مجله آبیاری و زهکشی ایران
سال هفتم شماره 4 (زمستان 1392)

Assessment of effective climate parameters and planning for their managing and or arranging agronomic activity with those trend changes, that result to improving production baseline and prediction for future. In order to determination of climate-yield production functions, analyzed eight crop seasons data (1998-2006) of 25 climate parameters and rainfed barley grain yields of four cold and semi-cold regions of Lorestan province.These regions were including Kohdasht and PoleDokhtar regions. By path analysis method, correlationcoefficient separated to direct and indirect effects. Results showed that in local and common models ofproduction functions, the role of crop season vapor pressure deficit is very important. The local models necessary small input data but common model need more input data (Tmin, RHmean, n, PWinter, PStart, Pend, Tmin-abs, PAzar, PDay, PFar., POrd., Tmax-azar). Rain water productivity of all regions determined for eight crop seasons, and amounts of maximum, minimum and average of rain water productivity were 0.422, 0.137 and 0.304 kg per cubic precipitation, which its average was 27.2 percent more than national average (0.239 kg.m-3). The sunshine,minimum temperature, average relative humidity, start rain and winter precipitation parameters, were the most sensitive parameters on barley grain yield prediction. We conducted the climate-yield models are useful tools to predict rainfed barley yield and so to assist managers and farmers for making decisions in rainfed agronomic activity under climate parameters changes.

Successful soil reclamation requires to leach out the excess soluble salts from the soil profile when the natural soil drainage condition is proper for this purpose. At absence of such drainage system, a surface or subsurface drainage system must be installed. In spite of advantages involved in using drainage systems with relatively shallow depth, the environmental consequences of discharging pollutants remains to be a considerablechallenging factor for the integrity of surface and subsurface water bodies. This problem is partly to do with inaccurate estimation of real drainage flow discharge in a way in which the estimated drainage discharge concentration is much lower than real value. This article focuses on introducing an applied method by which drainage discharge at two levels at the top and bottom parts of the drainage structure with different concentration is affected. The methodology involved using three soil texture types (light, medium and heavy),four subsurface water salinities(8,16,24 and 32 dS/m),with three soil impervious layers depths(2.5,3 and 3.5m),three deep drainage coefficients (2,2.5 and 3 mm/day) and also combinations of the mentioned conditions. The subsurface drain spaces for four different depths (1.5, 1.6, 1.7 and 1.8 m) under steady state conditions with the designatedcrop pattern for annual cropping rotation in Khuzestan province climatic conditions were estimated. These were simulated with a computer program and the results were compared with the observed real data. The obtained results indicated that deepening of field subsurface drainage system does not have significant differences inachieving chemical equilibrium between the irrigation water and drainage outflow. This can be attributed to some economic and technical advantages. Quantitative assessment of the simulation results substantiates the reliability and validity of the proposed model.

Reference Crop Evapotranspiration (ETo) is one of the most important component of hydrologic cycle. It is estimated either through lysimetriy or by empirical equations. Hargreaves-Samani (H-S) is one of the simplest methods that needs only to temperature data (minimum and maximum daily). The purpose of this paper is to find the best correction factor applying to H-S method that translates to the assumed true Fao Penman Monthis method for synoptic stations of Khorasan Razavi Province. Such a correction factor, however, is taken constant in nearly all of the published papers, which demands for local-nature. Here, it is considered as a function of those meteorological variables available at evaporation stations, considering temperature and humidity ones, and some regression equations were derived. The parameters of these equations, based on the results, were not constant for different synoptic stations, which confirms for non-constant correction factor. Different equations were ranked based on 7 different evaluation methods and the best equation was found for each synoptic station. Influenceregion for each synoptic station was determined and evaporation stations within each region were determined.

Water restriction is considered as main obstacle to the crops production, especially wheat. In this study the effect of water stress at different growth stages and different cultivation methods studied on yield of winter wheat N 80-19 in silt - loam soil. This experiment was done in Factorial with complete randomized block design with three replications. Water stress treatments were consisted of control (no water stress), stress in the development, midseason and final stages. And cultivation methods treatments were included flat basin, furrow method and roller furrow. Irrigation water was applied according to needs of soil moisture demand to field capacity point at different stages of growth. Measured included the total number of seeds, thousands seed weight, total grain weight, ear number, spike let number and efficiency of water use in different treatments. Results show that among all treatments, except number of spikes and straw, the grain weight, grain yield, number of spike lets per spike and biological yield at 1% probability level, and seed number at 5% probability level, have significant effect compared to the incidence of drought. But all studied cultivation methods treatments did not show significant differences. They have same reactions relative to different cultivation methods. Thus differences in yield are due to water stress for different stages of growth. The main reason is the role of water stress in forming of spike lets per spike and grain weight.

