Does land use affect pathogen presence in New Zealand drinking water supplies?

Phiri, Bernard J., Pita, Anthony B., Hayman, David T.S., Biggs, Patrick J., Davis, Meredith T., Fayaz, Ahmed, Canning, Adam D., French, Nigel P., and Death, Russell G. (2020) Does land use affect pathogen presence in New Zealand drinking water supplies? Water Research, 185. 116229.

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Four microbes (Campylobacter spp., Escherichia coli, Cryptosporidium spp. and Giardia spp.) were moni- tored in 16 waterways that supply public drinking water for 13 New Zealand towns and cities. Over 500 samples were collected from the abstraction point at each study site every three months between 2009 and 2019. The waterways represent a range from small to large, free flowing to reservoir impoundments, draining catchments of entirely native vegetation to those dominated by pastoral agriculture. We used machine learning algorithms to explore the relative contribution of land use, catchment geology, vegeta- tion, topography, and water quality characteristics of the catchment to determining the abundance and/or presence of each microbe. Sites on rivers draining predominantly agricultural catchments, the Waikato River, Oroua River and Waiorohi Stream had all four microbes present, often in high numbers, through- out the sampling interval. Other sites, such as the Hutt River and Big Huia Creek in Wellington which drain catchments of native vegetation, never had pathogenic microbes detected, or unsafe levels of E. coli . Boosted Regression Tree models could predict abundances and presence/absence of all four microbes with good precision using a wide range of potential environmental predictors covering land use, geology, vegetation, topography, and nutrient concentrations. Models were more accurate for protozoa than bacte- ria but did not differ markedly in their ability to predict abundance or presence/absence. Environmental drivers of microbe abundance or presence/absence also differed depending on whether the microbe was protozoan or bacterial. Protozoa were more prevalent in waterways with lower water quality, higher num- bers of ruminants in the catchment, and in September and December. Bacteria were more abundant with higher rainfall, saturated soils, and catchments with greater than 35% of the land in agriculture. Although modern water treatment protocols will usually remove many pathogens from drinking water, several re- cent outbreaks of waterborne disease due to treatment failures, have highlighted the need to manage water supplies on multiple fronts. This research has identified potential catchment level variables, and thresholds, that could be better managed to reduce the potential for pathogens to enter drinking water supplies.

Item ID: 64184
Item Type: Article (Research - C1)
ISSN: 1879-2448
Copyright Information: © 2020 Elsevier Ltd. All rights reserved.
Funders: New Zealand Ministry of Health (NZMH), Royal Society Te Aparangi Rutherford (RDF)
Projects and Grants: NZMH (contract number: 167489 / 355766/01), RDF Discovery Fellowship (RDF-MAU1701, DTSH)
Date Deposited: 01 Sep 2020 22:51
FoR Codes: 41 ENVIRONMENTAL SCIENCES > 4199 Other environmental sciences > 419999 Other environmental sciences not elsewhere classified @ 33%
41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410402 Environmental assessment and monitoring @ 33%
42 HEALTH SCIENCES > 4202 Epidemiology > 420203 Environmental epidemiology @ 34%
SEO Codes: 96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960406 Control of Pests, Diseases and Exotic Species in Fresh, Ground and Surface Water Environments @ 33%
96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960506 Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments @ 33%
92 HEALTH > 9204 Public Health (excl. Specific Population Health) > 920405 Environmental Health @ 34%
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