JWSS - Journal of Water and Soil Science

Determination of the required water for crop and irrigation programing is of major importance in the sustainable use of water resources. The national water document is the output of the ‘net irrigation required for crops’, which is presented for the optimum allocation of water resources for the demands. The Penman-Monteith-FAO method is used in the calculation. Updating the national water document is necessary to overcome its some limitations, and to provide more adaptation to the plains conditions of the country. The objective of this study was the recognition of the existing problems of the water national document and appropriate method development for implementing in the country plains. In this regard, the required water of different crop patterns was calculated using the Penman-Monteith-FAO method in the Ghazvin plain (as a dry plain), Ghazvin province, and Fomanat plain (as a wet plain), in Fomanat province, in the period of 1976-2005. The results were compared to the water national document. It was shown that annual potential evatranspiration varied between 1330 and 1587.1 mm in the Ghazvin plain, and between 743 and 809 mm in the Fomanat plain. The calculated evapotranspiration in the present study was about 40.6% more than water national document in the Takestan station, in Ghazvin plain, as a sample station.
 

To design cost-effective and efficient drip irrigation systems, it is necessary to know the vertical and horizontal advance of the wetting front under the point source; also, the proper management of drip irrigation systems requires an awareness of the soil water distribution. Many factors influence wetting pattern dimensions, including discharge, land slope, irrigation time and soil texture. The purpose of this study was to investigate the applicability of the support vector machine in simulating the wetting pattern under trickle irrigation. After preparing a physical model made of Plexiglas with specific dimensions and filled with silty clay loam soils, experiments were conducted in the irrigation laboratory of Razi University, Iran, with emitters of 2, 4, 6 and 8 l/hour discharge during the irrigation intervals of 2 hours and 24 hours redistribution and 0,5,15 and 20% slope with three replications. In this study, the statistical indicators R², RMSE, MBE and MEF were used. R² values for the wet depth, width and area were 0.96, 0.96 and 0.92, respectively. Regarding the MBE value, the SVM model estimated the wet width and depth parameters to be 3% less than the actual value, and simulated the wet area 2.04% less than the real value. Also, according to the MEF and RMSE values, the SVM model simulated the wet area parameter with more error.  Overall, the results showed that the SVM model had a high ability to estimate the wetting pattern parameters.