J. Abbas Palangi, A. M. Akhond Ali,
Volume 12, Issue 44 (summer 2008)
Abstract
For an appropriate drip irrigation system design, a prediction of soil wetting pattern is needed for a given soil texture. The wetting pattern geometry is a key factor for emitter distance determination as well as crop type. The geometry of the wetting bulb is dependent on the parameters such as soil hydraulic properties, emitter discharge and the irrigation time. This study has been conducted in Albaji region in km 25 on the Ahvaz-Andimeshk road, in order to estimate the geometry of the wetting pattern under the point source trickle emitters in sandy soil with different discharge. The emitters were calibrated to provide 5, 10, 20, 30 and 40 liter per hour discharges. The maximum wetted soil surface and depth was measured by digging the irrigated soil. Two models were developed to predict wetted soil surface diameter and depth under a point source based on Buckingham's π theorem. The equations were calibrated by using the measured data. Then resulted scientific-empirical equations have been evaluated. Considering the maximum relative error of 14.3% and root mean square error of 3.8cm in estimation of the wetted soil surface diameter and depth, the models are recommended to estimate the geometry of the wetting bulbs with a high degree of accuracy, and can be used in designing and appropriate drip irrigation system management
J. Jalili, F. Radmanesh, A. A. Naseri, M. A. Akhond Ali, H. A. Zarei,
Volume 24, Issue 3 (Fall 2020)
Abstract
Agricultural water management studies require accurate information on actual evapotranspiration. This information must have sufficient spatial detail to allow analysis on the farm or basin level. The methods used to estimate evapotranspiration are grouped into two main groups, which include direct methods and indirect or computational methods. Basics of the indirect methods are based on the relationship between meteorological parameters, which impedes the use of these data with a lack or impairment. On the other hand, this information is a point specific to meteorological stations, and their regional estimates are another problem of uncertainty of their own. To this end, the use of remote sensing technology can be a suitable approach to address these constraints. Real evapotranspiration can be estimated by satellite imagery that has short and long wavelengths and is estimated using surface energy equations. Examples of such algorithms include SEBAL, METRIC, SEBS. Among the above mentioned algorithms, SEBAL and SEBS have been used. Among the factors of superiority of the SEBAL and SEBS algorithms, in comparison with other remote sensing algorithms, is a satellite imagery analysis algorithm based on physical principles and uses satellite simulation and requires minimum meteorological information from ground measurements or air models.
