The impact of phosphorus inputs from small discharges on designated freshwater sites.

Published online
21 Jan 2021
Published by
Natural England
Content type

May, L. & Place, C. & O'Malley, M. & Spears, B.

Publication language
European Union & Europe


This report aims to provide an indication of the potential scale and nature of the problem of small discharges ofphosphorus (P) for designated sites and to start the process of identifying management solutions to reduce impacts, where required. This will be used to determine the possible scale of such discharges as a factor influencing the condition of designated freshwater SSSls (Sites of Special Scientific Interest) more generally and to raise awareness of the issue. It will also be used to inform and influence site management strategies and to identify research needs and advice for future improvement programmes (e.g. Water Framework Directive Programme of Measures; water company asset management plan process). The scope of this work is limited to the impact of P on freshwater habitats. The study is divided into two main tasks. Task 1 reviews appropriate literature concerning the impact of small discharges of P in relation to eutrophication; reviews existing guidance on managing small discharges; summarises the conditions under which small discharges may result in significant impacts at local and/or site level; describes the range of options available to deal with small discharges; and suggests an approach that could be applied across aquatic SSSIs to establish the scale and likely impacts of small discharges. Task 2 undertakes two desk-based case studies to investigate the scale and potential impact of both consented and unconsented small discharges on water quality; and develops an outline risk assessment process for prioritising remediation measures.

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