The principal, over‐arching aim of any catchment management work is to improve the water quality in our freshwater ecosystems and to make a significant contribution to their attainment of good ecological status in accordance with requirements of the EU Water Framework Directive. It is therefore vital that sufficient evidence is collected to provide an objective and robust assessment of the improvements delivered. In this review we explore the data and evidence available, which, taken together, demonstrate qualitatively and quantitatively that the delivery of integrated catchment management interventions can realise genuine improvements in water quality. To support the evidence collected, we have also summarised a number of case studies which demonstrate catchment management in action.

1. 1
WATER QUALIT Y
Catchment Management Evidence Review

2. 2
Bringing people together to understand how to achieve a better
more sustainable environment
COLLABOR8 is a transnational European project, funded by the Interreg IVB North West
Europe programme, which aims to contribute to the economic prosperity, sustainability and
cultural identity of North West Europe in increasingly competitive global markets. This is
being achieved by forming and supporting new clusters in the cultural, creative, countryside,
recreation, local food and hospitality sectors using uniqueness of place as a binding force and
overcoming barriers to regional and transnational collaboration.

3. 3
“Water is the driving force in nature.”
Leonardo Da Vinci

4. 4
The Upstream Thinking Project is South West Water's flagship programme of
environmental improvements aimed at improving water quality in river
catchments in order to reduce water treatment costs. Run in collaboration with a
group of regional conservation charities, including the Westcountry Rivers Trust
and the Wildlife Trusts of Devon and Cornwall, it is one of the first programmes
in the UK to look at all the issues which can influence water quality and quantity
across entire catchments.
Published by:
Westcountry Rivers Trust
Rain Charm House, Kyl Cober Parc
Stoke Climsland
Callington
Cornwall PL17 8PH
Tel: 01579 372140
Email: info@wrt.org.uk
Web: www.wrt.org.uk
© Westcountry Rivers Trust: 2013. All rights reserved. This document may be reproduced with prior
permission of the Westcountry Rivers Trust.

5. 5
CONTENTS
Introduction 6
 Fresh water: a vital ecosystem service 6
 Pressures affecting water quality 6
 Factors that determine pollution risk 7
 The catchment management ‘toolbox’ 10
 Assessing the efficacy of interventions 15
Pollutant Summaries 16
Nutrients & algae 16
Suspended solids & turbidity 28
Pesticides 35
Microbes & parasites 45
Colour, taste & odour 52
Assessing improvements 57
Governance & planning 65

6. 6
INTRODUCTION
Fresh water: a vital ecosystem service
Rain falling on the land brings life to the plants and animals living upon it, but it also
collects and runs across the land forming rills, gullies, streams and ultimately rivers. The
transfer of fresh water onto and then across the land is one of the fundamental
processes that sustain life on Earth. All of us depend on the fresh, clean water in our
rivers and streams every day – we drink it, we bathe in it and it sustains other life on
which we depend for food and enjoyment.
Targets for the acceptable levels of pollutants in fresh water are set out in the European
Commission’s Directive on the Quality Required of Surface Water Intended for the
Abstraction of Drinking Water 1975 (75/440/EEC) and, more recently, in the European
Commission’s Water Framework Directive 2000 (2000/60/EC).
While the former EC Directive refers to the quality of raw water intended for human
consumption, the latter sets targets above which it is expected that the ecological
condition of a watercourse may be degraded.
In addition, Article 7 of the Water Framework Directive (2000) also stipulates that, for
‘waters used for the abstraction of drinking water’, waterbodies should be protected to
avoid any deterioration in water quality, such that the level of purification treatment
required in the production of drinking water is reduced.
While for most pollutants there is no inevitable link between the quality of raw and
treated drinking water, the level of contamination in raw water is directly linked to the
diversity, intensity and cost of the treatments required.
Furthermore, there are certain pollutants or physical characteristics that, when they
occur in the raw water, can severely affect the efficiency of the drinking water treatment
process. When these pressures do occur, or when the water treatment process does not
take account of a specific pollutant or group of pollutants, there can be an increased risk
that the treated drinking water may fail to reach the drinking water standards required
at the point of consumption (the tap).
Pressures affecting water quality
Aquatic ecosystems can be damaged or degraded by a wide variety of pressures, which
arise either from human activities being undertaken in specific locations (point sources)
or from the cumulative effects of many small, highly dispersed and often individually
insignificant pollution incidents (diffuse sources).
Highly localised, point sources of pollution occur when human activities result in
pollutants being discharged directly into the aquatic environment. Examples include the
release of industrial by‐products, effluent produced through the disposal of sewage, the
overflows from drainage infrastructure or accidental spillage.
Superimposed on the pressures exerted by point sources of pollution are the more
widely dispersed and less easily characterised diffuse pollution sources.
When large amounts of manure, slurry, chemical phosphorus‐containing fertilisers or
agrochemicals are applied to land, and this coincides with significant rainfall, it can lead
to run‐off or leaching from the soil and the subsequent transfer of contaminants into a
watercourse. In addition, cultivation of arable land in particular ways or the over
disturbance of soil by livestock (poaching) can make fine sediment available for
mobilisation and subsequent transfer to drains and watercourses by water running over
the surface.
Other diffuse sources include the run‐off of pollutants from farm infrastructure such as
dung heaps, slurry pits, silage clamps, feed storage areas, uncovered yards and chemical
preparation/storage areas.
Animal access to watercourses can also lead to the direct delivery of bacterial and
organic compounds to the water and to their re‐mobilisation following channel
substrate disturbance. It should be noted that, while these agricultural sources of
pollution can often appear more like point sources, they are, however, considered as
diffuse sources as they relate to widespread, land‐based, rural practices that that can
have significant cumulative effects.

7. 7
Pollutants that exert negative impacts on the quality of fresh water, degrade the health
of our aquatic ecosystems and contaminate raw drinking water are numerous and
varied. For this review, these pollutants are categorised under five main headings:
Nutrients. Phosphorus & nitrogen‐containing compounds
Suspended solids. Including both sediment & organic material in suspension
Pesticides. Including other chemical pollutants from domestic sources
Microbiological contaminants. Including faecal coliforms & cryptosporidium
Colour, taste & odour compounds. Including metals & soluble organic compounds
Factors that determine pollution risk
There are a number of factors in the landscape that determine the degree to which a
pollutant will become available in a particular location and the likelihood of it being
mobilised and carried along a pathway to a watercourse.
Soil character & condition
The characteristics and condition of the soil in a particular area both play a key role in
the ability of the land to regulate the movement of water and the likelihood that
pollutants will become available for mobilisation into adjacent aquatic environments.
Some soils, such as heavy clay‐ or peat‐based ‘stagnogleys’, are more susceptible to
damage, such as compaction, caused by intensive cultivation or livestock farming. This
increases the risk of erosion or significant surface run‐off occurring from their surface.
Other soil types, such as lighter, free‐draining ‘brown earth’ soils, can have pollutants
leached away by water passing rapidly down through them. In addition, soils with very
high levels of organic matter, such as peat, can release large quantities of organic
compounds when they are drained or their structure has become degraded.
In light of this, it is clear that careful and appropriate management of soils can be a
powerful method for minimising the risk of pollution occurring as a result of their innate
structural vulnerability.
Topography & hydrology
The shape (morphology) of the land interacts with the underlying soil type and geology
to control the movement of water across the landscape. Some of the water falling on
the land as rain will be absorbed into the soil from where it can be taken up by plants or
pass down into the groundwater held in the underlying geology.
When the soil is saturated or damaged or the underlying rock is impermeable, water
stops being absorbed and begins to move laterally across the land via surface or sub‐
surface flow. Once moving through the landscape, water then collects in rills, gullies,
drains and ditches, before entering our streams and rivers to make its way back the sea.
3
4
3
6 9
62
21
INHERENT RISK
PRACTICE
The risk that an area of land poses to
the provision of an ecosystem service,
such as the regulation of water quality,
can be conceptualised as the
interaction between the inherent
characteristics of the land and the
activities or practices being undertaken
upon it. Therefore, it is possible to
identify areas where potentially risky
practices are being undertaken and
where this coincides with a high
underlying risk that water quality could
be degraded. These high‐scoring areas
can be considered the priority for the
targeting of catchment management
interventions and also where the
greatest enhancement of ecosystem
service provision may be achieved.

