The Chartered Institution of Water and Environmental Management
(CIWEM) is the leading professional and qualifying body for those
responsible for the stewardship of environmental assets. The
Institution also provides independent comment on water and
environmental management and sustainable development. This paper
sets out recommendations for tackling diffuse pollution.
Diffuse pollution originates from hundreds or thousands of small
sources, or is washed off land with rainfall. It is distinct from
point sources like discharges of wastewater from industrial
treatment plants, and it is more difficult to control.
Diffuse pollution is now more evident since the quality of point
source discharges has been improved. Diffuse pollution can affect
water supplies, effluent disposal, industry, fisheries, recreation,
and conservation. Most diffuse pollutants stem from the use of land
for agriculture, forestry, industry and from urban land.
CIWEM is pleased that the Department for Environment, Food and
Rural Affairs (defra) has set out its priorities for policy in
Directing the Flow . This recognises the significance of diffuse
CIWEM's Position on Diffuse Pollution of Water
- CIWEM seeks cost effective policy measures for addressing
diffuse pollution, developed in consultation with stakeholders.
CIWEM supports approaches that emphasize outcomes and achieve
specific reductions of risks.
- CIWEM supports the promise in Directing the Flow to review, and
to consult more widely on problems caused by agricultural
- CIWEM supports the way in which the forestry, agriculture and
construction industries have adopted "codes of good practice".
These should be written into binding Codes of Practice under the
Water Framework Directive.
- CIWEM suggests that a statutory Code of Practice should be
developed along the lines of the present Environment Agency's 'Best
Farming Practices' and the Scottish Agricultural Pollution Group's
PEPFAA (Prevention of Environmental Pollution from Agricultural
Activity) codes. This would address risks to drinking water,
bathing water and from eutrophication.
- CIWEM suggests stronger incentives to prevent pollution. These
can include, cost-savings, the avoidance of fines and tax
- CIWEM seeks to ensure that land use planning guidance and good
practice at both national and regional level takes more account of
- CIWEM advises that more emphasis be placed on the risks to
private water supplies.
- CIWEM wants more research, and more collaborative research, on:
- urban diffuse pollution, and policy options to address it;
- implications of land-use planning decisions;
- scope for sustainable drainage systems (e.g. SuDS) to help to
prevent pollution; and,
- the cost-effectiveness of options to alleviate and prevent
- CIWEM seeks more weight for the biodiversity implications of
options for addressing diffuse pollution, and the promotion of
sustainable farming practices.
- In determining action, CIWEM believes that because of the
multitude of stakeholders involved that all the costs and benefits
need to be taken into account. The involvement of different groups
should also be identified clearly. Those responsible for pollution
should pay most of the costs. This should lead to more effort to
control discharges to and from surface water sewers, and to reduce
chemicals entering the environment.
- CIWEM suggests that EC Directives take more account of costs
and benefits before they are agreed and before being transposed to
UK law a Regulatory Impact Assessment (RIA) is undertaken. A wider
range of stakeholders should be involved in the consideration of
proposals for Directives.
- Such a cost benefit appraisal should consider the principles of
sustainability, the environmental, social and economic costs, and
the search for solutions that give most overall value and benefit
- In promoting a more sustainable agriculture CIWEM supports
reforms of the Common Agricultural Policy to take account of
environmental directives, including water, and encourage
improvements to environmental performance.
1 Directing the Flow - Priorities for
future water policy, published by Defra in November 2002
Background information: sources and impacts of diffuse
Industrial activities may generate diffuse pollution by oils and
hydrocarbons, sediment, phosphorus, iron, acidifying pollutants
through atmospheric emissions, and chemicals such as solvents. On
industrial estates, activities are carried out on yards drained by
surface water sewers. These can discharge direct to rivers.
Pollutants are washed off impervious surfaces and can arise
through (illegal) mis-connections to sewers. These can cause
pollution by oils, hydrocarbons, pesticides, organic wastes, faecal
pathogens, nutrients, chemicals from detergents, and products used
in gardening. The use of pharmaceuticals and cosmetics has
increased the load of substances like zinc.
The use of sustainable drainage systems (often known as
sustainable urban drainage systems, or SuDS), which can contain and
partially treat runoff naturally, can help to mitigate the
pollution from runoff if well designed.
In agriculture, livestock numbers have increased, with
corresponding risks of soil erosion and contamination associated
with organic wastes. Recent changes in crops, with a push for
higher productivity, have been associated with more use of
fertilizers, and a reliance on pesticides to control weeds and
disease. Most incidents of diffuse pollution of drinking water
supplies have been attributable to agricultural sources.
Nitrate has a potential impact on health and standards have been
imposed for drinking water. The origin of 70 per cent of this
nitrogen is associated with agriculture. A threat to drinking water
standards for surface and groundwaters has lead to the designation
of Nitrate Vulnerable Zones for land draining to waters that are
non-compliant. In these zones farmers must comply with limits on
nitrate applied to land (the requirement to reduce nitrate
concentrations for drinking water incurs costs for the treatment or
blending of water supplies).
Nitrogen in coastal waters is also said to be the key risk
factor for eutrophication. Where waters are identified as
"polluted" because they show signs of eutrophication, the
contributory catchment(s) must be designated as a Nitrate
The use of organic wastes in agriculture has also raised
concerns. The main diffuse source of faecal pathogens is from
livestock, although locally significant sources include urban land,
recreation areas and domestic buildings (for example, wrong
connections, and bird roosts on roofs and lakes). These can
threaten standards for bathing waters, despite the recent big
improvements to sewerage systems. Apart from the real and perceived
risk to public health, this causes a loss of income from tourism
because of bad publicity. In addition, monitoring is expensive with
systems costing around £100,000.
There are risks from livestock of Cryptosporidium
in public water supplies. Barriers forCryptosporidium cost
£10 million for a large water treatment works.
Recreational activities such as golf, sports field management,
boating, camping and pet exercising contribute to risks from oils
and hydrocarbons, pesticides, suspended solids, faecal pathogens or
Organic solvents and pesticides are amongst the most frequently
occurring contaminants of groundwaters. The annual cost to the
water industry in the UK for treating pesticide contamination of
drinking water is significant.
Litter, oil films, anoxic sediments, and algal blooms can have
an impact on the quality of lakes and streams, and be a nuisance to
recreation. The risks of toxic algal blooms and potential exposure
to faecal pathogens impose costs in providing drinking water.
Diffuse sources of phosphorus from land surfaces come from a
range of sectors. The water industry provides a substantial input
from point sources. In areas designated as sensitive to
eutrophication because of phosphorus under the Urban Wastewater
Treatment Directive, phosphorus removal is required at large sewage
The main impacts for the water industry of eutrophication are
increased treatment costs as a result of algal blooms. These can,
in some cases, also deplete dissolved oxygen and affect fisheries
and are dangerous to livestock and domestic animals. Phosphate can
also affect plants, displacing sensitive species of high
Phosphorus is also considered to be a threat to lakes. Waterfowl
depend on good water quality for the aquatic plants and
invertebrates on which they feed.
Many costs of diffuse pollution are not borne by the polluter.
Government, industry and households pay. Impacts on agricultural or
fisheries may increase the price of our food.
Note: - CIWEM Policy Position Statements (PPS) represents the
Institution's views on issues at a particular point in time. It is
accepted that situations change as research provides new evidence.
It should be understood, therefore, that CIWEM PPS's are under
constant review, that previously held views may alter and lead to