Field-scale modeling to explore salinity problems in irrigated agriculture

One-third of irrigated land is affected by salinity or is expected to becom e so in the near future. A rapid assessment to evaluate the effect of chang es in the quality and quantity of irrigation water was tested for the Rudas ht irrigation project in Iran. This was performed by using a physically bas ed, well-tested simulation model for crop growth, water and salt transport at field scale. Data used were from an existing dataset and missing data we re obtained by converting data from the available set to the required ones. Results indicate that the current practice of 900 mm annual application ra tes for cotton, given the current salinity level of 4 dS m(-1), is close to the optimal one. Graphs are presented to evaluate the effect of different combinations of application rates and salinity levels on yields, and the wa ter and salt balances. It was concluded that the methodology presented here is versatile, rapid, and transferable to other conditions. Moreover, the m ethod produces output at a high spatial and temporal resolution over a long time frame. Copyright (C) 2001 John Wiley & Sons, Ltd.