Decision support model for irrigation water management

A software package called Command Area Decision Support Model (CADSM) was developed to estimate aggregate crop-water requirements and to study management options for irrigated areas. Daily water and salt balances are simulated for individual fields within command areas based on crop type and stage of development, field characteristics, soil properties, possible ground-water contribution, salinity level, and several queuing factors that take cultural practices into account. The water requirements for individual fields are aggregated to estimate the potential command area water requirement, then totaled to determine the potential irrigation system demand. A queuing system is used to allocate available water to command areas and fields. Average crop yield response is predicted considering root-zone water deficit, salinity concentration, and water logging. Daily weather data, including evaporation, air temperature, and reference crop evapotranspiration (ET(o)) can be generated using monthly statistical means and standard deviations. Model verification and calibration studies were conducted using various climatological data, cropping patterns, and simulated field conditions. Model results are shown to correlate well with measured field data from Utah and Thailand.