8. 8
In certain areas across the landscape, where there are steep converging slopes or where
the land is flat, water will naturally accumulate more than in other areas. In these
‘hydrologically connected’ or ‘wet’ areas there is an increased likelihood, particularly
during periods of heavy rainfall, that water will run rapidly across the surface and
mobilise any pollutants that are available on the land surface.
Given the fact that certain areas, due to their morphology, have an elevated level of
hydrological connectivity and an increased probability that water will flow laterally
across their surface, it is vital that we identify them and design tailored management
interventions to mitigate any risk that they may generate pollution.
Land‐use & land‐cover
The use to which a parcel of land is put can have a significant effect on its ability to
regulate the movement of water across it and the likelihood that it will generate
pollution in the aquatic environments nearby.
Natural habitats have rougher surfaces with more complex vegetation. They therefore
have a relatively low risk of becoming a pollution source as they are more likely to slow
the movement of water across the landscape, increase infiltration into the soil and
increase the uptake of water by plants.
In contrast to natural habitats, land in agricultural production experiences greater
levels of disturbance, whether through cultivation or the actions of livestock, and there
is therefore greater risk that it will become damaged and become susceptible to
erosion, pollutant wash‐off or pollutant leaching.
While it is certainly not always the case, the risk of pollution occurring is generally higher
where land is in arable crop production or under temporary grassland. This is simply
because the presence of bare earth for longer periods and the high intensity of
cultivation undertaken on this land increases the likelihood that the soil condition may
be degraded and pollutant mobilisation may occur.
Land under permanent grassland (pasture) inherently represents a lower pollution risk
due to its undisturbed soil and more mature vegetation. However, even this landuse can
generate significant levels of pollution when its soil surface becomes damaged by high
livestock density or when large levels of nutrients or pesticides are applied to improve it.
When assessing the risk that diffuse pollution may occur, there are also areas of urban
and industrial landuse that should not be overlooked. Significant levels of pollutants
(such as sediment, oil, metals, pesticides and a variety of other chemicals) can be
mobilised from the often impermeable surfaces and drainage systems connected to
watercourses in urban environments.
In light of these differences in the ability of different land‐uses and land‐covers to
generate pollution, it is clear that either changing land‐use or ensuring that best
management practices are undertaken on each particular land‐use represent the most
important methods for the mitigation of land‐use driven pollution risk.
Hydrological assessment of a river valley

9. 9
Practice & land management
While soil characteristics, morphology, hydrology and land‐cover all contribute the
innate potential for land to generate water pollution, it is ultimately the management of
land and the practices that are undertaken upon it that will determine the likelihood and
scale of any pollution that occurs.
The intensity and timing of our activities can affect the ability of land to retain pollutants
and so increase the likelihood of pollution arising from it. The risk of pollution occurring
can be increased when land is over‐stocked with livestock in vulnerable locations or at
times of elevated risk due to the increased chance of heavy rainfall. The risk can also be
increased when land is drained, compacted with machinery or when it becomes
damaged by repeated cycles of intensive cultivation and crop production.
Furthermore, the exogenous application of additional materials (manure and slurry) and
chemicals (pesticides and fertiliser) to the land can increase the availability of pollutants
in certain areas at times when there is increased likelihood that they will be mobilised
and transported into aquatic ecosystems.
Finally, it is also important to consider the impacts that other human practices, such as
recreational and domestic activities, can have on the condition of land, the availability of
pollutants in certain areas at certain times and the risk they pose to the water quality.
+
Mapping key areas for the provision of fresh water as an ecosystem service
There are areas of land where, due to the physical characteristics of the location or a sudden change in the weather, any
land management practice, irrespective of whether it is inherently risky and despite best practice being observed, can
still result in the generation of pollution. On this high priority land, there is the greatest likelihood of water quality being
degraded and for the ecosystem services dependent on it to be compromised. In addition, these are also the areas where
the greatest environmental benefits may be realised for the minimum investment.
Through combining data on soil characteristics, landuse, land topography and hydrological connectivity we can create a
map of these innately risky and therefore the most important areas of land in a catchment (the example below shows
and analysis of this type performed on the Tamar catchment).
+
CASE STUDY
Paul Anderson

10. 10
A Catchment Management Toolbox
If we can determine which pressures are exerting negative impacts on the water quality
in our aquatic ecosystems and identify their sources in a catchment, then we can
develop a programme of tailored and targeted interventions to remove these sources
and disconnect their pollution pathways.
For many point sources of pollution, the scale of their contribution to the pollution load
in a watercourse can be characterised through monitoring and modelling approaches
and then regulatory and technological measures can be implemented to mitigate their
impacts.
In contrast to point sources of pollution, the various sources of diffuse pollution in
catchments are far harder to identify and, individually, their impacts are often too slight,
intermittent or transient to quantify with great accuracy and certainty. Despite these
challenges, however, there is now a wealth of evidence and data which do allow these
diffuse sources of pollution to be identified and for programmes of interventions and
measures to be developed to mitigate their impacts.
Over the last 10‐15 years a comprehensive suite of land management advice and on‐
farm measures has been developed to minimise loss of pollutants from farms while
maximising efficiency to increase yields and save costs. Some of the most common of
these so‐called Best Farming Practices (BFPs) that are now recommended to farmers,
and which are now being delivered on farms across the UK, are illustrated on the
following page.
There are now many organisations that have skilled, knowledgeable and highly qualified
farm advisors who are able to give advice on farming practices, including; Catchment
Sensitive Farming, Rivers Trusts, Wildlife Trusts, Soils‐for‐Profit, Natural England, the
Environment Agency and the Farming & Wildlife Advisory Group to name just a few. In
addition, land managers also obtain a considerable amount of advice from their own
agronomists and farming advisors.
What is clear is that, irrespective of who is delivering an integrated farm advice and
investment package, it should cover a broad spectrum of land management practices
and indicate where the adoption of good or best practice may minimise the risk that an
activity will have a negative impact on the environment and where it may enhance the
provision of an ecosystem service such as water quality provision.
During the development of the on‐farm intervention toolbox there were a number of
key design considerations taken into account, which allow a farm advisor to correctly
tailor and target their application:‐
Mechanism of action. It is important to understand the mechanism via which the
intervention will reduce pollution. Often this will require the presentation of evidence
that it is the farming practice that is causing pollution before intervention is
undertaken.
Applicability. Each measure must have the farming systems, regions, soils and crops
to which it can be applied clearly defined. Farm advisors must recommend
interventions that are suitable for the situation found on a particular farm.
Feasibility. The ease with which the measure can be implemented and any potential
physical or social barriers to its uptake or effectiveness must be identified. Careful
consideration must be given to measures that may impact other farming practices.
Costs & benefits. The cost of implementing, operating and maintaining the measure
must be clearly understood. The potential practical and financial benefits to the
farmer of implementing the measure must also be estimated as it is vital for
encouraging uptake of the measures. In some circumstances, where the cost is high
or the measure will result in a loss of income, the farmer or farm advisor may need to
find additional funding from incentive or capital grant schemes to enable delivery.
Strategically targeted. The measures need to be delivered into situations where
they are most likely to have the desired water quality outcome. By ensuring that the
right intervention is targeted onto the most suitable and appropriate parcel of land,
the likelihood that the most cost‐effective use of the investment has been made
increases – i.e. the greatest possible ecosystem service improvement has been
delivered for the resources deployed.

11. 11
In this review, for each of the five main pollutant categories, we give an overview of the
interventions that can been delivered to mitigate the impacts of pollution on; (1) the
ecological health of our river catchments, (2) the risks and costs incurred at drinking
water treatment works through having to treat low quality raw water, and (3) on the
generation of pollution‐derived problems in the estuaries and coastal regions in the
lower reaches of river catchments.
Furthermore, we also describe the catchment management interventions considered to
be the most effective in reducing diffuse pollution and mitigating the impacts described.
We will also attempt to evaluate and summarise the numerous studies (completed or
currently underway) which allow us to estimate the scale of benefit that these
catchment management interventions can deliver at a variety of scales.
In assessing and collating this evidence, we hope that we will be able to demonstrate
with some certainty that significant improvements in water quality can be achieved
through the targeted and integrated implementation of catchment management
interventions.
The catchment management intervention toolbox can be delivered through a variety of
approaches, which are described in more detail in the sections below.
Farm visits and advice
An integrated land management advice package will cover many aspects of a farmers
practice and will indicate where the adoption of good or best practice may minimise the
risk that an activity will have a negative impact on the environment and where it may
enhance the provision of a particular ecosystem service.
In addition to broad advice on good or best practice, an integrated farm advice package
should produce a targeted and tailored programme of measures that could be
undertaken and should include specific advice on pesticide, nutrient and soil
management on the farm to mitigate any potential environmental impacts.
Illustration showing some practices that can pose a threat to water quality (left side)
and a wide array of Best Farming Practices (BFPs) (right side) which can minimize loss
of pollutants to watercourses as a result of agricultural activity.

