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Agriculture's impacts on water availability. Global Food Security (GFS) and UK Water Partnership.

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Agriculture's impacts on water availability. Global Food Security (GFS) and UK Water Partnership.

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This sub-report details discussions of an interdisciplinary working group, coordinated by the Global Food Security (GFS) and the UK Water Partnership. Their work explored the tensions between water availability and food production in the UK, identifying future challenges, knowledge gaps and potential methods for easing the pressure on water resources. This report explores the tension between the availability of water and the production of food in the UK. https://www.foodsecurity.ac.uk/publications/agricultures-impacts-water-availability.pdf
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SUB REPORT
Agriculture’s impacts on
water availability
FARMING AND WATER 2
Authors
Glenn Watts (Environment Agency)*
Alan Jenkins (Centre for Ecology & Hydrology)
Tim Hess (Cranfield University)
Ann Humble (Welsh Government)
Caroline Olbert (Scottish Water)
Melvyn Kay (UK Irrigation Association)
Vicky Pope (Met Office)
Tim Stannard (G’s Fresh)
Mike Storey (Agriculture and Horticulture Development Board)
Theresa Meacham (Global Food Security programme)
Tim Benton (Global Food Security programme)
Andy Noble (BBSRC)
* Indicates Lead Author
Indicates Working Group Co-Chair
This report represents the views of the working group and not
the organisations for which they work.
Contents
Executive Summary 1
Introduction 3
How do agriculture and water interact? 4
Current and future pressures on demand and supply 8
On-farm water management 11
Large-scale management 14
Looking to the future 16
Conclusion 18
References 19
Agriculture’s impacts on water availability | 1
and flood risk and also the interaction between heat, drought and
the length of time for groundwater to recover in terms of recharge.
Efficiencies in water use need to be sought; for example in the
horticultural sector, sensors can be used to determine the irrigation
needs of covered crops.
There is currently an insufficient understanding of how agricultural
practices could be adapted to cope with changes in the weather.
There is also insufficient understanding of how the intensification
of farming methods and new ways of production impact on the
environment, by affecting water availability, both through the impact
of usage and water management.
Water for livestock
Livestock farmers use water for drinking water, washing animals,
cleaning yards and cleaning parlours. It is possible to reduce the
volume of water consumed through new housing and adopting new
production techniques. There is also scope to reduce water losses
through maintenance (e.g. fixing leaks in water troughs) and good
management (e.g. trigger sprayers when washing down) or reuse of
cooling water.
Rainwater collection may be a viable alternative water source for
livestock farms than extraction or using mains water, as many are
located in the wetter parts of the country, have large areas of have
surfaces and roofs and lower quality water can be used for washing-
down and cleaning. However, whilst this may reduce on-farm
water costs it does not create ‘new’ water and the water captured
may otherwise have contributed to streams or aquifers. Livestock
farms still require an adequate mains water supply to meet water
requirements during periods of low rainfall and drought.
Reservoirs and water transfers
Reservoirs are increasingly viewed as the best way to secure reliable
water supplies for agricultural irrigation and are the preferred
adaptation for coping with the increased risk of water scarcity. They
provide a secure water storage mechanism, because once water is in
the reservoir, the farmer can plan the following year’s cropping and
their supply contracts with supermarkets and processors with much
greater certainty. They can also improve water supply for domestic
and environmental uses by reducing abstraction during summer
months. Larger reservoirs may help to attenuate peak flows when
flows are high and maintain low flows during dry spells.
Investing in storage is always a more expensive option than direct
summer abstraction, even though summer water charges are ten
times higher than in winter. Most farmers find it difficult to justify
costs in relation to returns they expect from the investment. Most
reservoirs being built are supported by government grants in order
that they are viable financially, or they are financed as part of an
aggregate extraction package.
Water transfers are where there is an artificial movement of water
from one water body to another. They can be an effective way of
providing water for agriculture and public water supply, moving water
form an area of surplus to an area where water is scarcer. Building
Pressures on the UK Water supply
The pressure on the UK water supply is increasing, mainly due to
an expanding population, particularly in the south-east of England.
Climate change is also creating one of the main long term pressures
on water availability in the UK and is expected to intensify the
global hydrological cycle, leading to more floods and droughts on
average, though not in all regions. The pattern of change over the
21st century is not expected to be uniform, with the contrast in
precipitation between wet and dry places and wet and dry seasons
expected to increase.
