Journal of Irrigation Sciences and Engineering
Year:2015 | Volume:38 | Issue:1|Papers Count:13

One of the potential advantages of drip irrigation is allowing the use of fertilizer and poison with irrigation water. In this study, the effect of fertilizers on clogging dripper and drip irrigation system performance has been investigated. This study in a randomized block design framework was done that its factors were three treatments of fertilizer (ammonium phosphate) includes treatment F0 (control), and a F1 with concentrations of 5 g/l, respectively, and three dropper treatment (the in line long path and two outline long path). Dropper with codes A, B and C were named. In order to investigating dropper clogging, reduce discharge rate, efficiency of uniform distribution, Kristiansen uniformity coefficient and coefficient of discharge variation was calculated. After test period the percentage of reduce discharge for droppers was obtained 19.9, 20.78, and 11 percent for treatment F0 (control) respectively, and 26.48, 26.49 and 16.65 percent for treatment F1, respectively. The results were shown increasing concentration of irrigation fertilizer caused increasing dropper clogging and have a significant effect on Changes in discharge.

In present study the effect of obstacles transversal distances in a staggered and an in-line arrangement on suspended sediment load transport in a rectangular flume was investigated. The results show that in transverse wave condition, the concentration of suspended sediment at downstream obstacles zone is more than the part of no obstacles zone but it was reduced in the case of existing transverse wave and in the same condition of discharge, diameter and perpendicular distances, increasing of obstacles transversal distances causes to increase of this difference but with no significance at 5% level. Although, in mentioned condition, increasing of obstacles transversal distances caused to decrease the percentage of transported suspended sediment concentration in obstacles zone in an in-line arrangement and this decreases was significant at 5% level. But the percentage of decreased suspended sediment concentration was decreased with no significance at 5% level in a staggered arrangement for wave modes 1 and 2. By increasing of obstacles transversal distances, the percentage of increased suspended sediment concentration which transported in no obstacles zone for wave mode 1 was not changed in both staggered and in-line arrangement. Although, the transportation of suspended sediment concentration was increased for wave mode 2 in a staggered arrangement but it was decreased in an in-line arrangement, so in this condition, suspended sediment was deposited at upstream of obstacles zone.

Spur dikes are hydraulic structures, which are built across the river from river bank towards centerline in order to protect the river bank from erosion, natural development of amending the river side, special protection of local structures, navigation and environmental rehabilitation of river. The main job of these structures is to divert the flow away from the bank and towards centerline of river. However, the velocity will increase and the complicate vortex will be formed around the spur nose and the protection of spur dikes against scouring and their stability is very important. Using riprap is the most common and economical method for spur dike protection. In this study the effect of relative height and length of the submerged spur dikes on riprap stability is investigated. The experiments were carried out in a laboratory flume with 90o bend and R/B=4.0. Six sizes of ripraps including 5.5, 7.9, 11.1, 14.3, 17.9, and 22.2 mm, with three relative spur length (15%, 20% and 25% of the flume width) and four dischrge (25, 29, 32 and 36 lit/s) were used. The results showed that the larger riprap failed for the higher relative spur height. With increasing the relative spur length the riprap stability decreased.Finally an experimental equation was developed based on the relative spur height and length and riprap size, which can be applied for designing of riprap size.

Lettuce of Ahvaz (modified) with a scientific name Lactuca sativa varieties Romaine or Cos has one of the highest yields among the different types of country. In this study, the lettuce yield under different treatments was evaluated. The statistical method of this research is factorial design in a randomized complete blocks that major factor is irrigation frequency includes A1 and A2 (1 day and 2 days) and minor factor is irrigation regime that includes B1 and B2 (100% water requirement and 80% of the crop water requirement).This experiment was performed in 4 replicates. For this research, 4 chasis in the greenhouse is devoted that plays a rol of replicate. Each block consists of the 12 plants on a row crop that were irrigated by a drip irrigation lateral tape type. For irrigate the crops was used the drip irrigation with tape type, emitters spaced 20 cm diameter of 20 mm. Soil moisture was measured with TDR device. In this experiment, lettuce height was measured during the growing season and the relationship between plant height and number of days were presented with a high correlation. Also water use efficiency was measured. Results showed that irrigation frequency under greenhouse conditions did not cause significant difference on the water use efficiency. Reduction the amount of irrigation water caused that water use efficiency increased significantly. So that the best water use efficiency was happened in the treatment of 80% water requirement with irrigation frequency 2 days to the amount 25.02 kg/m3 and the minimum water use efficiency was happened in the treatment of 100% water requirement with irrigation frequency 1 days to the amount 16.89 kg/m3.

