Iranian Journal of Irrigation and Drainage
Year:2008 | Volume:2 | Issue:2|Papers Count:16

One of the most significant consequences of climate change is its impact on agricultural water demand that is considered as a serious challenge for the future of water resources. In this research work, a number of the AOGCM models including: CCSR NIBS, CGCM2, CSIRO MK2, ECHAM4, OPOYC3, GFDL R30, HadCM3 and NCAR DOE PCM (A2 emission scenario) are processed to evaluate the impacts of climate change on agriculture water demand in Zayandeh Rud irrigation networks for two time periods: 2010- 2039 and 2070- 2099. The selected crops are wheat, barely, sugar-beet and potato, which are the basin's major crops. Due to uncertainty associated with different AOGCM models, the ranges of temperature were calculated from the referred models and used to determine the climate change scenarios. Then for uncertainty and risk analysis, 1000 samples of time series for horizon of 100 years produced and in the sequel, water demand and the risk of it's changing considered. The results showed significant increase in temperature. Based on the different models results, an increase.in water demand of agricultural sector will be inevitable and uncertainty and risk will be involved. The study also revealed significant increase in agriculture water demand at the end of this century that necessitates adaptation strategies to mitigate the impacts, especially for the 2070-99 period. Considering the present areas of the selected crops and their augmented requirements, volumes of 173 to 230 MCM/y (for the probability of %50 and 0/025) will be required to meet the demands. Finally, it is found that responses of the crops were different where potato tolerates more variability to this phenomenon.

The Result of field experiments on surface irrigation in khorasan Razavi province shows that the efficiency application in initial growth stage of plants is very low and less than 10% but after that stage, that maybe bigger than 90%.In order to investigate on the effect of the replacement of current surface irrigation system to drip irrigation on amount of water consumption, yield and water use efficiency (WUE) a study was conducted in some personal farms of Khorasan Razavi province in 2006. The results of analysis showed that the maximum and minimum of yield percentage increased for potato with 21% and sugar beet with 9% respectively. The most saving in water consumption was observed in green com cultivation and the minimum amount of that was happened in tomato farms respectively with 49% and 34%. Water use efficiency in green com increased to 116% and tomato, sugar beet and potato cultivation respectively with 98%, 92% and 83% were located in the next stages. Overall in all farms, the average of used water irrigation, in the total sugar beet, green com, tomato and potato farms, have been reduced from 34% to 49%, whereas the amount of average yield of the four mentioned product increased by 9% to 21%, as well as 83%to 116% (about two time more) for WUE. Surface of planting of sugar beet, potato, green com and tomato increased to 76, 51, 95 and 65 percent respectively and the rate of return of investment of them was 389, 456, 748 and 1304 percent respectively.

The sprinkler irrigation is a method that due to its high performance and saving of water is expanding. In sprinkler irrigation it is possible to store some parts of irrigation water at soil surface without runoff. The soil surface storage depends on slope, crop coverage and roughness. Surface storage has important influence on runoff and infiltration. In cracking clay soils, with reduction of soil moisture, cracks are developed which cause problems for infiltration and irrigation performance. In this study, to determine the effects of slope (1, 3 and 5%), crop coverage and soil cracks on surface storage and runoff under a typical sprinkler irrigation system, field experiments were conducted on a sprinkler irrigation farm at Markazi province, central Iran. The experiments were conducted for two soils (ordinary and cracking clay) using complete randomized design with three replications for each treatment. The results showed that slope and crop coverage have significant effects on runoff and surface storage. The increase in slope from 1% to 5%, caused the runoff to increase from 34.7% to 43.3%. The effects of slope on surface storage were negative. In ordinary soil without crop coverage, the increase in slope from 1% to 5% caused the depth of surface storage to decrease from 0.97 cm to 0.58 cm. The crop coverage caused 10% reduction in volume of runoff. The effects of crop coverage on runoff were higher as compared to the effects of soil cracks. The effects of soil cracks on surface storage were significant at 5% level.

