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Estimation of lag time of water and nitrate flow through the vadose zone: Waikato and Waipa River catchments

TR 2018/31
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Report: TR 2018/31

Author: Scott Wilson and Ali Shokri (Lincoln Agritech Ltd)

About this report

This report was commissioned by the Technical Leaders Group for the Healthy Rivers Wai Ora Project Report No. HR/TLG/2015-2016/1.3

This report presents a methodology and results for predicting the time taken for nitrate to travel from the land surface, though the unsaturated (vadose) zone and into shallow groundwater.

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Estimation of lag time of water and nitrate flow through the vadose zone: Waikato and Waipa River catchments [PDF, 12 MB]

Contents
1 Introduction
1.1 Study objectives
1.2 Scope and nature of the services
1.3 Introduction to time lags
1.4 Conceptual model
2 Soil moisture balance model
2.1 Methodology
2.2 Model inputs
2.2.1 Soil data
2.3 Model modifications
2.3.1 Runoff
2.3.2 Readily available water
2.3.3 Interception
2.4 Soil moisture balance results
3 Unsaturated zone model
3.1 Theoretical background
3.2 Unsaturated zone methodology
3.2.1 Assumptions
3.2.2 Numerical procedure
3.3 Vadose zone model parameterisation
3.3.1 Static water levels
3.3.2 Hydraulic properties
3.4 Vadose zone model results
4 Saturated zone model
4.1 Saturated zone model methodology
5 Comparison with tritium data
6 References