In multiphase flow systems of two immiscible fluids like air and water in a porous medium, e.g. an unsaturated soil, the flow properties depend on the amount and the spatial distribution of the phases within the pore spaces. At the pore scale, the phase distribution is controlled by the capillary forces depending on the pore size, surface tension, and wettability. For that reason, the relationship between the capillary pressure and liquid saturation (Pc–Sw relationship) is of high importance for the simulation of water flow in unsaturated soils. In this regard, dynamic pore network models can play a valuable role in predicting capillary pressure-saturation relationship. In the present study, numerical results from a dynamic pore network model which represents the void spaces of an unsaturated soil by a lattice of pores connected by throats are used to determine macroscopic relationships between capillary pressure and fluid saturations. Then using the resulted relationships from the pore network modeling and solving the partial differential Richard's equation using finite difference scheme, wetting patterns of drip irrigation have been simulated. Also, soil wetting patterns resulted from drip irrigation were investigated in laboratory experiments in a sandy soil with three dripper discharges rates of 2, 4 and 6 L.h-1 and different time intervals of 20, 40,… and 360 min. The performance of pore network model was evaluated by comparing the simulated wetting patterns with those of observed and simulated by HUDRUS software package. The results of current research showed that the pore network model for each of above-mentioned discharge rates had higher precision in comparison to HYDRUS model estimates of wetted pattern’s depth. With the exception of discharge rate of 2 L.h1, observed trend has been similar for estimation of wetted pattern’s radius and pore network model showed less error in comparison to HYDRUS model in estimation of wetted pattern’s radius.

Water use management could have a significant role in a suitable 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 citrus gardens were evaluated. The gardens located in Fasa city of Fars province, and the irrigation systems were in theform of trickle irrigation system. Irrigation waters were scheduled using tensiometer, infrared thermometer, soil moisture meter and the national water requirement document. The irrigation water applied by the gardeners was also measured. Economical analysis was also performed. Results showed that the irrigation scheduling toolsreduce the gardener applied irrigation water about 49 and 57% in the two gardens. The garden yields were not affected by the irrigation scheduling treatments. The water productivity increased about 120 and 140%, comparing to the gardener treatment. The suitable irrigation management tools in the garden with medium soil texture were tensiometer and the national water requirement document, while in the garden with coarse soil texture, were the national water requirement document and the soil moisture meter.

Due to the current conditions on the arid and semiarid climates such as the lack of rainfall and high evaporation rate, the correct and efficient management of available water resources is inevitable. Management of groundwater resources as the most frequently used source of exploitable water is one the necessities of modern research. In this study, using quantitative data observation wells and meteorological parameters of Ramhormozplain in Khuzestan province during the 7-years period, performance of the Gamma Test evaluated and compare the accuracy of least squares support vector machine (LS-SVM) and artificial neural network (ANN) models to estimate water-table was discussed. Initially, using the Gamma Test among the parameters affecting the water table, input parameters for groundwater table estimation modeling of 127 certain combinations was optimized. The 5 better combinations with the least amount of Gamma Statistic than other combinations were obtained. Then, optimal combinations were evaluated using least squares support vector machine with different kernel functions and artificial neural network. Results of 4 combination showed accurate performance of LS-SVMRBF model that the optimal combination of LSSVM model with RBF kernel function has parameters of RBF function (2=4.99) and performance parameters such as (R2=0.999, RMSE=0.3401) than ANN model was and also represents the gamma test was optimized processing.

Sediment control is one of the most important issues in hydraulic structures designing. Many attempts have been carried out to reduce the amount of sediment entrance to the intakes. The amount of delivered sediment into the lateral intake depends mainly on the flow pattern in the head of the intake. Therefore, changing the main channel wall slope may change the flow pattern and consequently amount of delivered sediment into the intake. In this experimental study, in order to investigate the effect of inclined main channel wall on the amount of delivered sediment into the lateral intake, a series of experiments were carried out for both vertical and inclined (z=1.5) main channel wall. Also, the effect of submerged vanes in the both channel wall types, was studied. Dimensional relations and variables were developed using non-dimensional analysis. Results showed that inclining the main channel wall causes decreasing bed load sediment entrance into the lateral intake. Furtheremore, submerged vanes in both vertical and inclined main channel wall decrease sediment entrance into the lateral intake but reduction of sediment entrance in inclined wall especially in low diversion ratio is more than the vertical wall. For example, in the case of inclined wall with submerged vanes for 12% diversion ratio, 100% of sediment reduction was obtained compared to the vertical wall.

