Modelling movement of nitrate from non-point sources in deep and heterogeneous vadose zone using hydrus 2D/3D
Student name: Mr Ankit Jain
Guide: Dr Prateek Sharma
Year of completion: 2012
Host Organisation: Civil Engineering Department, Indian Institute of Technology, New Delhi
Supervisor (Host Organisation): Dr Brijesh Kumar Yadav
Abstract: Nitrate has become a potential groundwater contaminant because of intensive application of
nitrate fertilizers and low irrigation practices. Moreover, spatial heterogeneity results in
preferential flow processes resulting in hastened transport of nitrate to deeper parts of vadose
zone. Present work is based on the modelling of movement of nitrate in a 15.8 deep vadose zone
using HYDRUS-2D/3D model. An equilibrium approach and a dual-porosity approach were
applied to the field data of San Joaquin Valley, California and their outputs were compared with
those published in the literature. Equilibrium approach largely under-predicted the leaching of
nitrate to groundwater while dual-porosity approach showed that higher leaching of nitrate takes
place which is in line with the field observed data. Several discrepancies were found between the
observed data and results from the dual-porosity simulation regarding nitrogen storage in the
vadose zone which was over-predicted by the simulation results and are attributed to the flow
occurring in the matrix and denitrification losses in the deeper vadose zone. Various modelling
approaches are suggested which may provide better results than the dual-porosity approach. It
was found that nitrate leaching was about 10 times higher in the subplot with higher nitrate
application rates as compared with standard subplot and hence it is suggested that proper
irrigation and fertilization application are necessary to prevent groundwater contamination by
leaching of fertilizer.
Keywords: Nitrate, HYDRUS-2D/3D, Preferential flow, Heterogeneous vadose zone, Dualporosity
approach
