A GIS framework for modelling nitrogen leaching from agricultural areas in the Middle Hills, Nepal

A GIS framework for modelling nitrogen leaching from terraced agricultural systems has been developed. The framework incorporates an empirical model based on mass-balance principles and incorporates descriptions of the major chemical and biological nitrogen transformations occurring in such systems. The model operates at individual terrace scale but has been incorporated within the framework of a GIS to enable application at whole catchment scale and to derive spatially distributed information on N leaching. Increased nitrogen leaching in response to increased use of inorganic fertiliser applications might lead to downstream eutrophication problems. The framework has been developed and tested at three catchments in the Middle Hills region of Nepal. Predictions of N leaching are similar in magnitude to observed catchment chemical output fluxes. The framework can be easily modified as new process representation or new catchment scale data become available, it therefore has potential for wide-scale application in any region where land use is dominated by terraced agriculture.