The great challenge of the agricultural sector in countries located in arid and semiarid regions in the face of inadequate quantity and quality of water, Produce more food with less water or agricultural production is optimized. Such methods can be used to optimize agricultural production, water-salinity production functions named that Planning and policy for agricultural production in this area is useful. To determine the crop water production function water-salinity, this experiment was carried out at 2011 in Khorasan Razavi provience. Maize was grown with three levels of saline water (1.8, 3 and 4.6 dS/m), four levels of applied water (100, 75, 50 and 25 percent of water requirement) and four levels of stage of deficit irrigation applied (continuously during the growing season, vegetative, flowering and grain filling). Data were analyzed using linear, quadratic, Cobb-Douglas and transcendental functions. Results showed that quadratic function estimated yield better under salinity and water stress. Marginal rate of technical substitution showed that water salinity and water supply can be substituted with the other in a wide range in order to achieve equal amount of yield. Marginal production of water quantity and quality were 0.77 and -2.75 ton.ha-1, respectively.

Climate variability is the most effective parameter on crop productivity especially rainfed crops.in this study, the anomaly index was calculated for meteorological elements such as maximum temperature(T max), minimum temperature(T min), precipitation(P) and crop yield(Y) for Razavi Khorasan province in Iran, which is located in arid and semi arid region of the world. Precipitation Anomaly Percentage (PAP) is a traditional drought monitoring index, it shows the precipitation as a percentage of the long-term average or normal Thepurpose of this study is finding significant relation between various indexes such as yearly precipitation anomaly (PA) with yearly maximum temperature anomaly(T max A) and yearly minimum temperature anomaly(T min A) for the period (1989-2005).At first, moving average of 5, years old,were examined for 10 stations. In addition, yearly precipitation anomaly, probability and return period of it were calculated using sigmoidfunction. Pearson correlation was examined to find relationship between change percent of yearly precipitation anomaly(PAP), yearly minimum(TminAP), maximum temperature anomaly(TmaxAP) and yearly rainfed crop yield anomaly of wheat (YAP). Multiple linear regression was calculate between YAP (as dependent parameter) and climate variability(indpendent parameter). Sarakhs, Ghuchan and Mashhad had significant correlation (P <0.05) 0.63,0.55 and 0.54 respectively. In other station, no relation found between PAP and YAP. A significant relation between TmaxAP and YAP was obtained in Mashhad (P < 0.05, r= -0.48) and TminAP and YAP was found only in Ghuchan(r=0.56).

Some studies that investigate the climate change and hydrologic balance relationships utilize reference evapotranspiration to either calculate the changes in trends and magnitude of actual ET or to determine changes in atmospheric demand. Some studies utilize temperature or radiation-based empirical equation. Since many climate variables that affect ETo rates have been changing, single-variable equation for estimating the trend and magnitude of ETo should be avoided. The present and future temporal characteristics of ETo are examined in this paper. ETo are calculated during 1961-2005 by the Penman-Monteith recommended by FAO with historical weather data while ETo during 2011-2099 are downscaled from HadCM3 outputs under two emission scenarios(A2 and B2) by SDSM and under A2 by LARS-WG. Results showed that Downscaled ETo by SDSM will increasing during 2011-2099 at a Rate of 1.7 and 0.96 mmyr-1 under A2 and B2 scenario respectively. Averaged over the two emission scenarios, the projected increase of downscaled ETo by SDSM are 4.2%, 7.1% and 12.5% for the three periods 2020s, 2050s and 2080s respectively. Another model has projected 3.4%, 7.8% and 14.9% increases in ETo for these three periods respectively.

Droughts, Floods, and extremes of meteorological parameters are among the cases which may happen due to climate change. This phenomenon highly affects agricultural products. Therefore, analysis of effective rainfall is one of the important sources of soil moisture. Therefore, analysis of effective rainfall in planning of dry farming is essential. In this study two downscale models (ASD and LARS-WG5) were used for prediction of changes in effective rainfall. The models were run for 3 future periods of 30 years in 19 synoptic stations which are located in different climatic zones of Iran. The results showed that effective rainfall in Zahedan station will increase 2.35, 2.32, and 2.31 times in next future 30 years periods. These values for Yazd are 3.1,3.0 and 3.0, respectively.