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THE USE OF PONDS TO REDUCE POLLUTION FROM
POTENTIALLY CONTAMINATED STEADING RUN-OFF
KV Heal 1 , AJA Vinten 2 , F Gouriveau 1 , J Zhang 1 , M Windsor 1 , B D’Arcy 3 , A Frost 4 ,
L Gairns 5 and SJ Langan 2
1
The University of Edinburgh, School of GeoSciences, Crew Building, West Mains
Road, Edinburgh, EH9 3JN, UK, E-mail: k.heal@ed.ac.uk; 2
The Macaulay Institute,
Craigiebuckler, Aberdeen, AB15 8QH, UK; 3 SEPA, 7 Whitefriars Crescent, Perth, PH2
0PA, UK; 4 Soil and Water Scotland, 4 Bayswell Road, Dunbar, EH42 1AB, UK; 5 SEPA,
Heriot Watt Research Park, Avenue North, Riccarton, Edinburgh, EH14 4AP, UK
SUMMARY
Ponds/wetlands are being increasingly encouraged as a tool for reducing diffuse
pollution from farm steadings in Scotland to comply with the EC Water Framework
Directive. However, guidance on their design and maintenance is limited and
their effectiveness for different farm types in Scotland is not known. Results from
continuous flow and water quality monitoring (May–July 2005) of a mature onstream
pond/wetland, constructed on a dairy farm prior to current best practice guidelines,
and from vegetation and macroinvertebrate surveys of this and two other farm ponds/
wetlands highlight some aspects to be considered in monitoring the performance of
these systems. Future work will focus on testing and improving design guidance
by systematically monitoring and modelling flow, water quality, habitat and factors
affecting performance and maintenance in representative farm ponds/wetlands,
including new systems constructed with funding from the Scottish Executive and
SEPA’s Diffuse Pollution and Habitat Enhancement Initiatives.
INTRODUCTION
The EC Water Framework Directive (WFD) (EC, 2000) requires the introduction of
co-ordinated programmes of measures to achieve good ecological status in surface
waters. The control of diffuse, land-based sources of pollution to these waters is of
increasing concern to regulatory agencies seeking to implement the Directive. In
Scotland, nutrients [nitrogen (N) and phosphorus (P)], suspended solids (SS) and
faecal indicator organisms (FIOs) arising from diffuse agricultural run-off are a major
cause of downgrading of rivers, lakes and coastal bathing waters. The use of farm
ponds to mitigate the collectively significant pollution arising from steadings has
recently been promoted in Scotland. The aim of installing ponds is to treat run-off
from farms, particularly from areas such as access tracks and roads, roofs, road
crossings and peripheral yards with only minor or occasional pollutant loading.
While many studies report good removal of nutrients, SS and FIOs in ponds and
constructed wetlands (e.g. Borin et al., 2001; Hunt and Poach, 2001; Dunne et al.,
2005a), it is necessary to evaluate the likely performance of farm ponds/wetlands, not
only immediately after installation, but also over time. Performance of these systems
has been shown to vary seasonally (Thorén et al., 2004; Dunne et al., 2005b), with
changing hydraulic and pollutant loadings (Fink and Mitsch, 2004) and may decrease
with increasing age as sediment accumulates and vegetation develops.
The processes involved in water treatment in farm ponds vary between pollutants. P
removal occurs mainly by sedimentation, adsorption to substrate and plant uptake
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