Irrigated lands of Khuzestan are lands with shallow and saline groundwater, in which water losses of deep percolation during irrigation cause that irrigation water, because of the density difference, floats to the top of saline aquifer creating a fresh and saline water mixing zone. In new drainage issues such as reducing the depth of drain insertion aimed to an optimum use of water, dynamic studies on this region and evaluation of factors affecting its features are necessary. In the present study, two farms of sugarcane in south Khuzestan with two different drainage depths were selected. During the study, for each farm, installing pisometers at various depths and different distances from drain collector, the water level inside the pisometers and groundwater salinity were measured. Results indicated that by starting a heavy irrigation, hydraulic load is increased and hydraulic load variance between bottom layer (4 and 5 m) to the surface one (1 and 1.3 m) creates a vertical flow of saline water. As well, by reducing the drain insertion depth and increasing the distance from drain collector, in addition of the increase of hydraulic load to 10-15 cm, mixing zone`s thickness increases to 1 m and the mean salinity line in this region reduces to 5-10 percent. But, as well, this region`s features depend on the depth of impermeable layer and existence of sand lenses, as with low depth of impermeable layer and existence of sand lenses, because of the hydraulic load`s lack of increase, mixing zone`s thickness, is reduced and the salinity is highly increased.

Understanding the changes in groundwater quality has an important role on the planning and sustainable management of water and soil resources in any region. In this study, trends of groundwater quality of Shabestar - Soofian plain using the information of the 18 deep wells and four Qanats were analyzed during 1998-2011. For this purpose, the non- parametric Mann – Kendall method were used. Before conducting the MK test, the effect of significant lag-1 serial correlation was removed from the data set. Hydro - geochemical variables that analyzed were the total Anions, total Cations, pH, EC, SO42-, Na%, Na+, Ca2+, Mg2+, TDS, SAR, Cl- and HCO3- which were measured twice in a year, wet and dry periods. The magnitudes of trends were computed using the Sen’s estimator method. Change points identified using the Pettitt test. Results showed that in most of the Qanats many variables showed decreasing trends and some of them showed increasing (but insignificant) trends. In the wet period, 21 percent of the stations and in the dry period, 22 percent of the stations experienced significant increasing trend in more than half of the variables. Results of trend line slope showed that in wet period groundwater quality is going to be improving but it is not true in dry period. Increasing trends observed in both periods in the southern plain overlooking the Urmia Lake. The steepest trend line slope belonged to the Shendabad (Farahnak) station, which was about 400 mS/cm. Among the whole of the time series about 63 percent of them experienced significant trends (in unsuitable direction).

Water resource limits, missing a developed irrigation program and undesirable water quality are the basic parameters that affect agricultural development of Iran. This research focus on irrigation amount water and its duration in other to increase crop yield of wheat on Hamedan-Bahar and Razan-Ghahavand plains. To this regard, three wheat farms located on different area of the plains were selected during agronomic year 2011. Consumption water amount (W) and crop yield (Y) were measured in order to calculate the water use efficiency (WUE) of the farms. The results showed that wheat yield significantly was increased (21.6%) by training of proper planning program of irrigation. This increasing yield resulted decreasing on using water content (23.1%) and increasing of water use efficiency (55%) in all farms of the experiment. The farmers training also showed that tensiometer is a simple and favorite instrument for optimal water using compared with gypsum blocks.

