CATCHCROP: Modeling crop yield and water demand for integrated catchment assessment in Northern Thailand

As part of an Integrated Water Resource Assessment and Management project (IWRAM) in Northern Thailand, a Decision Support System is being constructed in order to provide guidelines for crop diversification and water allocation. The IWRAM software integrates a crop model with hydrological and economic models. Presented here is the integrated crop model, called CATCHCROP, which is capable of simulating yield response to water deficit and fertility depletion. External and internal constraints have largely influenced the model construction. Paucity of observed data and its reliability required the use of conceptual and recognized algorithms. Linkages with the economic and hydrological models led to the choice of a 10-days time step. The stand-alone version of the model has been tested against available data sets coming from two small catchments. First results are fairly satisfactory but it is acknowledged that this kind of integrated model should not be used at the farm plot level to assess cropping practices.