12. 12
Capital grants for on‐farm infrastructure
Where an advisor believes it to be appropriate, they will recommend in the
management plan that improvements or additions be made to the infrastructure on a
farm. Although some statutory designations, such as Nitrate Vulnerable Zones, do
require certain standards in on‐farm infrastructure, under most schemes the uptake of
these measures is entirely voluntary and the advisor will indicate funding mechanisms
through which a grant may be obtained to contribute to the total cost of the work.
Incentivisation to change farming practice
At present, farmers, who represent less than 1% of our society, currently manage nearly
80% of our countryside and are largely responsible for the health of the ecosystems it
supports. However, despite their key role in managing our natural ecosystems, farmers
are currently only paid for the provision of one ecosystem service; food production.
To redress this apparent imbalance, there are now a number of funding programmes
through which land managers and farmers can receive payments for adopting more
environmentally beneficial and ecosystem services‐enhancing practices on all or part of
their land. Schemes of this type, in which the beneficiaries of ecosystem services
provide payment to the stewards of those services, are often referred to as Payments
for Ecosystem Services (described in more detail in Assessing Improvements on p64).
The basic idea behind Payments for Ecosystem Services is that those who are
responsible for the provision of ecosystem services should be rewarded for doing so,
representing a mechanism to bring historically undervalued services into the economy.
Farming community engagement & education
Educational and training activities, such as farmer meetings and workshops, which raise
awareness of different initiatives and promote best practice among local farming
communities, are a key component of any catchment management programme. They
also serve to establish relationships and build trust between advisors and farmers on the
ground in a catchment.
LEAF (Linking Environment And Farming)
LEAF is the leading organisation promoting sustainable food and farming. They help farmers
produce good food, with care and to high environmental standards, identified in‐store by the
LEAF Marque logo. LEAF attempts to build public understanding of food and farming in a
number of ways, including; Open Farm Sunday, Let Nature Feed Your Senses and year round
farm visits to our national network of Demonstration Farms.
LEAF is also an industry partner in the Campaign for the Farmed Environment (CFE), which is an
opportunity for their members to demonstrate their commitment to protecting and enhancing
the farmed environment. As part of the Campaign, farmers are asked to ensure that a third of
their ELS points come from a list of key target options. These include options which result in
cleaner water and healthier soil, protect farmland birds and encourage wildlife and biodiversity.
LEAF also provide a wide array of educational and best practice guidance resources
on their website, including their Water Management Tool, which offers farmers a
complete health check for water use on their farms, and the Simply Sustainable
Water Guidance booklet and film. The Simply Sustainable Water booklet has been
produced to help farmers develop an effective on‐farm management strategy for
efficient water use and to improve their farm’s contribution to protecting water in
the environment. It allows farmers to get the best from this valuable resource, to
improve awareness of the importance of water and track changes in water use and
quality over time.
Based on Six Simple Steps to help improve the performance, health and long term
sustainability of their land, farmers are encouraged to set a baseline by assessing
their water use and their water sources. The six key measures are: (1) water saving
measures, (2) protecting water sources, (3) soil management, (4) managing
drainage, (5) tracking water use, and (6) water availability and sunshine hours.
CASE STUDY
Devon Wildlife Trust

13. 13
Delivery methods for catchment management
At present there are a number of different programmes and initiatives via which
catchment management interventions are funded to deliver catchment‐scale
improvements in water quality through the delivery of land management advice and on‐
farm measures.
Perhaps the most significant of these are; the Natural England‐coordinated Catchment
Sensitive Farming initiative, some elements of the Natural England Environmental
Stewardship Scheme and a number of newly established water company‐funded
schemes, such as the South West Water Upstream Thinking Initiative and the United
Utilities Sustainable Catchment Management Programme (SCaMP).
In addition to these programmes, the Environment Agency, Natural England, the
Forestry Commission and a number of non‐governmental organisations also make
considerable investment of their resources in the delivery of advice and practical
support for people managing natural resources in the catchment.
Each of these catchment management programmes have different funding mechanisms
and use different methods to target and deliver funding. For example, Catchment
Sensitive Farming offers small‐medium grants (up to £10,000 per farm) for capital
investments in farm infrastructure in its priority catchments alongside a programme of
advice and training. In contrast, Environmental Stewardship Schemes offer revenue
payments in return for the delivery of a suite of on‐farm measures in their target areas.
Catchment Sensitive Farming
Funded by DEFRA and the Rural Development Programme for
England, Catchment Sensitive Farming (CSF) is a joint initiative
between the Environment Agency and Natural England that has
been established in a number of priority catchments across England.
CASE STUDY
Overall, CSF has two principle aims: (1) to save farms money by introducing careful nutrient and pesticide planning,
reduce soil loss and help farmers meet their statutory obligations such as Nitrate Vulnerable Zones, and (2) to deliver
environmental benefits such as reducing water pollution, cleaner drinking water, safer bathing water, healthier fisheries,
thriving wildlife and lower flood risk for the whole community.
To achieve these goals CSF delivers practical solutions and targeted support which should enable farmers and land
managers to take voluntary action to reduce diffuse water pollution from agriculture to protect water bodies and the
environment.
Catchment Sensitive Farming Officers work with independent specialists from the farming community to deliver free
advice tailored to the area and farming sector. This advice includes workshops, farm events and individual farm
appraisals. CSF also offer capital grants, at up to 60% of the total funding, to deliver improvements in farm
infrastructure.
As part of the Catchment Sensitive
Farming programme, Natural England
have also undertaken an evaluation
study to demonstrate the benefits
that the delivery of advice and
measures have realised.
In addition to a summary report
(http://tinyurl.com/mzyrpc7), Natural
England have also produced a number
of case studies and technical reports
covering specific areas; such as,
advice and education delivery, water
quality monitoring and environmental
modelling. These can be accessed at
http://tinyurl.com/pk5rulg.

14. 14
Like Catchment Sensitive Farming, the South West Water Upstream Thinking initiative
also offers capital grants for on‐farm infrastructure improvements, but it also places
conditions on the management of the new infrastructure and on other activities
undertaken on the farm following the investment via a deed of covenant.
In addition, the Westcountry Rivers Trust, along with DEFRA and the University of East
Anglia, have recently investigated the potential of an innovative ‘reverse auction’
approach to target the allocation of funding in a catchment (see below). This work,
undertaken on the River Fowey as part of the Upstream Thinking Project and as part of
a DEFRA Payments for Ecosystem Services (PES) Pilot Project has demonstrated the
cost‐effectiveness of this method for the distribution of catchment management
funding.
Upstream Thinking
South West Water (SWW) in collaboration with a group of regional
conservation charities, including the Westcountry Rivers Trust, the
county Wildlife Trusts for Devon and Cornwall and The Farming
and Wildlife Advisory Group, have established one of the largest
and most innovative conservation projects in the UK: the ‘Upstream
Thinking Initiative’.
This project will deliver over £9 million worth of strategic land
restoration in the Westcountry between 2010 and 2015.
CASE STUDY
The ‘provider is paid’ funding mechanism used in the Upstream Thinking scheme is, perhaps, the most innovative aspect
of the project. SWW have recognized that it is cheaper to help farmers deliver cleaner raw water (water in rivers and
streams) than it is to pay for the expensive filtration equipment required to treat polluted water after it is abstracted
from the river for drinking. SWW believe that water consumers will be better served and in a more cost‐effective
manner if they spend money raised from water bills on catchment restoration in the short term rather than on water
filtration in the long term. The entire 5 year initiative will cost each water consumer in the South West around 65p.
Fowey River Improvement Auction
In the first scheme of this kind in the UK, an auction was successfully
used to distribute funds from a water company to farmers, investing
in capital items to improve water quality. The work was supported by
the Natural Environment Research Council Business Internship
scheme, managed by the Environmental Sustainability Knowledge
Transfer Network.
The scheme offered SWW the opportunity to work directly with
researchers from the University of East Anglia to devise an
innovative mechanism for paying for the delivery of ecosystem
services via their Upstream Thinking scheme.
Upstream Thinking uses an advisor‐led approach in other areas.
Advisors from the Westcountry Rivers Trust visit farms to suggest
work and pay grants at a fixed rate. The disadvantages of this
approach are that it’s labour intensive, not practical to visit all farms
and the potential for all the funds to be used on a small number of
farms. The main advantage is that advisors can suggest investments
most likely to improve water quality.
The University of East Anglia devised an auction approach, working with Westcountry Rivers Trust to: (1) increase
coverage by encouraging all eligible farmers to participate, and (2) achieve maximum water quality benefits at the same
time as achieving efficiency for SWW’s investment.
150 farmers in the Fowey catchment, were contacted in Summer 2012 with a list of capital investments eligible for
funding, plus additional farm management practices which could be added to increase bid competitiveness.
Farmers were asked to enter sealed bids up to a maximum of £50,000 per farm.
42 bids were received, requesting a total of £776,000 and 18 bids met the value for money threshold, with grant rates
paid in the scheme from 38% to the full 100%.

