H Nozari - Department of Irrigation and Reclamation Engineering, University of Tehran, Iran
A Liaghat - Department of Irrigation and Reclamation Engineering, University of Tehran, Iran
M Kholghi - Department of Irrigation and Reclamation Engineering, University of Tehran, Iran

The quantity and quality of drain water in saline soil is changing from operation of irrigation and drainage network to a balance status. It will take a very long time, maybe several years, to reach a balance status. Therefore it is very important to have this kind of knowledge to management and control of drain water, during these times. In this paper, the system dynamics technique was used to simulate the performance of a drainage system in unsteady state condition. In fact the system dynamics technique is one of the object oriented approaches that studies and manages complex feedback systems. The model is capable to predict many hydrological parameters such as water table fluctuation, drainage discharge, drain water salinity and ground water salinity. All above parameters were investigated theoretically and their trends were found to be legible. The model was validated using data collected at a tile drained experimental site irrigated with shallow ground water located at khouzestan, Iran. The results indicated the good agreement between the observed and simulated parameters.

System Dynamics, Unsteady State, Drainage System, Hydrological Parameters, Quantity and Quality of Drain Water