فصلنامه حفاظت منابع آب و خاک
سال پنجم شماره 1 (پیاپی 17، پاییز 1394)

Stochastic characteristics of the drainage phenomena led to the application of random variables and time series modeling in predicting the performance of these phenomena. The aim of this study was to investigate the potential of time-series models in predicting the performance of a subsurface drainage system. Behshahr Ran subsurface drainage system, which its drains are activated via rainfall, was considered as the study area. In this study, Drainmod model was calibrated for the study area. Then, variables of drainage discharge and water table depth were simulated via the calibrated Drainmod model. This information was used to evaluate the performance of various time-series models. The results showed that the ARMAX model with exogenous variables including daily value, precipitation during the previous days and average desired variables in the last two days was efficient in estimating water table depth and drainage discharge. Mean absolute error for predicting both variables was about 8%. Comparison between the selected times series models and the calibrated Drainmod model results indicated the application of time-series models in predicting the performance of the subsurface drainage system was satisfactory. The coefficients of determination were 0.51 and 0.74 for drainage discharge and water table depth, respectively. The root mean squared error for these variables were 0.01 cm/day and 8.6 cm, respectively.

Water resource management is a main driver to increase economic productivity for an agricultural area. Under water shortage condition, efficient use of available water is necessary for required sustainable crop production in arid and semi-arid area. Therefore, a combination procedure of mathematical modeling and optimization techniques has been developed for water allocation to maximize the economical productivity and total efficiency of an irrigation scheme.Optimization model is presented using multiobjective genetic algorithm and evaluate by two objective functions. Water use efficiency, cropping pattern, reduction of irrigation losses, effective use of rainfall and cultivated area are considered in the objective functions of the model. Irrigation water requirement for each growing stage and cultivated area have been considered as decision making variables. For field study, the main crops of Baghmalek plain and their related area, the cost of agricultural inputs and final price of crops were collected in farming year 2013-2014. The results show that the optimal cultivation area allocated among various crops is decreased for maize, melon, tomato and onion in drought condition. Tomato, bean and onion have obtained more volume of total available water, respectively. Tomato in relative yield and net benefit ratio, vegetable in the percentage of allocated water and bean in effective use of water have the minimum values of evaluation parameters.

Measurement of soil moisture characteristic curve in laboratory and field is costly, time consuming and difficult. Since, this curve is necessary for studying water movement in unsaturated soil, therefore using the estimated methods for this curve is common. The model of Grykson et al. (1987) is a single one parameter model based on the logarithmic shape. This model has two coefficients with negative correlation and the other unknown parameter. In this study, soil bulk density and geometric standard deviation of the particle-size diameter were used for determining the unknown parameter of model. For this purpose, 160 soils from UNSODA soil data bases and 32 soils from Fars province were used, and four conditions have been considered: a) Calibration the results for different soil textural classes and validation the results for remained soils in each soil textural class. b) Calibration the results for UNSODA soils and validation the results for soils of Fars province. c) Calibration the results for soils of Fars province and validation the results for UNSODA soils. d) Calibration the results for about 80 percent of total soils and validation the results for about remained 20 percent of soils. The obtained results in condition one showed the good accuracy for estimating soil moisture characteristic curve in different soil textural classes. Also, the comparison of conditions two, three and four indicated that the calibration results based on UNSODA soil data bases were better for estimating soil moisture characteristic curve.

Access to irrigation scheduling and water and nitrogen management effects on growth of eggplant, because it When can increase the yield of the proper management of water and fertilizer is needed. The present study was undertaken to investigate the possibility of reducing water consumption at eggplant plants using drip irrigation tape (Tape) and Appropriate amount of nitrogen fertilizer and its effect on crop yield and the production function and Crop coefficient (Kc) and Crop drought resistance factor (Ky), in a randomized complete block design with three replications in the city of Astaneh Ashrafiyeh in 2010 crop year. Main plots consisted of non-irrigated (dryland) and drip irrigation management, 60, 80 and 100% of crop water requirement and two minor amounts of nitrogen including zero, 90, 120 and 150 kg.N.ha-1 were applied. The results showed that Drip irrigation at 100% of crop water management with the application of 120 kg.N.ha-1 produced maximum yield was with 51.9 ton.ha-1. WUE values varied in the range of 4.20 to 11.42 kg/m3 in relation to nitrogen management and irrigation had a greater effect on yield. Crop coefficient obtained during the growing season varies for Eggplant was between 0.8 to 0.9 while resistance factor was Ky =1.06. The results showed that there were significant differences in plant height and length of the roots in irrigation management, and content management across the product nitrogen. But yield, number of leaves, length and width of the product and water use efficiency of eggplant were affected by the amount of irrigation water and fertilizer and their interactions.

Water and organic contaminant transport in soil porous media, particularly in light textured soils due to high transmission capacity and create a secondary sources of pollution is very important. The aim of this study was kerosene and water transport in a light texture soil system containing different treatments of montmorillonite nanoclay. For this purpose, treatments including 0, 2, 4 and 6 wt% of nano clay- sandy soil in a funnel containing filter paper based system was applied. Then kerosene and water (4 pore volumes alternatively) were passed into soils. The breakthrough curves showed that the water passes through soils was slower and gentler slope, so the volume output was lower compared to kerosene. It seems that water molecules with a diameter of less than 3.0 nm fitted well in the small spaces between the layer of nanoclay, which are held with strong hydrogen bonds. Kerosene, with a density equals 0.78, only attract surface places, therefore, pass from porous soil surface well due to having molecules with 11 to 15 carbon atoms, which are larger than the density of water. In both fluids, the more percentage of nanoclay there is, the more retention of kerosene and water would be expected. The results of X-ray showed that the distance of nanoclay increased from 14.4 to 24.77 Å with addition of water.

In the present study first the agricultural production functions was estimated based on three techniques of full irrigation and deficit irrigation 5 and 10 percent in order to presentation of the practical solution to conservation of surface and underground water resources in Qazvin plain. The optimal amounts of cropping pattern were determined in Qazvin province by a non-linear programming model. Then, the effects of deficit irrigation was investigated on cropping pattern, water used and farmer’s gross marginal simultaneously with reduced available water under scenarios 10, 20, 30 and 40 percent. To estimating of the agricultural production functions was used Ordinary Least Squares method and Eviews software. The non-linear programming model was solved in GAMS software. The results of estimated production functions showed that deficit irrigation 5 percent creates a slight decrease in products yield. But, deficit irrigation 10 percent has the negative effect on yield of most products. The results of non-linear programming model showed although use of deficit irrigation 5 percent simultaneously with reduced available water policy creates the slight decrease in farmer’s gross marginal but this technique helps to maintain and sustainability of surface and underground water resources of Qazvin plain strongly.