15. 15
Assessing the efficacy of interventions
The principal, over‐arching aim of catchment management is to improve raw water
quality in lakes, rivers and coastal waters. If effective, this approach could make a
significant contribution to their attainment of good ecological status, in accordance
with the EU Water Framework Directive.
In addition, it could also reverse the escalating risks and costs associated with the
treatment of drinking water from our groundwater and surface water sources and it
could reduce the impacts of pollution on our most sensitive and highly productive
estuaries and coastal environments.
Given the potentially significant role of this approach in the improvement of water
quality, it is vital for that we collect sufficient evidence to provide an objective and
scientifically robust assessment of the effectiveness of the interventions used.
Ultimately, we must be able to justify that the money spent and the interventions
delivered across the landscape have delivered both significant improvements in water
quality and a number of secondary financial, ecological and social benefits.

In this review we have attempted to collect a comprehensive and robust set of data and
evidence, which, taken together, demonstrates qualitatively and quantitatively that the
delivery of integrated catchment management interventions can deliver genuine
improvements in water quality.
In sections 2 to 6 we have, for each of the main groups of pollutants, identified key
sources of pollutant loads and examined the impacts these pollutants have on the
aquatic environment, including how they translate into a cost or risk to society.
We have also identified key mitigation measures for reducing pollutant loads and
evaluated the data and evidence for the efficacy of these measures. This process has
also allowed us to identify the interventions for which the evidence of efficacy does
not exist or where it does not exist at an appropriate scale.
Section 7 addresses issues of scale and reviews a selection of modelling tools that
can be used to predict the impact of interventions and measures at a larger sub‐
catchment or whole‐catchment scale. This section also explores the potential for
secondary environmental, economic and societal benefits to result from the delivery
of catchment management interventions.
Section 8 reviews the governance structures currently being used to implement a
catchment management‐based approach in the UK and explores some of the
approaches now being adopted to create catchment management plans.
Determine water quality impacts
Identify & qualify pressures
Locate sources & pathways
Develop programme of measures
Fund & deliver measures
Measure improvements
Record secondary benefits
A summary of the cyclical and adaptive
catchment management process: from
the characterisation of impacts to the
identification of pressures and on to
the delivery of measures and the
evaluation of improvements achieved.
Assessing fish populations using electrofishing

16. 16
NUTRIENTS
& ALGAE
NUTRIENTS & ALGAE

17. 17
Nitrogen‐ and phosphorus‐containing compounds (often termed nutrients) are natural
and vital components of healthy aquatic ecosystems. They play a critical role in
supporting the growth of aquatic plants, which, in turn, produce oxygen and provide
habitats that support the growth and reproduction of other aquatic organisms.
Nitrogen‐ and phosphorus‐containing nutrients also support the growth of algae,
another natural component of many aquatic ecosystems. Algae occur in the benthic and
planktonic phases of freshwater habitats and form a key component of the food chain
for many species of fish, shellfish and invertebrate assemblages.
Unfortunately, when nutrients are released into the environment, deliberately or
accidentally, as a result of human activities, it can result in a perturbation of the finely
balanced equilibrium of nutrients cycling through the ecosystem.
When nutrients accumulate in aquatic ecosystems they drive the uncontrolled and
unbalanced growth of aquatic plants and algae in a process called eutrophication and
these so‐called plant or algal ‘blooms’ can then cause severe problems for other aquatic
organisms, the ecological health of a waterbody and for the humans who also depend
on the water for drinking water, recreational use or for the production of food such as
fish and shellfish.
Sources of nutrients
There are three principal sources of nitrogen‐ and phosphorus‐containing compounds in
a river catchment: point anthropogenic sources, point agricultural sources and diffuse
agricultural sources.
Point anthropogenic sources. A considerable fraction of the phosphorus in river
water may be derived from inputs of sewage effluent (which may or may not have
been treated), from drainage systems in urban areas, septic tanks and from roadside
drains. The principal sources of phosphates and nitrates in sewage are human faeces,
urine, food waste, detergents and industrial effluent that have been discharged to
the sewers. Typical sewage treatment processes generally remove 15‐40% of the
phosphorus compounds present in raw sewage and there are many small sewage
treatment facilities and septic tanks in rural areas which could also be making
significant contributions to the phosphorus load in rivers and reservoirs.
Point agricultural sources. These include farm infrastructure designed to store and
manage animal waste and other materials such as animal food. Key infrastructure
includes dung heaps, slurry pits, silage clamps and uncovered yards. Animal access
points to watercourses can also lead to the direct delivery of phosphorus compounds
to the water and to their mobilisation following channel substrate disturbance.
Diffuse agricultural sources. When large amounts of manure, slurry or chemical
phosphorus‐containing fertiliser are applied to land, and this coincides with
significant rainfall, it can lead to run‐off and the transfer of phosphorus into
watercourses. This is a particular problem where heavy soils are farmed intensively,
which can result in their compaction and an increased risk of surface run‐off.
There are a number of methods that can be used to estimate the level of nutrient
enrichment in a watercourse and to determine where this contamination has been
derived from. For example, it is widely accepted that a detailed evaluation of the
benthic algae (diatom) communities in a river can provide a robust assessment of its
ecological condition, because these diatom communities are particularly sensitive to
changes in the pH and nutrient levels in the water.
In addition to biological assessments, water quality monitoring can also be used to
characterise the levels of nutrient enrichment in rivers and identify which sections of a
catchment are contributing most to the nutrient load at any particular location.
However, water quality sampling can be costly and time consuming, when undertaken
at fine temporal or spatial scales, and much of the work to identify sources of nutrient
pollution in river catchments has therefore focused on the use of models such as the
Extended Nutrient Export Coefficient Plus (University of East Anglia), the Phosphorus
and Sediment Yield CHaracterisation In Catchments (PSYCHIC) model (ADAS Water
Quality) and the new Source Apportionment GIS (SAGIS) tool (Atkins UK).
NUTRIENTS & ALGAE
Robert Marshall
NUTRIENTS & ALGAE
There are numerous potential sources
of nutrients in river catchments;
including sewage discharges (top),
agricultural point sources such as slurry
stores (middle) and diffuse sources such
as fertiliser applied to agricultural land
(bottom).

