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dc.contributor.authorWilson, Scott
dc.contributor.authorClose, M. E.
dc.contributor.authorAbraham, P.
dc.date.accessioned2018-02-02T02:51:58Z
dc.date.available2017-11-26en
dc.date.issued2018-01
dc.date.submitted2017-11-23en
dc.identifier.issn0022-1694en
dc.identifier.urihttps://hdl.handle.net/10182/8996
dc.description.abstractDiffuse nitrate losses from agricultural land pollute groundwater resources worldwide, but can be attenuated under reducing subsurface conditions. In New Zealand, the ability to predict where groundwater denitrification occurs is important for understanding the linkage between land use and discharges of nitrate-bearing groundwater to streams. This study assesses the application of linear discriminant analysis (LDA) for predicting groundwater redox status for Southland, a major dairy farming region in New Zealand. Data cases were developed by assigning a redox status to samples derived from a regional groundwater quality database. Pre-existing regional-scale geospatial databases were used as training variables for the discriminant functions. The predictive accuracy of the discriminant functions was slightly improved by optimising the thresholds between sample depth classes. The models predict 23% of the region as being reducing at shallow depths (<15 m), and 37% at medium depths (15-75 m). Predictions were made at a sub-regional level to determine whether improvements could be made with discriminant functions trained by local data. The results indicated that any gains in predictive success were offset by loss of confidence in the predictions due to the reduction in the number of samples used. The regional scale model predictions indicate that subsurface reducing conditions predominate at low elevations on the coastal plains where poorly drained soils are widespread. Additional indicators for subsurface denitrification are a high carbon content of the soil, a shallow water table, and low-permeability clastic sediments. The coastal plains are an area of widespread groundwater discharge, and the soil and hydrology characteristics require the land to be artificially drained to render the land suitable for farming. For the improvement of water quality in coastal areas, it is therefore important that land and water management efforts focus on understanding hydrological bypassing that may occur via artificial drainage systems.en
dc.format.extent611-624en
dc.language.isoen
dc.publisherElsevier
dc.relationThe original publication is available from - Elsevier - https://doi.org/10.1016/j.jhydrol.2017.11.045en
dc.relation.urihttps://doi.org/10.1016/j.jhydrol.2017.11.045en
dc.rights© 2017 Elsevier B.V. All rights reserved.
dc.subjectnitrateen
dc.subjectredox statusen
dc.subjectstatistical modellingen
dc.subjectNew Zealanden
dc.subjectEnvironmental Engineeringen
dc.titleApplying linear discriminant analysis to predict groundwater redox conditions conducive to denitrificationen
dc.typeJournal Article
lu.contributor.unitLincoln University
lu.contributor.unitLincoln Agritech
dc.identifier.doi10.1016/j.jhydrol.2017.11.045en
dc.subject.anzsrc040603 Hydrogeologyen
dc.subject.anzsrc079901 Agricultural Hydrology (Drainage, Flooding, Irrigation, Quality, etc.)en
dc.relation.isPartOfJournal of Hydrologyen
pubs.organisational-group/LU
pubs.organisational-group/LU/Lincoln Agritech
pubs.organisational-group/LU/Research Management Office
pubs.organisational-group/LU/Research Management Office/QE18
pubs.publication-statusPublisheden
pubs.volume556en
dc.identifier.eissn1879-2707en
lu.identifier.orcid0000-0002-9212-2026


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