This text contains selected and reviewed papers of the second Workshop on Crop-Water-Models held in 1993 on the occasion of the 15th Congress of the International Commission on Irrigation and Drainage (ICID) in The Hague, The Netherlands. The models included in this work meet the following criteria: i) the models have been calibrated and validated against field data and ii) the models are operational, ie. users have access to and may rely on existing software for model implementation. The papers included in this volume cover a wide range of modelling objectives, approaches and applications. The first group of models places primary emphasis on irrigation scheduling. Crop-water relations are described by simple, yet sound, simulations of the soil water balance and yield-water use relations. Their application to field practice is generally straightforward, since the basic parameters required to describe the soil-plant-atmosphere relationships are available. The second group of models aims at a more detailed description of soil water fluxes, and a more sophisticated approach to crop growth and yield formation is taken. Thus, these models may require more complex inputs; characterizing soil hydraulic properties, plant physiology and climatological parameters. Their usage in practice should be restricted to users who have a good understanding of processes in the soil-plant-atmosphere continuum. The last group of models concerns those which can be applied on a large scale, particularly to the design or management of irrigation systems. In general, this last group aims at forecasting or computing aggregated irrigation water demands for an irrigation sector, scheme or system level. The aggregation of demands from a small scale to a larger scale varies from simplified algorithms to the use of GIS. This book should be of use to researchers, engineers and managers involved in the modelling and practice of crop-water irrigation and agricultural water management.