The soils of paddy fields of Guilan province, due to a large amount of clay particles, shrink and the cracks will start to develop as the soil moisture content decreases, which causes a considerable amount of irrigation water loss through the cracks. Appropriate irrigation management of these soils has important influence on reduction of irrigation water loss. This study was performed to determine the effects of different irrigation water managements on amount of irrigation water and infiltration characteristics of paddy fields in a dominant swelling soil of Guilan province. The experiments were factorial completely randomized block design with three replications. The main treatments were crack width (3-4 mm, 1.5 cm and 2.5 cm) which are called C0, C1.5 and C2.5, respectively. The sub-treatments were irrigation, with irrigation to fill up the cracks and up to the start of ponding, irrigation to fill up the cracks and up to 2.5 cm of ponding at the soil surface and irrigation to fill up the cracks and up to 5 cm of ponding at the soil surface, which are called D0, D2.5 and D5, respectively. The results showed that the initial soil moisture content has important influence on infiltration of cracking soils and a large portion of irrigation water will be used to fill up the cracks. The soil moisture changes have low influence on the exponent and high influence on the coefficient of Kostiakov-Lewis infiltration equation. As the soil moisture decreased, the coefficient of this equation increased and larger volume of irrigation water was needed to fill up the cracks. The cumulative infiltration for the C2.5 treatment as compared to the C0 and C1.5 treatments was 4.34 and 2.35 times higher, respectively. The effects of crack width, depth of irrigation water and the interaction effects of crack width and depth of irrigation water on volume of irrigation water were significant. The irrigation water loss for the C0, C1.5 and C2.5 treatments were 56.73, 64.53 and 78.17%, respectively.

The rainfall is an important parameter in the water resources research. Hence it is necessary to available an adequate raingage network that enable an exact estimate by its rain measurement.In this research for optimizing the Khozestan province raingage network, between the different estimating method, Geostatistic method and invert distance method compared. The indicator for comparing methods is Mean Square Error (MSE). Mean Absolute Error (MAE) and Mean Bias Error (MBE) that are result of Crosse validation technique.The data set include of monthly rainfall of 79 number of raingage network. Result of studies showed that the kriging method estimate the rainfall with high accuracy. Thus kriging method used for optimize the rangage network. Because of none correlation between height as a helping variety and monthly rainfall, the cokriging method is not an adequate method. Gaussian model between the available fitting models had the best fit.to study the addition raingages, using tow evaluation indicator of cross validation technique, S number of raingage that were estimable by other point of network had been suggested for removing from raingage network. Also for decreasing the estimate error of monthly rainfall in the new raingage adding stage at the region, by evaluation the kriging estimate error, three new point for create the rangage were selected.

Cotton is the plant that shows different response to amount of irrigation water so that increasing of water not only causes increasing the yield but also sometimes decreasing the yield. This experiment was conducted by sprinkler irrigation system as line-source because of water shortage in Golestan provience, necessity of optimum use of water unit and effects of water deficit on yield and yield components. Since distribution: of sprinkler water was triangular, six irrigation treatments of 11, 12, 13, 14, 15 and 16 was assumed in two side of sprinkler line as parallel and 2.5m distance, so that 11 and 16 treatments received highest and lowest water amount, respectively. The amount of received water in 12 treatment was equal to water requirement. Therefore, irrigation levels treatments were 125, 100, 73, 60, 39 and 20% of water requirement. Cotton varieties of Sahel, Sepid and 818- 312 were planted by distance 20cm on planting rows and 80cm between rows. The experimemtal design was strip split plot with 3 replications. The results showed that highest yield was belonged to 13 treatment with 3365 kg/ha in 2001 year and 2043 kg/ha in 2002 year. There was significant difference between 13 treatment with 14, 15, and 16 treatments in the first year and all treatments in the second year on view of the yield. Increasing and over decreasing of amount of irrigation water decreased the yield. The yield of Sepid varietiy was 17.9% higher than two other varieties in the first year and 15% higher than Sahel varietiy in the second year. Difference between three varieties on view of earliness percentage was not significant and also on view of boll weight in the first year was not significant but in the second year it was significant. The highest boll weight was belonged to 13 treatment and treatment 16 had highest earliness percentage. Water use in 13 treatment was 27% less than water requirement. Ultimately, the best treatment and variety on view of yield, yield components and water use saving was 13 irrigation treatment which used 73% of water requirement and sepid varietiy.

A large amount of rainfall and irrigation water in arid and semi-arid regions is lost through soil Surface via evaporation. In the vegetated areas, depends on the plant type, growing stage and irrigation methods, about 10 to 69 percent of the total evapotranspiration belong only to evaporation. In such regions with shallow ground water table, high evaporation leads to accumulate salts at the soil surface. Thus, the evaporation phenomenon not only is responsible for water loss but also is a major factor for soil salinization. One major difficulty for accurate estimation of evaporation in the field conditions is lack of simple function with less needed input parameters. The main purpose of this study was to compare three analytical solutions for one-dimensional non-steady upward flow from falling shallow ground water table to the soil surface with minimum input data. These analytical solutions were derived based on the Richards' equation with the initial and boundary conditions governing evaporation process. The solutions were based on the parametric equations of Campbell, Brooks – Corey and the closed from function of Van Genuchten for soil water characteristics. One equation has been obtained for each retention curve, using Richard's equation. In these solutions, the amount of evaporation from the soil surface can be estimated as functions of water-table drowdown and some soil physical properties. Some experimental soil columns with packed silty clay, silty clay loam and sandy loam soils were carried out to evaluate the derived analytical solutions. While the results indicated reasonable agreements between the observed data and the models outputs, some small discrepancies were also observed. The analytical models were appeared to underestimate the evaporation for a certain period of time. The results also showed that the obtained values with the Van Genuchten's function can provide better prediction than the Brooks - Corey's and the Campbell's models, respectively.