18. 18
CASE STUDY
Source Apportionment-GIS (SAGIS) modelling framework
The Source Apportionment‐GIS (SAGIS) modelling framework was developed through UWKIR research project WW02:
Chemical Source Apportionment under the WFD (UKWIR, 2012) with support from the Environment Agency. The
primary objective of this research was to develop a common modelling framework as the basis for deriving robust
estimates of pollution source contributions that would be used to support both water company business plans and the
EA River Basin Planning process.
The SAGIS tool quantifies the loads of pollutants to surface waters in the UK from 12 point and diffuse sources including
wastewater treatment works discharges, intermittent discharges from sewerage and runoff, agriculture, soil erosion,
mine water drainage, septic tanks and industrial inputs (UKWIR project WW02). Loads are converted to concentrations
using the SIMulation of CATchments (SIMCAT) water quality model, which is incorporated within SAGIS, so that the
contribution to in‐stream concentrations from individual sources can be quantified.
Diffuse sources of nutrient pollution are incorporated into SAGIS from the Phosphorus and Sediment Yield
CHaracterisation In Catchments (PSYCHIC) model (developed by a consortium of academic and government
organisations led by ADAS Water Quality).
PSYCHIC is a process‐based model of phosphorus and suspended sediment mobilisation in land runoff and subsequent
delivery to watercourses. Modelled transfer pathways include release of desorbable soil phosphorus, detachment of
suspended solids and associated particulate phosphorus, incidental losses from manure and fertiliser applications, losses
from hard standings, the transport of all the above to watercourses in under‐drainage (where present) and via surface
pathways, and losses of dissolved phosphorus from point sources.
The maps below show the baseline export of total phosphorus from manure‐based sources across the Tamar catchment
predicted by the PYCHIC model (inset) and the modelled concentrations of Soluble Reactive Phosphate in sub‐
catchments of the Tamar and their sources according to the SAGIS modelling tool (main).
NUTRIENTS & ALGAE

19. 19
Impacts of nutrients
On the health of aquatic ecosystems
The principal effect of accelerated plant growth and algal blooms is the reduction
(hypoxia) or elimination (anoxia) of oxygen in the water as oxygen‐consuming bacteria
decompose the plants and algae when they die back. This reduction in the oxygenation
of a waterbody can have a severe effect on the normal functioning of the ecosystem,
causing a variety of problems such as a lack of oxygen needed for fish, shellfish and
invertebrates to survive.
Under the Water Framework Directive (WFD) classification scheme the ecological
impacts of nutrients on freshwater systems are recorded through the changes that they
exert on the plant and algal communities that are found in them. Changes in the
composition of these communities are interpreted as an indication that nutrient
enrichment is perturbing the ecological health of the ecosystem in that waterbody.
The impact of nutrients on the health of estuaries and coastal areas is still relatively
poorly understood but, as with freshwaters, excessive nutrient loads can cause their
eutrophication. The susceptibility of estuaries to nutrient enrichment depends on
factors such as the physical characteristics, the hydro‐dynamic regime and the biological
processes that are unique to each individual estuary. Generally speaking, estuaries and
coastal areas are thought to be less susceptible to eutrophication due to their tidal
nature, which results in high turbidity (less light penetration) and frequent flushing.
Estuaries with good light regimes are often more sensitive to nutrient enrichment.
Primary producers in estuaries may be opportunistic green algae, epiphytes or
phytoplankton and excessive growth of any or all of these can impact on water turbidity
and light availability, causing changes in the depth distributions of plant communities in
the water column. Such changes can have implications for the structure and functioning
of estuarine and coastal food webs, with potential consequences for fish and shellfish
fisheries and for bathing water quality on neighbouring beaches.
In addition to the assessment of these biological indicators, the levels of Soluble
Reactive Phosphorus (SRP) in waterbodies are also measured and, through comparison
with established thresholds known to cause ecological impacts, the levels are used to
identify where degradation might be expected to occur. The WFD threshold above
which SRP is expected to have a significant impact on the ecological condition of an
aquatic ecosystem varies between different waterbody types, but an average SRP
concentration above 50 ug/l would result in a WFD failure in any waterbody type.
Bob Blaylock
The Exe Estuary at Topsham
NUTRIENTS & ALGAE
Water starworts (Callitriche spp) (top)
are just one group of macrophyte
plants that can cause problems when
they proliferate excessively. Phyto‐
benthic algae (diatoms) are particularly
sensitive to nutrient enrichment
(bottom).

20. 20
On the provision of drinking water
In addition to the ecological impacts of nutrient enrichment leading to hypoxia and/or
anoxia in aquatic ecosystems, algal blooms can also result in other negative effects that
have significant consequences for the treatment and supply of drinking water.
These include their potential to damage property or water supply infrastructure, to
increase algae‐derived toxins in the water and to cause taste and odour problems, all of
which can result in increased drinking water treatment costs.
These impacts are particularly felt as blooms of algae and explosions of macrophyte
growth begin to die‐back at the end of the summer growing season or following the
depletion of nutrients and oxygen in the water column, when a number of so‐called
decomposition bi‐products can be released.
The three principal types of chemical pollutants produced as decomposition bi‐products
of this type are: (1) ammonia/ammonium (NH4), (2) soluble organic compounds (e.g.
methyl‐isoborneol (MIB) and geosmin) and (3) dissolved metal ions (e.g. manganese).
Ammonia and its ionised cationic form ammonium (NH4+) are naturally occurring
components of the nitrogen cycle that are generated in aquatic ecosystems by
heterotrophic bacteria as the primary nitrogenous end‐product of organic material
decomposition. In healthy aquatic ecosystems ammoniacal nitrogen is readily
assimilated by plants or converted through nitrification to nitrate, but in eutrophic lakes,
where elevated levels of nutrients are driving algal blooms and the development of
stratified hypoxic conditions, this process can be inhibited and ammoniacal nitrogen
then accumulates rapidly.
The presence of ammoniacal nitrogen in water can begin to have a toxic effect on
aquatic organisms (especially fish) at concentrations above 0.2 mg/l. In addition, when
abstracted for drinking water treatment, ammoniacal nitrogen concentrations above
0.2 mg/l can also cause taste and odour problems as well as decreased disinfection
efficiency during chlorination.
The increased chlorination required to remove ammoniacal nitrogen during the
treatment process can also lead to the indirect generation of dangerous chemical bi‐
products such as trihalomethanes (THMs), which are thought to have toxic and/or
carcinogenic properties and are very difficult to remove from the final treated drinking
water. Furthermore, increases in the nitrification of ammonia in the raw water, and the
increased consumption of oxygen that this entails, may also interfere with the removal
of manganese by oxidation on the filters, which can result in the production of mouldy,
earthy‐tasting water.
In 2002 the Environment Agency commissioned the University of Essex to undertake an
assessment of the environmental costs resulting from the eutrophication of fresh water
ecosystems in England and Wales. Their findings, summarised in the table below,
revealed that the total damage costs were in the range of £75 to £114 million.
Summary of the annual costs associated
with freshwater eutrophication in the
UK. Costs were calculated as ’damage
costs’ – i.e. the reduced value of clean
or non‐nutrient‐enriched water
(adapted from Pretty et al., 2002).
Cost categories
Range of annual costs
(£ million)
Social damage costs
Reduced value of waterside dwellings £9.83
Reduced value of waterbodies for commercial use (abstraction, navigation, livestock, irrigation and industry) £0.50 ‐ 1.00
Drinking water treatment costs (treatment and action to remove algal toxins and algal decomposition products) £19.00
Drinking water treatment costs (to remove nitrogen) £20.10
Clean‐up costs of waterways (dredging, weed‐cutting) £0.50 ‐ 1.00
Reduced value of non‐polluted atmosphere (via greenhouse and acidifying gas emissions) £5.12 ‐ 7.99
Reduced recreational and amenity value of water bodies for water sports, angling, and general amenity £9.65 ‐ 33.54
Revenue losses for formal tourist industry £2.94 ‐ 11.66
Revenue losses for commercial aquaculture, fisheries, and shellfisheries £0.029 ‐ 0.118
Health costs to humans, livestock and pets unknown
Ecological damage costs
Negative ecological effects on biota (arising from changed nutrients, pH, oxygen), resulting in changed species composition
(biodiversity) and loss of key or sensitive species
£7.34 ‐ 10.12
TOTAL £75.0 ‐ 114.3
NUTRIENTS & ALGAE