The UK is generally perceived to be wet; however water availability
varies across the UK, and over time – in some places and at some
times, water availability is heavily constrained. In addition to there
being a gradient of rainfall from west to east England, there is also
an increase in the population density in the South East of England,
meaning that there is greater demand for water.
Agricultural Irrigation
Although the total volume of water used for agricultural irrigation is
small relative to other uses, irrigation potentially has a large impact
on water resources. Potatoes and other vegetables account for the
majority of water used for irrigation in England and Wales, using
25% and 54% of irrigation water respectively1. Irrigation water
use is consumptive (i.e. water is not returned to the environment
in the short term) and is concentrated in the months and years
when resources are most constrained and also the driest areas of
the country (mainly in East Anglia, South East and parts of the East
Midlands). As a result, in some dry summers, irrigation of food crops
can be the largest abstractor in some catchments.
To ensure that the expectations for food production, water use and
the environment can be met over the rest of the century, effective
management of water supplies is required. Better forecasting of
extreme weather events and how they may change over time is
needed. Better knowledge is needed concerning extreme rainfall
Executive summary
2 | Farming and Water 2
a new transfer is expensive, usually requiring extensive engineering
works over a large area. So, determining whether new transfers are
worthwhile depends on the costs and benefits of the alternative
sources of water. Research can potentially highlight the most
promising circumstances for water transfers, where benefit-to-cost
ratios are lowest. This requires better understanding future supply
and demand.
Managing water availability
Water catchments provide a range of important ecosystem services
to society as a whole, beyond simply the provision of food and water.
For example: land management for flood prevention; access to land
for recreation and leisure activity (including walking and fishing);
and habitat for biodiversity. Any change in the management of one
part of this complex system has the potential to lead to negative
impacts in other parts. As water availability changes through
both demand and supply-side drivers, such as climate change, the
potential for negative interactions to intensify may increase. Further
understanding of the wider impacts of climate change on water
availability, including a better understanding of changing catchment
hydrology, is therefore needed.
The management of the competing demands on water resources
needs to incorporate advances in thinking around public and private
policy. Flexibility and responsiveness will allow new information
and methods to be used as they are developed. Any management
aimed at addressing water quantity in agriculture needs to take into
account other requirements of the wider water system. Catchment
management approaches, where methods are used to move water
from places or times when it is not scarce to places or times when it is
scarce, can be used to achieve this.
Key findings
The main challenges were identified as: 1) allocating water
to farming, for domestic and industrial water supply, and the
environment in a way that meets the wider needs of society,
2) using water efficiently, especially in times of scarcity, and 3)
looking to the future to make sure that expectations for food
production, the environment and other water use continue to be
met over the rest of the century.
There is the potential for market failure to occur with respect to
water use. This can arise from a variety of routes. Farmers often
lack information on current and future water availability and
their possible options to manage these better. In such a complex
area, people may not fully understand or manage the risks they
face, and policies set in one area can have unexpected impacts
in other places. Finally, managing water and food production
needs a long-term view, but many of the decision-makers
inevitably have to take short term decisions about cropping
patterns and varieties. All of this suggests that more work is
needed to understand the risks and potential solutions to this
important problem, and that these must translate into practical
action that protects both food and water security.
A number of key evidence gaps exist across the catchment and
throughout the supply chain which could aid water management
on the farm. These are:
• Anincreasedunderstandingofthelinkbetweenfarming
practices and run-off at both high and low flows in order
to develop appropriate mitigation actions for water
management; this requires new research.
• Identicationofopportunitiesforsavingwateronthefarm
and new innovations to make them viable.
• Bettermanagementofthedemandforwatergeneratedby
the food supply chain, both in the UK and globally for food
imported into the UK, in order to improve water use efficiency
and reduce environmental and social issues.
• Signicantimprovementsinforecastingofshortandmedium
term water availability in order to improve water management.
• Abetterunderstandingofthewiderimpactsofclimatechange
on future water availability, including changing catchment
hydrology. This will enable better long term planning.
• Improvementsinmechanismstoallowthereallocationof
water between different uses, to the wider benefit of society.
Agriculture’s impacts on water availability | 3
1.1 This report explores the tension between the availability
of water and the production of food in the UK. The report
aims to identify the challenges, evidence gaps and potential
solutions around the linkage between water availability
and food production, with particular regard to farming and
environmental impacts. Companion reports explore the issues
around managing jointly for food and water quality, and our
sourcing of food from overseas on supply chain risks and for on
water availability in the producing countries.
