Understanding the Interactions Between Soil Chemistry, Soil Hydraulic Properties and Deep Drainage.

Understanding the interactions between land and water management practices and groundwater response in some irrigated systems remains an ongoing challenge. This is due in part to the dynamic and complex interactions between the chemistry and physics of the unsaturated zone, and the ‘conflict’ between needing to retain nitrate within the root zone while exporting salt from the root zone. In this paper we discuss application of the HYDRUS model with major ion reaction and transport and soil water chemistry-dependant hydraulic conductivity to analyse these interactions. We discuss in particular the use of gypsum as a soil ameliorant and the potential impacts of changes in soil chemistry on soil hydraulic properties, and hence deep drainage.