21. 21
Mitigation measures & their efficacy
There are a wide range of mitigation measures available for reducing nutrient inputs
into the aquatic environment.
Soil, land and slurry management
Limiting fertiliser and manure inputs to suit crop requirements prevents over‐use and
reduces the quantities of surplus nutrients entering the system. Mitigation measures to
limit nitrogen inputs to suit crop requirements have been shown to substantially reduce
nitrate losses from soil (Lord and Mitchell, 1998), but these methods are less effective in
reducing phosphorous concentrations in run‐off due to phosphorous build‐up in soil.
Mitigation measures to reduce nutrient loads through changes in agricultural land and
soil management practices include the use of fertiliser placement technologies and
avoiding application of fertiliser to high‐risk areas. There are also a variety of
conservation tillage techniques that can be implemented, with the aim of reducing
nutrient losses via surface run‐off.
Mitigation measures for improved soil, land and slurry management are listed below
and the evidence for their efficacy is summarised in the table below:
Implementation of conservation tillage techniques
Fertiliser spreader calibration
Use of a fertiliser recommendation system
Use of fertiliser placement technologies
Re‐site gateways away from high‐risk areas
Do not apply fertiliser to high‐risk areas
Avoid spreading fertiliser to fields at high risk times
Do not apply P fertiliser to high P index soils
Install covers on slurry stores
Increase the capacity of farm manure storage
Minimise volume of dirty water and slurry produced
Change from slurry to solid manure handling system
Reference Mitigation Measure Findings
Benham et al. (2007) Implementation of conservation tillage
techniques
Mean losses in surface run‐off for
total nitrogen was reduced by 63%
ammonia was reduced by 46%
nitrate was reduced by 49%
total phosphorus was reduced by 73%
Daverede et al. (2004) Injection of slurry 93% reduction in dissolved reactive P in run‐off
82% reduction in total P in run‐off
94% reduction in algal‐available P in run‐off
Deasy et al. (2010) Tramline management Tramline management reduced nutrient and sediment
losses by 72‐99% on 4 out 5 sites and were a major
pathway for nutrient transfer from arable hill‐slopes
Goss et al. (1988) Direct drilling Winter losses of nitrogen was on average 24% less than
for land that had been ploughed
Johnson and Smith (1996) Shallow cultivation (instead of ploughing) Decreased nitrogen leaching by 44 kg per hectare over
a 5 year period
Pote et al. (2003) Incorporation of poultry litter in soil 80‐90% reduction in nutrient losses from soil
Pote et al. (2006) Incorporation of inorganic fertilisers into
soil
Reduction of nutrient losses to the water environment
to background levels
Shephard et al. (1993, 1996 and
1999), Goss et al. (1998), Lord et
al. (1999)
Planting a green cover crop 50% reduction in nitrate losses compared to winter‐
sown cereal. Uptake of nitrogen ranging between 10
and 150 kg per hectare
Withers et al. (2006) Ensure tramlines follow contours of the land
across the slope
No significant differences in run‐off quantity, sediment
and total phosphorous loads compared to areas with no
tramlines
Zeimen et al. (2006) Ensuring a rough soil surface by ploughing
or discing
Transport of soluble phosphorus in surface run‐off
reduced by a factor of 2‐3 compared to untilled soils
The table below summarises key
findings of research into the efficacy of
mitigation measures aimed at limiting
nutrient losses by changing agricultural
land and soil management practices.
These findings are a result of research
carried out at either a plot‐ or field‐
scale.
NUTRIENTS & ALGAE
The Westcountry Rivers Trust have
produced a series of farm‐measure fact‐
sheets, which can be found on the
DEFRA website at—http://tinyurl.com/
kqpyctv.

22. 22
CASE STUDY
River Otter Catchment Management Project
The River Otter rises in the Blackdown Hills in East Devon and runs for approximately 25 miles southwest to the sea.
Below Honiton, the Otter enters its floodplain and runs south through several towns and villages before reaching the salt
marshes at Budleigh Salterton. In its lower reaches, the Otter becomes a gravel‐bed river that meanders through rolling
topography with mixed agricultural land use, including livestock, cereals, oil seeds, fruit and vegetables.
Issues
Due to the sandy nature of the soils in the Otter catchment, leaching of nitrate and pesticides is common. South West
Water (SWW) relies heavily on the lower Otter boreholes to meet local drinking water demands and many of these
boreholes have shown worrying trends in nitrate levels. Sediment and phosphate levels in surface waters are also high
and in need of attention.
High nitrate levels increase the burden of supplying potable water and, although the SWW Dotton treatment plant is
capable of blending and stripping excess nitrate from the extracted water, its capacity is limited. Reducing the nitrate
content in raw water will reduced this burden and its associated economic and environmental costs.
Delivery of Interventions
Farm visits were made to engage with farmers and explain the benefits of better
nutrient management. Where appropriate, farmers were provided with farm reports to
highlight priority areas likely to influence raw water quality and to provide advice on
management practices to reduce pollutant loads. From 2010‐2012, thirty‐seven farms
were visited and eight received farm reports. Events were also held to engage with the
farming community whilst at the same time to bolster the understanding of the project
aims. Events have included fertiliser spreader workshops, crop trial workshops and
visits to the SWW water treatment works.
Following the visit to the water treatment works one farmer commented that the
project was, “...very interesting. Our strategy has more influence on water quality than I
thought...”.
Monitoring & Outcomes
Focusing on the nitrate contribution from agriculture, a monitoring study was set up to assess the relative contributions
from different land use types within the catchment and to monitor changes in nitrate levels following farm visits.
Ten geographically diverse farmers kindly gave permission to use a single field on each of their farms for testing, pre‐ and
post‐winter. Each farm was chosen carefully to ensure a representative selection of land use types were included.
The nitrate testing sites were selected in 2010 and sampling was undertaken in November 2010, March and November
2011, March and November 2012 and March 2013. The difference in nitrate levels recorded in the soil between November
and March gives a value for nitrogen lost over winter.
The chart (left) shows that overall levels of nitrogen lost
from the soil has decreased significantly over the
monitoring period, with levels in 2012/2013 approximately
a third of the level lost over the 2010/2011 winter.
The amount of nitrogen used by the current crop has been
taken into account, where appropriate, and the remaining
fraction of nitrogen unaccounted for is considered to be
associated with the export of animal products, crops,
leaching, de‐nitrification and volatilisation. In most cases,
the nitrogen loss will mainly be associated with leaching,
volatilisation and de‐nitrification, all of which are
environmentally damaging.
While these results are encouraging, there are several other factors that could have contributed to this reduction, such as
the weather, and it is not possible to prove that these positive results are directly linked to interventions. However, they
do offer a snapshot of the problems faced in this area and certainly point towards a positive impact resulting from the
provision of nutrient advice on farm visits and in farm plans.
This monitoring work also provides invaluable data for the farmers participating in the project and helps to reinforce the
project aims, as demonstrated by positive farmer feedback.
NUTRIENTS & ALGAE

23. 23
Management of livestock
In their Europe‐wide study into the sources of phosphorus inputs into rivers, Morse et al
(1993) estimated that the most significant contributions were from livestock, human
waste and fertiliser run‐off sources (see chart right).
Mitigation measures designed to reduce nutrients inputs from livestock are listed below
and the evidence for their efficacy is summarised in the table below:
Reduction in stocking density
Reduction in dietary N and P intakes
Exclusion of livestock from waterbodies and provision of alternative drinking
sources
Exclusion of livestock from poorly drained areas of land to prevent poaching and
subsequent mobilisation of soils and nutrients
Reference Mitigation Measure Findings
Heathwaite and Johnes
(1996)
Reduced livestock grazing density Phosphorous exports in surface run‐off was recorded as:
 2 mg total P per m2
for ungrazed land
 7.5 mg total P per m2
for lightly grazed land
 291 mg total P per m2
for heavily grazed land
Huging et al. (1995) Reduce livestock grazing density There is a significant relationship between grazing intensity
and nitrogen losses to water
Nitrogen leaching losses were reduced by 69%
Kurz et al. (2006) Exclusion of livestock from poorly drained
areas of land to prevent poaching
Decreased concentrations of total nitrogen, organic phos‐
phorous and potassium were measured in surface run‐off
from un‐grazed areas when compared to grazed areas
Line (2003) Fencing the watercourse to exclude live‐
stock combined with a 10‐15m buffer‐strip
Total organic nitrogen load decreased by 33%
Total phosphorous load decreased by 76%
Parkyn et al.(2003) Fencing the watercourse to exclude live‐
stock
Streams within fenced off areas showed rapid improvement
in visual water clarity and channel stability
Soluble reactive phosphorous decreased by up to 33% in
some streams, although in others it increased
Total nitrogen decreased by up to 40% in some streams but
increased in others
Sheffield et al. (1997) Provision of alternative drinking source for
livestock
Total phosphorus load decreased by 54%
Total nitrogen load decreased by 81%
Exclusion of livestock from poorly drained areas of land to prevent poaching
Poaching around feeding and drinking areas can lead to soil damage, as well as stock welfare and pollution problems,
particularly during wet periods. Simple management changes can help farmers to benefit from:
improved stock health and lower vet bills
reduced soil damage, erosion, runoff and watercourse pollution
improved grass production and nutritional value
reduced sward restoration costs.
reduced risk of damage to environmentally sensitive areas
CASE STUDY
Careful management of out‐wintered stock and equipment in order to avoid serious
damage to soils and sward was undertaken on 5 ha of grassland. Regular inspections,
particularly in wet weather allowed movement to better‐drained areas before serious
poaching occurred.
This resulted in 10% less grass to be restored, encouraged early recovery and
provided an early spring “bite”. Annual savings included 10% less grass to be
reseeded @ £54/ha and 10% less loss of forage@ £24/ha. The total saving for 5ha
was £390 with an immediate payback.
Sources of phosphorus in the EU
NUTRIENTS & ALGAE