In this study reservoir inflow volume is used to investigate drought conditions by various methods so that by comparison with drought conditions at meteorological and hydrometric stations, the used drought indices could be evaluated. Also, relationships between cumulative reservoir inflow volumes at critical dates and those of the previous months were investigated, in order to identify effective variables for future utilization of stored water and implementation of optimal management decisions for reservoir operation. At first, the SPI was used in two different manners, by applying the method by Mckee and also by applying the method by Nalbantis and Tsakiris, in order to investigate meteorological droughts in four rainfall stations at Kor watershed (upstream of Doroodzan Dam). Also, hydrological drought conditions were investigated based on data on inflow into the Doroodzan reservoir and Chamriz hydrometric station, which were modeled utilizing the SDI, which according to the results the SPI and the SDI from the hydrometric station data, would not be sufficient for drought monitoring and utilization of the SDI on inflow into the reservoir as a good representative of the entire watershed would be more appropriate. In order to establish relationships between cumulative reservoir inflows at critical dates with cumulative reservoir inflow of previous months, the first days of Farvardin, Ordibehesht, Khordad and Tir were considered as critical dates. According to final equations, inflow into the reservoir on the first days of Ordibehesht, Khordad and Tir are directly related to cumulative inflows of the previous month. This would indicate that as the non-rainy season approaches, inflow volume stabilizes and is less effected by rainfalls or in other words by climatological factors. Whereby, for the first day of Farvardin, month of Mehr along with Dey and Bahman as effective variables indicates that inflow volume on the first day of Farvardin is dependent on the rainy season, which would highlight the importance of drought indices and also climatological factors on reservoir inflow during the rainy season.

Flood and drought analysis accuracy and estimating return period of droughts depend on selecting type of distribution functions and method of estimating parameters. In this study daily river flow of Nazloochai, Barandouzchai and Shahrchai rivers in the historical and predicted series used to estimate river drought volume series up to 60 days duration in the predicted and actual series. Then using log-Pearson type III distribution function, drought volume of the historical and predicted flow series for the return period of 1 to 10.000 years estimated. Results indicated that drought intensity of Nazloochai and Barandouzchai rivers reduced while in the Shahrchai river drought volume increased in the updated statistical period of data. As updated charts showed 60 days duration drought volume of Barandouzchai and Nazloochai rivers with the 10000 year return period reduced about 29 and 62 (mcm) respectively while for Shahrchai river it is increased about 7 (mcm).

Evaluation of dispersivity in different soil textures can be used in solving problems related to pollutants migration of groundwater. Numerical models are frequently used for simulation of water movement in soils. In the present study, the dependence of dispersivity on the soil texture has been investigated. The textures of soils consisted of medium sand particles and medium sand particles with 25, 50 and 75 percent (by weight) of coarse sand and coarse designated by T1, T2, T3, T4 and T5 with 40 cm height of soil column respectively. For calculation of dispersivity Brigham model and for simulation of salinity movement HYDRUS software used. Results of the study indicated that the dispersivity of sandy soil was dependent on the particle size and mixture of textures. And with increase of coarse soil, dispersivity increased.

The present study was conduct in order to surveying the efficiency of Chitosan in performance improvement of coagulant of poly aluminum chloride in removing the turbidity, Al, and organic materials including TOC and UV254 (Absorption of the organic materials by ultraviolet at 254 nm) at the slow mixing phase from drinking water. This study conducted in the labscale using jar test device in water treatment plant of Ahvaz. Optimal dosage of poly aluminum chloride together with chitosan was obtained 5 mg/L and 0.02 mg/L respectively. The efficiency of removing the turbidity, TOC, Al and UV254 in the optimal conditions of Chitosan performance were obtained for 96.59, 46.15, 80.49, and 67.86% respectively. The dominant mechanism for instable making colloidal particles and removing the natural organic materials by bridging between the particles-polymers, neutralizing the colloidal NOM charge, and common deposition mechanism by surface absorption are justified. In addition, floces formed by chitosan were coarser due to the high molecular weight and needed to the less time in order to being deposited.

Sepiolite is a low-cost mineral widely distributed in arid regions of the world. Due to the structural properties, sepiolite has high sorption capacity for heavy metals. The objectives of this study were to investigate the effects of solution temperature, initial pH of suspension, contact time and dose of Iranian natural sepiolite on the removal efficiency of lead from aqueous solutions. Before use, sepiolite powder (25-53 mm) was saturated with calcium and the specific surface area and cation exchange capacity was determined. The experimental data were fitted with pseudo first order and pseudo second order kinetic models. Results obtained from kinetic studies indicated that pseudo-second order model better fitted to the experimental data. The results also implied that with the increasing contact time more amounts of lead ions were adsorbed by sepiolite. Similarly, with the increasing the solution temperature from 20 to 40 ˚C the adsorption rate of lead by sepiolite decreased. Furthermore, the results indicated that increasing the pH of solution from 3 to 9 and dose of sepiolite from 2 to 16 g l-1 increases the adsorption efficiency of lead ions from the aqueous solutions.