Submitted to: Proceedings of the International Salinity Forum
Publication Type: Proceedings
Publication Acceptance Date: April 11, 2005
Publication Date: April 25, 2005
Repository URL: http://www.ars.usda.gov/SP2UserFiles/Place/53102000/pdf_pubs/P2078.pdf
Citation: Suarez, D.L. 2005. Unsatchem 3.1: computer model for prediction of water and mulitcomponent solute transport. In: Proceedings of the International Salinity Forum, Managing Saline Soils and Water: Science, Technology, and Soil Issues. April 25-27, 2005. Riverside, CA pp:163-168. Interpretive Summary: Limited water resources in arid regions such as the southwestern U.S. means that we must develop methods to utilize marginal waters and soils in sustainable irrigation systems. There is a need to develop computer models that applicable to field conditions to assist in site specific management. This updated computer model provides routines for use in management of high B soils and improved routines for prediction of exchangeable Na and thus sodic soil reclamation. Other improvements include prediction of potential crop water requirements and relative yield when water requirement information is not available. The model has wide applicability for use by water quality and irrigation specialists in arid regions.
Technical Abstract: The previously developed computer model UNSATCHEM has been modified and upgraded with several new and unique capabilities. The model contains capability to predict B adsorption and transport (without the need for detailed adsorption data) based on prediction of the constant capacitance constants from generally available soil properties information, a calcite kinetic precipitation model that considers the effect of dissolved organic carbon, as well as a clay- organic matter mixing model to predict cation selectivity constants. Several existing features are also unique, such as prediction of CO2 concentrations in the root zone, consideration of the effects of soil chemistry on hydraulic properties and inclusion of a kinetic model to describe calcite dissolution and precipitation. A version of the model, developed for FAO (Suarez and Vaughan, 2001), has a reduced set of options but a simpler interface suitable for users who are not modeling specialists. This model also includes calculation of ET0 using the FAO version of the Pennman Monteith equation (Allen et al., 1998), and crop coefficient information.