Field-scale modeling to explore salinity problems in irrigated agriculture

One-third of irrigated land is affected by salinity or is expected to become so in the near future. A rapid assessment to evaluate the effect of changes in the quality and quantity of irrigation water was tested for the Rudasht irrigation project in Iran. This was performed by using a physically based, well-tested simulation model for crop growth, water and salt transport at field scale. Data used were from an existing dataset and missing data were obtained by converting data from the available set to the required ones. Results indicate that the current practice of 900 mm annual application rates 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 water and salt balances. It was concluded that the methodology presented here is versatile, rapid, and transferable to other conditions. Moreover, the method produces output at a high spatial and temporal resolution over a long time frame. Copyright (C) 2001 John Wiley & Sons, Ltd.