Sediment and nutrient retention in ponds on an agricultural stream: evaluating effectiveness for diffuse pollution mitigation

Robotham, John; Old, Gareth ORCID: https://orcid.org/0000-0002-4713-1070; Rameshwaran, Ponnambalam ORCID: https://orcid.org/0000-0002-8972-953X; Sear, David; Gasca-Tucker, David; Bishop, James; Old, Joanne; McKnight, David. 2021 Sediment and nutrient retention in ponds on an agricultural stream: evaluating effectiveness for diffuse pollution mitigation [in special issue: Mitigating the impacts of agricultural water pollution on river ecology] Water, 13 (12), 1640. 27, pp. https://doi.org/10.3390/w13121640

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Official URL: http://dx.doi.org/10.3390/w13121640

Abstract/Summary

The creation of ponds and wetlands has the potential to alleviate stream water quality impairment in catchments affected by diffuse agricultural pollution. Understanding the hydrological and biogeochemical functioning of these features is important in determining their effectiveness at mitigating pollution. This study investigated sediment and nutrient retention in three connected (on-line) ponds on a lowland headwater stream by sampling inflowing and outflowing concentrations during base and storm flows. Sediment trapping devices were used to quantify sediment and phosphorus accumulations within ponds over approximately monthly periods. The organic matter content and particle size composition of accumulated sediment were also measured. The ponds retained dissolved nitrate, soluble reactive phosphorus and suspended solids during baseflows. During small to moderate storm events, some ponds were able to reduce peak concentrations and loads of suspended solids and phosphorus; however, during large magnitude events, resuspension of deposited sediment resulted in net loss. Ponds filtered out larger particles most effectively. Between August 2019 and March 2020, the ponds accumulated 0.306 t ha−1 sediment from the 30 ha contributing area. During this period, total sediment accumulations in ponds were estimated to equal 7.6% of the suspended flux leaving the 340 ha catchment downstream. This study demonstrates the complexity of pollutant retention dynamics in on-line ponds and highlights how their effectiveness can be influenced by the timing and magnitude of events.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.3390/w13121640
UKCEH and CEH Sections/Science Areas:	Hydro-climate Risks (Science Area 2017-)
ISSN:	2073-4441
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	water quality, natural flood management, suspended sediment, phosphorus, nitrate, organic matter, on-line ponds, constructed wetlands, particle size
NORA Subject Terms:	Ecology and Environment
Date made live:	09 Jul 2021 13:46 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/530666

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.3390/w13121640

UKCEH and CEH Sections/Science Areas:

Hydro-climate Risks (Science Area 2017-)

ISSN:

2073-4441

Additional Information. Not used in RCUK Gateway to Research.:

Open Access paper - full text available via Official URL link.

Additional Keywords:

water quality, natural flood management, suspended sediment, phosphorus, nitrate, organic matter, on-line ponds, constructed wetlands, particle size