The prediction of transport flux process in soil is important and vitual in many of soil science branches and environmental. preferential flow is one of the mechanism of water and solute transport in soil. These pathways are created by movement of earthworms or decomposion of roots or swelling and shrinkage of soils. The aim of this research is the study of preferentially flow of nitrate ion in soil with and without macropores under two water fluxes of 0.3 Ks and 0.7 Ks (Ks is hydraulic conductivity of saturated soil). For this purpose two kinds of soils, loamy and sandy clay soils were chosen. Disturbed column soil with 30cm hight and 20cm diameter were prepared. The bulk density of soil in columns were as the same as undisturbed soils, 16 columns of soils were prepared, the treatments were 2 different soil textures. 2 water fluxes, with and without macropores with 2 replicates. The resukt showed that in soil columns without macropores BTCs had only one peak which means preferential flow did not occure in both soils. But in columns with macropores, preferential flows occurred and two peaks appearrrred. The first one showed preferentially movement of nitrate ion through macropores and the second one showed nitrate transportation among soil matrix. Increasing flixes from 0.3 Ks to 0.7 Ks, the preferential flow increases. But some times in sandy clay loam soil preferential flow did not occure. Probably it is due to collapsing of macropores and sealing of these pores.

Continued usage of gravel envelope for drain pipes is encountered with difficulties such as preparing, transport and unjustified cost efficiency. Therefore, use of geotextile filters which cost less and have less problems are being more widely recommended. This study deal with the evaluation of three synthetic drain envelope's filter performance as compared with conventional envelope. First, soils samples were collected from 2 different region from the study site. According to the physical and chemical evaluation of soil samples they were basically the same. Therefore the study was done on a single sample. Next, 3 types of geotextile filters of pp450, pp700, pp900 which has been found suitable were selected. A gravel envelope according to USBR standard was also selected. A standard permeameter was used at 4 different hydraulic head (25, 50, 75, 100 cm) for the test. Variation in drain flow rate, hydraulic conductivity, gradiant ratio, relative hydraulic conductivity were measured. Based on the results of this study we conclude that none of the filters (gravel or geotextile) were susceptible to clogging. Drain flow rate through the gravel envelope were nearly twice as much as the flow through geotextile filters. The pp450 filter were to have the best performance and is recommended for this situation. Geotextile filters were found to be more appropriate for cases where water table is to be lowered slower to maintain more moisture storage.

The use of pesticide and fertilizer has been very widespread in agricultural from the last five decade. Buildup of injurious chemical density in surface and groundwater resulted from poor management in irrigation and fertigation in agricultural. The bad management in application of chemical fertilizers in agricultural is hazardous, therefore in order to increase the yield and reduced resources water contaminations, the irrigation and fertigation management is essential. A research was conducted in an area of 32.1 ha under center pivot irrigation system (low pressure system) in order to determine the optimal irrigation depth assessment base on three different economic management strategies. The values of economical ratio (C) were determined 20.01, 3.21, and 1.13 for three different management strategies such as unlimited, limited fertilizer leaching, and limited environmental protection respectively. The results showed that the values of optimal irrigation depth for three irrigation water management strategies (assuming exponential distribution) were 8.32, 13.33, and 17.98 mm respectively.According to the obtained results of this research, an unlimited economic management strategy is recommended under deficit irrigation water or draught conditions.

Runoff and soil erosion from agricultural farms is one of the important phenomena because of its impacts on farm fertility. In this regards, type of the irrigation system has the great effect on runoff and soil erosion. Sprinkler irrigation with traveling rain-gun may causes runoff and erosion on field. One of the essential measures for controling and reducing of runoff and soil erosion under gun sprinkler irrigation is simulation of this phenomenon. In this regard EUROSEM model is one of the computer models. However applicability of the model should be assessed. In this research efficiency of the EUROSEM model for estimating runoff and soil erosion has been evaluated by using field investigation in a research farm with two slope land of 1 and 3 percent located in shahrekord University. Experiments were conducted under rain intensity of 38 mm/hr averagely with coefficient of uniformity of 89.5 percent.Results show that runoff and soil erosion can be successfully modeled by EUROSEM model; but the model to estimate time of starting hydrograph and time of peak flow has more errors. The results show that accuracy of the model to estimate runoff and sediment production is parallel and it was not shown significant difference between estimating of the parameters. In addition, verification procedure of the model shows that if the model to be calibrated for a certain event; one can simulate other events successfully by using the calibrated model. This means that the number of filed measurements can be reduced via application of the model.

