High flows contributed a large part of annual contaminant yields in New Zealand’s rivers
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Meenken, E
Noble, A
Kittridge, M
Ausseil, O
Keenan, L
Snelder, T
Doscher, C
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Abstract
Accurate contaminant yield estimation in rivers is essential to developing water quality policies and monitoring their effectiveness over time. We assessed the contribution of high-flows (≥90th percentile) to total yields of nitrate-nitrogen, total nitrogen, total phosphorus, and E. coli calculated from monthly data over 15 years (310–325 sites) in New Zealand, and at 24 sites with high-frequency (30-min) nitrate-nitrogen and total phosphorus. High flows contributed 51–74% of annual contaminant yields at long-term sites and 48% of nitrate-nitrogen and 63% of total phosphorus in the high-frequency sites. Mean uncertainties in annual yields estimated from monthly monitoring data (compared to the true yield, calculated from high-frequency records) were 29% for nitrate-nitrogen and 52% for total phosphorus. Daily sampling was needed to reduce uncertainty to <10% especially in catchments with a high proportion of agricultural land use.
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Communications Earth & Environment
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6
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© The Author(s) 2025. Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
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McDowell, RW; Meenken, E; Noble, A; Kittridge, M; Ausseil, O; Keenan, L; Snelder, T; Doscher, C, High flows contributed a large part of annual contaminant yields in New Zealand’s rivers, Communications Earth & Environment, 2025, 6, pp. 335