways to measure the soil dielectric constant, indirectly which is based on the measurement of soil dielectric constant regarding the velocity of the electromagnetic waves propagation. In this paper, several experimental relations between dielectric constants and volumetric water content have been presented, but all soil properties is not considered in these methods. The main purpose of this research is the investigation of the effect of soil texture on the accuracy of volumetric water content measurement by use of TDR system. The experiments have been carried out on 5 types of texture (sandy, sandy loam, loam, sandy clay loam and clay loam) in three repetitions under quite random conditions. In addition to assessment of soil moisture using TDR, soil volumetric water content has been measured in direct (weight) method. Also, Estimated Values of soil moisture by the TDR system were compared with topp et al (1980) and mixed models. The results showed that the volumetric water content values obtained from TDR system decreased with The heavier soil texture, As the percent relative error (RE) in textures sandy, sandy loam, loam, sandy clay loam and clay loam have been Respectively equal to 4.07, 8.9, 8.03, 9.13 and 11.4. comparision of estimated moisture using models showed that in all textures, topp et al (1980) models had the highest Correlation coefficient and also The accuracy of topp models is more of mixed models. Finally, Relations have been calibrated with a high correlation (R2) between weight and TDR moisture measurements were presented.

In order to evaluation the effects of irrigation levels on yield, yield components and water productivity of soybean T.215 cultivar, an experiment was conducted based on Randomized Complete Block Design with three replications at Agricultural Research Farm, Faculty of Agriculture, University of Guilan in 2009. The treatments were included four irrigation levels based on potential moisture 30-35 (I1), 50-55 (I2), 70-75 (I3) Centibar soil using Tensiometer and without irrigation (I4). The studied traits were included plant height, No. of nodes in main stem, No. of branches per plant, height of first pods from ground level, pod length, No. of pods per plant, No. of seeds in per pod, 1000 seed weight, seed yield and oil and protein content. Water productivity indices were also calculated. The results showed that deficit irrigation significantly reduced seed yield (Water deficit stress by reducing yield components decreased yield of soybean). The highest and the lowest value of the seed yield obtained by I1 and I4, respectively and also these two of treatments showed the highest and the lowest water productivity, respectively. So, according to the results of the present experiment, irrigation based on I1 treatment was recognized the best treatment in view of seed yield and water productivity. The results of correlation analysis showed high correlation between seed yield and No. of pods per plant (r=0.985**). The results of stepwise regression also showed that No. of pods per plant was the most important yield component and covered the most of total yield variance.

Estimating river sediment delivery is one of the important issues for researchers in hydrological studies because of its complexity. In a river that has sediment data in a few days per month, estimating of river sediment delivery is carried out by using sediment rating curve method. In this study in order to exactly estimation for such rivers, a new approach has been developed which it can be called as "Discharge-Sediment Relative Approach (DSRA) ". It is developed based on expanding sediment concentration continuity curve based on individual sediment concentration data in a few days of each month. In this method, the fluctuation of sediment concentration between two continuous measurements is reconstructed based on the ratio of the measured sediment concentration and water discharge. In this paper the DSRA method has been applied to estimate of Dez river sediment delivery as a case study. Also the amount of sediment inflow to Dez reservoir were calculated by using the USBR rating curve method. Comparison of calculated results with measured data obtained from Dez reservoir bathymetry showed that errors of the DSRA method to estimate of the annual sediment inflow to Dez reservoir was obtained as 8.5% while this value for USBR rating curve method was about 27%. This means that the DSRA Method could be considered as a good approach to estimate of river sediment delivery for gauged basins.

Phenomenon of land subsidence in recent decades has created many problems for agricultural lands, residential areas, roads and water channels in some of the plains in Isfahan province. The southern Mahyar plain is located in 50 km of southeastern Isfahan. It is one of the areas where the excessive withdrawal of ground water resources (mainly in the agricultural sector, based on available information) has substantially grown in recent years. The amount of water extracted from underground has increased from 58.8 million cubic meters (from 217 wells) in 1369 to 85.5 million cubic meters (from 446 wells) in 1388. The decline in water table increases the effective stress that causes consequences such as land subsidence and cracks in some parts of the southern Mahyar plain. To determine the effectiveness and ultimately to estimate the rate of subsidence, radar interferometry was used in this study. It is a reliable method to measure changes in the land surface, with very high accuracy, wide coverage and high spatial resolution. Maximum rate of subsidence was calculated at 8.2 cm/year using ENVISAT satellite radar images in the period of 2003-2006. The results of time series analysis showed that the land surface in the zone of danger is falling as a result of a decline in water table levels at a constant rate.

