ارزيابي مزرعه اي روابط زهكشي در شرايط غير همروان در منطقه شمال شرق

Field Evaluation of some Applied Unnteady state Drainage Equation at North East Ahwaz

Irrigated land in area such Iran, usually requires subsurface drainage for the removal of excess water and dissolved salts from the root zone. Calculation of drain spacing is based on theoretical relationships. In practice these theoretical equations fail at field conditions. This is due to some in herent assumptions which made during derivatign of the equations. Therefore theoretical relationships have to be tested and evaluated under field conditions. Results obtained from such evaluations and experiments lead to more reliable design of drainage system under similar soil and climatic condition. The purpose of this investigation was the selection of most suitable drainage spacing design formulas in the northeastern region of Ahvaz representing a relatively large agricultural development region. Necessary data like depth of irrigation water, water table fluctuation, soil hydraulic conductivity etc. were regularly collected for a 130 day period starting Jan I, 2000, on a 50 ha experimental site belonging to Ramin Experimental site of Shahid Chamran University. The collected data were used to calculate drain spaces by solving unsteady state drainage equations. The resulted data were then campaired with actual data. The results showed that the Dumm Equation gives the best predication for 60m and 80m drain spacing in comparison to actual data.