24. 24
Buffer Strips for nutrient pollution mitigation
Creation of riparian buffer strips along watercourses is perhaps the most widely recommended mitigation method for
controlling diffuse pollution losses from agriculture. Consequently, research into the efficacy of buffer strips in reducing
pollutant load entering watercourses has been extensive.
Efficacy (% reduction)
Reference Location Buffer Width (m) Soil Texture Slope (%) Phosphorous Nitrogen
Abu‐Zraig et al. (2003) Canada 2 Silt loam 2.3 57‐64
5 47‐60
10 5 65‐72
15 2.3 55‐93
Barfield et al. (1998) USA 4.6 9 92
9.1 100
13.7 97
Barker et al. (1984) 79 99
Blanco‐Canqui et al. USA 0.7 Silt loam 4.9 44‐63 62‐77
(2004) 54‐72 35‐36
22‐53
4 77‐82 82‐83
81‐91 54‐70
71‐84
8 87‐91 88‐90
96‐99 83‐84
87‐95
Borin et al. (2004) Italy 6 Sandy loam 3 78 72
Cole et al. (1994) 2.4‐4.9 Silt loam 6 93
Dillaha et al. (1988) UK 4.6 Silt loam 11‐16 73 27
49
9.1 93 57
56
Doyle et al. (1977) UK 1.5 Silt loam 10 8 57
62 68
A riparian buffer strip can be defined as a corridor of natural vegetation
between agricultural land and a watercourse. They act as barriers to surface
flows and therefore impact on delivery of pollutants to watercourses. The
rate of surface run‐off is slowed as the water meets resistance from
vegetation and flows over rougher and more porous surface material.
The substantial root systems beneath the surface also increase the likelihood
of infiltration. Slower flowing water has a reduced capacity for the transport
of particulate matter and, as a result, there is increased deposition of
sediment prior to surface flows reaching the watercourse.
CASE STUDY
There are numerous factors that may influence the performance of buffer strips in reducing pollutant load. These include
the characteristics of the incoming pollutants, the topography and soils of the land surrounding the watercourse and the
characteristics of the buffer strip itself, for example vegetation type and width. In addition, seasonal variations in
meteorological conditions and farming practices can also influence buffer strip performance.
The findings of the many studies into the efficacy of buffer strip in mitigating nutrient losses from farmland are shown in
the table below. These results illustrate the variability inherent in quantifying the efficacy of buffer strips in reducing
nutrient inputs to watercourses, with the range of efficacy for total phosphorus varying from 30 to 95% and for total
nitrogen, from 10 to 100%.
Continued over page...
NUTRIENTS & ALGAE

25. 25
Efficacy (% reduction)
Reference Location Buffer Width (m) Soil Texture Slope (%) Phosphorous Nitrogen
Duchemin & Madjoub 3 Sandy loam 2 85 96
(2004) 41
9 87 85
57
Edwards et al. (1983) UK 30 ‐ 2 47‐49
Knauer & Mander (89) Germany 10 ‐ 70‐80 50
Kronvang et al. (2000) Denmark 0.5 Sandy loam 7 32
29 100
Kronvang et al. (2004) Norway 5 Silt loam 12‐14 46‐78
10 80‐90
Lee et al. (2000) 7.1 Silty clay loam 5 28‐72 41‐64
Lim et al. (1998) USA 6.1 Silt loam 3 74.5 78
76.1
12.2 87.2 89.5
90.1
18.3 93.0 95.3
93.6
Magette et al. (1987) UK 9.2 Sandy loam 41 17
McKergow et al. (03) Australia Loamy land <2 6 23
Muenz et al. (2006) USA 25 Sandy clay loam 16.5 50 50
Patty et al. (1997) France 6 Silt loam 7‐15 22 47
18 89 100
Parsons et al. (1991) USA 4.3‐5.3 ‐ 26 50
Schmitt et al. (1999) 7.5 Silty clay‐loam 6 48 35
19
15 79 51
50
Schwer & Clausen 26 Sandy loam 2 89 92
(1989) 92
Smith (1989) New Zealand 10 ‐ 55 67
80
Syversen (1992) Norway 5 ‐ 65‐85 40‐50
10 95 75
Thompson et al. UK 12 ‐ 4 44
(1978) 36 70
Vought et al. (1995) Sweden 5 ‐ 40‐45 10‐15
10 65‐70 25‐30
15 85‐90 40‐45
Young et al. (1980) UK 27 ‐ 4 76‐96 82‐94
Zirschky et al. (1989) 91 Silt loam 38
Buffer Strips for nutrient pollution mitigation...continued….
NUTRIENTS & ALGAE

26. 26
Delivery of interventions
All thirteen farms in the Mill Creek catchment were paid to implement agricultural BMPs under a contract that calls for 10
year maintenance of the practices in return for the technical and financial assistance. Additionally two deed restrictions
were applied to two barns.
Mill Creek, Pennsylvania State, USA
The Mill Creek catchment drains into the Stephen Foster Lake in the northern mountain region of Bradford County,
Pennsylvania, USA. While greater than half of the surrounding 26 km2
catchment area is used for agricultural production,
the remainder is predominantly forested.
Over time Mill Creek has deposited excess sediment and nutrient run‐off into the 28 Ha lake. As a result, Pennsylvania
added Stephen Foster Lake to the state’s list of impaired waters in 1996 for nutrient and sediment runoff due to
agricultural activities. Subsequently, a Total Maximum Daily Load (TMDL) for the lake that called for reductions of 49%
for phosphorus was established.
CASE STUDY
Catchment management plan
Several computer models were used to estimate the load reductions that might result from Best Management Practices
(BMPs) being implemented. With the combination of these efforts, the nutrient runoff was estimated to be reduced by
52% and sediment runoff reduced by 59%, exceeding the reduction recommended in the TMDL.
The suggested BMPs were primarily aimed at the control of nutrient inputs from animal wastes, which contribute an
estimated 175 kg of phosphorus (10% of the total annual load). Erosion control, to further reduce nutrient and sediment
loadings to the lake, are estimated to reduce the total phosphorus load in it by an additional 10%.
Manure and runoff from a previously severely degraded manure handling area is now
contained and directed to the new manure storage facility for field application.
Farm feedlot before and after infrastructure improvements.
Upstream of the lake, farmers and the Bradford
County Conservation District installed 9 miles of
stream fencing and alternative water supply
systems to help prevent cattle from wandering
into waterways.
Agricultural crossings, to swiftly move cattle
across streams and prevent the animals from
grazing near waterways and destroying
riverbanks were also constructed.
Project partners also built 11 systems to store and
treat animal waste, planted riparian buffers, and
restored 2,500 feet of stream channel. The
Bradford County Conservation District identified
over $518,000 worth of improvements to be
delivered over the 11 farms.
Growing Season Total Phosphate (TP) loads (kg) entering Stephen
Foster Lake before (1994‐95) and after (2004, 2005, 2006 & 2008‐09)
delivery of Best Management Practices
Monitoring & Outcomes
Pennsylvania Department for Environmental Protection conducted
biological monitoring and analysis of Mill Creek. Across the
catchment there were four sample stations collecting monthly
readings for pH, conductivity, a suite of Phosphate and Nitrogen
measurements, alkalinity, total suspended solids and temperature.
Since 2004 the growing season Total Phosphate (TP) load entering
Stephen Foster Lake declined by 50 to 90% relative to the original
Phase I study (1994‐95) load. As a result of these reductions, the
lake has been in compliance with its total phosphorus TMDL
targeted, growing season load since 2005.
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27. 27
CASE STUDY
Upper Tamar Lakes Farm Intervention Assessment
The farm is located in the Tamar Lakes Catchment and has a first order stream which runs next to the yard. The 98 Ha of
land is comprised of gently undulating pasture (60 Ha), arable (10 Ha in maize and 20 Ha in winter and spring barley) and
woodland. The main farm enterprise is a dairy with 130 milkers and 50 followers. There are around 60 bull calves and the
farmer has winter sheep kept over October to February. The dairy herd are housed over the winter months (September
to March) and the farm has approximately 4 months slurry storage capacity. Slurries are separated into a slurry lagoon
and three dirty water pits. The slurry is spread over the land by the farmer using the farm’s own machinery.
Intervention
Although the farmer demonstrated several good practices, there was a problem with his slurry store, which was
outdated, could not cope with the demands of the modern dairy and did not afford the environment with enough
protection against leaks and overflowing episodes. In this instance the ‘weeping wall’ slurry lagoon was placed too close
to watercourse and therefore ran the risk of polluting it.
In this situation the solution was to create a solid walled lagoon, which being slightly larger, allowed for slurry to be
removed and spread at appropriate times, as well as giving protection to the watercourse. The photographs below show
the formalisation of the slurry pit from an inadequate weeping wall system to a concrete, bunded system in early 2008.
Monitoring
Monitoring of aquatic invertebrates was undertaken and taxa scored against the BMWP scoring system (Biological
Monitoring Working Party ‐ National Water Council, 1981) to assess changes in agricultural pollution. Data was collected
over the term of the project from 2007 to 2009 and further monitoring was undertaken in 2012 to assess the long‐term
effects. Two sites one upstream and one downstream (separated by around 100m) allowed assessment of the impact of
the intervention.
Results
The results of the BMWP scores show that there is a
significant negative impact on water quality between
the upstream score (blue line) and the downstream
score (red line) in the first two samples before the
intervention. After the intervention in Early 2008 (green
line) the difference between the upstream and
downstream reduces suggesting that there is little
water quality difference between sites.
Although the 2012 upstream and downstream readings
are lower than the 2008 and 2009 readings there is still
little difference between the two suggesting that there
continues to be no impact from the site in terms of
water quality.
Monitoring
The river is a small first order stream, which goes part way to explaining the relatively low BMWP scores when compared
to second and third order streams in the area. It is highly likely that weeping wall slurry pit was having a significant
negative impact on downstream water quality and the intervention of formalising the pit reduced the difference between
the two survey sites, both immediately after the intervention and four years later. The decrease in upstream and
downstream scores in 2012 is likely to be wider environmental factors such as an increase summer rainfall.
BMWP scores upstream (blue) and downstream (red) of a farmyard with an
inadequate slurry pit with weeping wall. The slurry pit was updated in early
2008 (shown as an green line) after which the difference between the two
scores reduces. Whilst 2012 figures are reduced compared to 2008 & 2009 the
difference between upstream and downstream is less than before intervention.
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28. 28
SUSPENDED SOLIDS
& TURBIDIT Y
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& TURBIDITY