Water productivity Increase is one of the water management solutions in agriculture and increasing its efficiency. The accurate determination of plants water requirement and the accurate value estimate of evapotranspiration is essential for improving water productivity in irrigation network that it can help to improve water management in agriculture. This research was performed to determine the water requirement and crop coefficients of winter Gascogne wheat in station of estimating evaporation within three lysimeter in Ferdowsi university of Mashhad in Aban 1389. In general, the enough growth period of water was available to the plants and the amount of the water potential in soil was always at field capacity. The necessary data for measuring evapotranspiration was obtained the energy balance method at all stages of plant phenology in one-hour intervals from Aban to mid-khordad using energy balance device (DIK-2500). Based on the results, water requirement of wheat in growth period using energy balance and lysimeter methods was estimated respectively 536.5 and 544.5mm. Also, the water requirement of the reference plant was obtained 865.5 mm. The average of the crop coefficients of wheat was estimated 0.3, 0.8, 1.14 and 0.4 for the four growth stages.

This study was carried out to determine the effects of fertigation on clogging of emitters and drip irrigation systems performances. The experiment was done in the water scinces Engineering lab, university of shahid chamran, ahvaz, from 2010 to 2011. In the experiment, three different emitters (on-line and 2 type in-line) and three different fertilizer (urea 46%N) Treatments (no-fertilizer, concentration 0.05 gr/l and 0.08 gr/l) are used. In control treatment f0, showed emitters A, B and C respectively %17.9, %19.9 and %11.38 discharge rate decrease. In treatment f1, showed emitters A, B and C respectively %22.8, %26.48 and %17.14 discharge rate decrease. In treatment f2, showed emitters A, B and C respectively %25.25, %33.67 and %19.16 discharge rate decrease. The results showed that the increasing of fertigation concentration, results in increasing clooging emitters. Clooging emitters decrease emission uniformity (Eu), Christiansen, s uniformity coefficient (Uc) and increasing of emitter discharge variations coefficient. Emitters that have the lowest flow rates had the lowest performance. These changes were different for all three type of emitters. The results showed thowed that emitters with code B were most sensitive to fertigation. Overally, sensitiveness to fertigatiuon were decreasing for emitters B, A and C respectively. Increase in concentration of irrigation fertilizer has a strong effect on the discharge of emitters and coefficient of discharge.

Problems related to sedimentation and depositions can be minimized by using a system where weirs and gate are combined in open canals while the floated materials run over and sediments run under the structure. Because of effect of overflow on underflow, the variation rate of discharge coefficient with geometric and hydraulic parameters is different with their use each other separately. It is important for cylindrical weir-gate because the flow nape will sit on the weir completely the current work describes the results of experimental investigation on effect of weir flow on gate discharge coefficient for cylindrical weir-gate. In this way the gate discharge is measured against upstream water depth in two condition of weir flow and without weir flow. The experiments are carried out in a laboratory flume 10 m length, 60 cm wide and 70 cm height. Results indicate that increasing dimensionless parameters of Hw/a and Hw/D cause decreasing the discharge coefficient for weir flow and it rises about 1-25% without weir flow. For a constant values of the Hw/a increasing the gate height, the effect of weir on gate discharge coefficient decreases for the cylindrical weir-gate.

Study of drought situation is important in various areas in editor plans to deal with the drought and risk management. Rainfall is one of the most important variables that are used in defining drought. Several index is presented to assessment for drought based on rainfall. Study simultaneous occurrence of certain classes of states of the drought index can be appropriate criterion for conformity assesment indicators. The purpose of this research is study the performance indexes of drought in Sistan and Baluchestan province, and select the appropriate index. To achieve this goal, used of data annual rainfall from 1360 to 1389 and using an index of normal (PN), The rainfall deciles (DPI), the Standardized Precipitation (SPI), Precipitation anomalies (RAI) in 7 meteorological stations in Sistan and Baluchestan province, drought have been studied and was classified. To select the most appropriate index was used of sperman correlation coefficient between the index drought and rainfall changes in the period under study. Results showed that, in cities Zahak, Zabol, Iranshahr and Chabahar PN index with correlation coefficient (1), in the cities of Zahedan and Saravan RAI index by coefficient 0.84 and 0.99 and in Khash SPI index by correlation coefficient (1) could show very severe and extreme drought better than other indicators. In evaluating the correlation between paired indicators, PN-RAI, PN-SPI and SPI-RAI have a high correlation to each other the Possibility level (p<0.01) in most of stations.

Prediction of water table depth and outflow rate of drainage system are the most important issues in the literature of the drainage engineering. Three models of Kraijenhoff Van de Leur– Maasland, de Zeeuw - Hellinga and Glover – Dumm are frequently used for prediction of water level and discharge rate under unsteady state flow condition. For comparing the ability of these models an experiment was conducted using a laboratorial physical model. Data were collected for constant and variable head conditions in accordance to the boundary conditions of each model. The results showed good agreement with the observation data. For water level rising condition the Kraijenhoff Van de Leur – Maasland and de Zeeuw – Hellinga models, underestimated the outflow rate and overestimated the water table level as compared to the observed data, also Kraijenhoff Van de Leur – Maasland model's prediction was better than that of de Zeeuw – Hellinga model. For the falling water table state the de Zeeuw – Hellinga model prediction was closer to the observation. The prediction accuracies of all three models decreased and converged while reaching the end of the experiment.