Knowledge of crop response to different moisture conditions is essential for analysing water allocation problems at the farm level. Inadequate experimental data and the time and cost involved in obtaining sufficient data for adequate estimations of yield-water relationships are probably the major bottlenecks in developing countries. One approach to this problem is to transfer water production function knowledge from advanced countries, where several specific forms of water production function models have been developed. It is not possible to transfer empirical production function models because they are site specific, but, among the synthetic partial crop-water response models, those that relate yield to evapotranspiration are transferable to developing countries. Simulation and physiological models are more realistic than partial models, that require a large amount of data.