29. 29
Turbidity is a measure of how much suspended material there is in water. Turbidity is
reported in nephelometric units (NTUs), which are measured by an instrument
(turbidimeter or nephelometer) that estimates the scattering of light by the suspended
particulate material.
There are many factors that can cause the turbidity of water to increase, but the most
common are the presence in the water column of algae, bacteria, organic waste
materials (including animal waste and decomposing vegetation) or silt (soil or mineral
sediments). These materials are often released into the water following disturbance of
the river or lake substrate, but they can also enter the water as a result of erosion and
run‐off from the land.
Sources of suspended solids
Numerous methods have been developed to identify the sources of suspended solids
and the dynamics of sediment transport in rivers. These methods, which vary greatly in
the spatial scales at which they can be applied, include:
Fine sediment risk modelling. Uses topographic, rainfall and land‐use data to
identify areas where a high propensity for the lateral flow of water over the land is
likely to mobilise fine sediment and transport it to the river.
Sediment load sampling. Water sampling to determine suspended solid load and the
contribution being made by different sub‐catchments.
Sediment river walkover surveys. Rapid river surveys typically undertaken in wet
weather to identify sources of sediment and organic material entering the river.
Source apportionment using fluorescent, chemical and genetic signatures.
Pioneered by research organisations, such as ADAS Water Quality and the University
of Plymouth, these approaches allow the areas of river bank or land that are
contributing to the in‐channel sediment load to be identified.
Overall these studies reveal that the sediment load in rivers is derived from point or
diffuse sources in three principal locations:
Material from the river channel and banks
Soil and other organic material washed off from the surface of surrounding land
Particulate material from anthropogenic sources; including point sources, roads,
industry and urban areas.
SUSPENDED SOLIDS & TURBIDIT Y
SUSPENDED SOLIDS
& TURBIDITY
Examples of sediment being mobilised
from the land surface (in this case a
country road; top) and entering a
watercourse (bottom).

30. 30
SCIMAP: A fine sediment risk modelling framework
A simple and robust fine sediment risk model can be extremely beneficial as it helps us to target and tailor both further
monitoring work and catchment management interventions.
The SCIMAP fine sediment risk model was developed through a collaborative project between Durham and Lancaster
Universities. The SCIMAP Project was supported by the UK Natural Environment Research Council, the Eden Rivers Trust,
the Department of the Environment, Food and Rural Affairs and the Environment Agency.
The SCIMAP model gives an indication of where the highest risk of sediment erosion risk occurs in the catchment by (1)
identifying locations where, due to landuse, sediment is available for mobilisation (pollutant source mapping) and (2)
combining this information with a map of hydrological connectivity (likelihood of pollutant mobilisation and
transportation to receptor).
The combination of the sediment availability and hydrological connectivity maps results in a final fine sediment erosion
risk model that is useful for targeting field surveys and the mitigation of erosion risk at catchment, farm or field scale.
CASE STUDY
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31. 31
Impacts of suspended solids & turbidity
On the health of aquatic ecosystems
The most obvious effect of turbidity on the quality of water is aesthetic, as it gives the
appearance that the water is dirty. However, suspended material in the water of rivers
and lakes can also cause significant damage to the ecology of the aquatic ecosystem by
blocking the penetration of light to aquatic plants, clogging the gills of fish and other
aquatic organisms, and by smothering benthic habitats. This has the effect of
suffocating the organisms and eggs that reside in the interstitial spaces of the substrate.
Furthermore, where elevated turbidity is the result of algal or other microbial growth
these organisms can also have direct toxic effects on the ecology of the ecosystem (e.g.
toxic blue‐green algae) or indirect effects through the eutrophication of the water
column.
Suspended material in rivers and streams can also have a significant impact on the
ecological health, productivity and safety of estuarine and coastal environments in the
downstream sections of their catchments.
On the provision of drinking water
In addition to their ecological impacts, turbidity and suspended solids also add
significantly to the intensity and cost of drinking water treatment as they can
accumulate in and damage water storage and treatment infrastructure.
Suspended sediment must also be eliminated from the water for effective chlorine
disinfection of the water to be achieved.
Furthermore, particulates in suspension also carry other damaging and potentially
dangerous pollutants, including metals, pesticides and nutrients (such as phosphorus).
Once removed from the water, the resulting sludge, which may be contaminated with
these other pollutants, must also be disposed of in a safe manner and this can be
extremely costly when it is produced in large volumes.
In light of the impact that turbidity and suspended solids have on the efficiency and cost
of water treatment and on the aesthetic quality and safety of the final drinking water, it
is little surprise that the UK Water Supply (Water Quality) Regulations 2000 indicate
that treated drinking water should not have turbidity above 1 NTU.
In addition, the EC Directive on the Quality Required of Surface Water Intended for the
Abstraction of Drinking Water 1975 (75/440/EEC) gives guidance that raw water should
not have Total Suspended Solids (TSS) above a concentration of 25 mg/l without higher
levels of treatment being undertaken before consumption.
In the water treatment processes undertaken at water treatment works, the suspended
material in the raw water, and hence the turbidity, is removed by coagulation induced
by the addition of various coagulants (e.g. alum). The level of turbidity in the raw water
has a significant effect on the coagulation process. When turbidity is elevated, the
amount of coagulant added must be increased and, at many treatment works, turbidity
(along with colour) is one of the parameters that is constantly measured and used to
calibrate the dose of coagulant used in the treatment process.
Sediment pressure is felt at the
sediment or sludge press of the water
treatment works (top). This generates
large quantities of sediment or sludge
‘cake’ which must then be safely
disposed of (bottom). Data indicate
that raw water polluted with
suspended sediment can double or
even triple the amount of sludge
created at a works.
Sediment accumulation on a riverbed
SUSPENDED SOLIDS
& TURBIDITY