The research was conducted in the four fields with Center pivot irrigation system in the Bardsir region during the cropping years of 2001-02 and 2002-03. Water productivities (WP) of the major crops of the region, including Wheat, Sugar beet, Maize, and Alfalfa, were determined in the selected fields. Then using economical evaluations, the economical efficiency and monetary productivity index per unit volume of applied water were calculated. For determining water price, the relationships of water withdrawn and conveyance costs were used.Results indicated that the maximum and the minimum WPs belong to the Maize (9.98 kg/m3) and Wheat (0.11 kg/m3) respectively. The ultimate price of water, considering interest rate of 15%, for the four fields were 205, 323, 146, and 237 Rials. Using the WP values, the monetary productivity index of water for the different crops were determined. This index for the Wheat, Sugar beet, Maize, and Alfalfa ranges between 2.4-6.1, 3.5-8.8, 5.4- 6.5, 4.3-6.5 respectively. Then, using the values of monetary productivity index of water, cropping priorities of the crops in the selected fields were determined. Sugar beet and Maize were the first priority crops in the fields no. 1, 3, 4 and the field no, 2 respectively. In all the selected fields cropping of the Wheat had the lowest priority.

Prediction of annual precipitation usually guarantees success in dry-farming, design and operation of water resources, better regional economic programs and pasture management. Kerman province is located in the south east of Iran where more is covered by high mountains and pastures. Agricultural production and farmer economic statues in. these regions are highly associated with annual precipitation. Therefore, a method for predicting annual precipitation in the beginning of water-year could be useful.The studies have been resulted good relationships between annual precipitation and the duration which is needed to occur a definite amount of precipitation since the onset of autumn (beginning of water-year; October to September) in some part of Iran. Karimi and Sepaskhah (2006) have reported significance linear relationship between annual rainfall and the duration of 47.5 mm of precipitation since the onset of autumn in Kerman province. They developed a linear model to predict the annual rainfall too. Similar results have been reported by Sepaskhah and Taghvaee (2006) for west of Iran.Different procedures have been used to predict rainfall. Rainfall forecasting is an extremely complex and difficult problem involving many variables which are interconnected in a very complicated way. Most of the relationships describing the dynamical and spatial relations are nonlinear. This complexity and non-linearity makes it attractive to try the artificial neural network (ANN) approach which is inherently suited to problems that are mathematically difficult to describe.Neural networks were originally developed as a model of information storage and computing by neuronal processes found in nature. Details of emergent computational properties of such artificial neural networks are discussed in many texts. The use of neural networks in the hydrology is dramatically increasing, and includes applications to problems such as rainfall-runoff modeling (Shamsedin, 1997) and reservoir inflow forecasting (Coulibari et al., 2000). The ANN methodology has been applied also to forecast rainfall; for example, French et al. (1992) used synthetically generated rainfall storms to calibrate an ANN model and then generated plausible rainfall sequences that could occur over a catchment using a physically based rainfall to validate the ANN. Based on author knowledge there is no published report about the ability of ANNs to predict the rainfall south east of Iran.The present study was conducted to develop linear and ANN models to predict the annual precipitation in Kerman province based on prior knowledge of relatively good relationship between the numbers of rainy days from the beginning of fall for total precipitation of 47.5 mm with annual precipitation.

Groundwater resources are considered as one of the significant and economical water resources. Comprehensive recognition and proper utilization of this valuable resource especially in arid and semiarid areas has an important effect on sustainable development of social and economic activities. It is necessary to predict groundwater level fluctuations for a better understanding of the aquifer behavior in these areas. This research was aimed at prediction of groundwater level in Neyshabour plain using "Panel Data" model. The plain was selected due to presence of over 50 observation wells, mostly with more than 12 years of record. Inasmuch as "Panel Data" model considers historic data for several observation wells, it was able to predict groundwater levels in different observation wells simultaneously. At the first step, the available observation wells in the plain were clustered with "Ward" method which ended-up in six areal zones. Then, for each cluster, an observation well was selected as its representative, and for each zone, values of independent variables (precipitation, temperature, and initial water table) were estimated by "Distance Inverse method". Finally, the performances of different Panel Data regression models such as Panel Data with Common effects, Fixed effects and Random effects, for groundwater level prediction were investigated. The results shows Common effects model has the best results for prediction of groundwater level. The performance indicators (R2: 0.99 and RMSE=0.05) reveals the effectiveness of this method. In addition, these results were compared with the results of an ANN model, which showed relevant superiority of "Panel Data" over ANN.