1.2 In this report we start by examining the overall context of how
water and agriculture are linked and water use managed, we
then take a detailed look at agricultural use of water and the
routes by which agriculture can change its demand on water.
Finally, we look to the future and discuss knowledge needs and
potential actions.
1.3 World demand for food is expected to rise by 60-100% by
20502, driven by growing population and changing diets. The
projected 2bn extra people by 2050 is the equivalent of 250
cities with the population of London which clearly requires
significant land area for housing and urban infrastructure. At
the same time, the world is changing rapidly. For example,
changing weather patterns, particularly increasing extremes of
weather (drought, heat, and intense rain leading to floods), are
expected to undermine the ability to increase crop yields. This
impact on agriculture will vary across the world, but a globally-
linked trading system means that reduction in yields in some
places (e.g. Africa, Asia) will send economic signals to intensify
production in other places where there is potential for yield
increases (e.g. NW Europe). Thus, from the food perspective,
we can expect strong pressure on UK land for food production
increases.
1.4 In the UK, demand for water is increasing mainly because of
a growing population. The increasing economic growth, and
linked population growth, especially in the drier SE of England,
is putting growing pressure on water resources in some areas.
Industry is also a significant user of water and as consumption
of goods increases (not only manufactured goods, but also
energy) so does the demand for water supply. Increasing
weather variability, as shown by the droughts of 2010-11 and
the floods of 2013-14, indicates that we have to plan for both
increasing and decreasing water availability.
1.5 Both water supply and food production are ecosystem services
mediated by the land. There is, therefore, something of a
tension between them. Intensifying agricultural production
may impact on water availability in times of drought by
increasing the competition for a scarce resource that others
want, and may increase downstream risk in times of flooding
by accelerating flow of water from drained lands upstream.
Managing land to maximise availability of water in terms of
drought, or minimise flooding in terms of excess, may trade-off
against agricultural production potential and vice versa. This
report explores this linkage.
Introduction
4 | Farming and Water 2
Water and agriculture:
the situation now and
in the future
Water availability for agriculture
2.1 Agriculture, food production and water are inextricably
linked. On the one hand, water is an essential input for crop
production, livestock and food manufacturing. On the other, the
nature of agricultural land use affects the hydrological cycle in
terms of the partitioning of rainfall between evapotranspiration,
runoff and groundwater recharge, and the quality3 of runoff
water in terms of, for example, nutrients and sediment. Water is
used in agriculture to grow grass and crops, to support livestock
and for general on-farm use (such as cleaning, sanitation, crop
spraying). 250 million m3 y-1 of water is also used by the food
and drink industry in processing (Defra, 2007)4. Although the
UK is generally perceived to be wet, water availability varies
not only from place to place but also from time to time. Water
availability, from rivers, lakes and groundwater, is constrained
by the physical processes of rainfall and evapotranspiration.
Typically, river flows and groundwater levels are lowest towards
the end of the summer and into early autumn. However, there
are competing demands for water and judgements have to
be made on how much water should be left in the natural
environment to support wildlife, navigation and recreation.
How do agriculture and water interact?
• Rainfall is the largest source of water for growing grass and
crops in the UK. The timing of rainfall is particularly critical
to agriculture and seasonal droughts can lead to significant
reductions in crop yield.
• Abstraction is water taken from rivers, lakes or groundwater
to supplement rainfall for irrigation, for livestock and for
general on-farm use. In comparison to the others, this
latter category is very low. The volume of water abstraction
varies across the UK but is dominated by the need for
power generation and for public water supply. It has been
estimated5 that total on-farm water use in England and
Wales is in excess of 300 million m3 y-1, of which spray
irrigation is slightly under half. This contrasts with reported
abstraction for agriculture of around 120 to 150 million m3
y-1 6, demonstrating how much comes directly from rainfall.
This total of 300 million m3 y-1 represents around 1.5% of
total fresh water withdrawals in England and Wales. Water
use totals vary from year to year, but agricultural abstraction
varies from less than 0.5% of total abstraction in north-west
England to around 5% of total abstraction in the east of
England.
Agriculture’s impacts on water availability | 5
• Mostirrigation is for outdoor field scale crops, most notably
potatoes and field vegetables. The volume of water used
for irrigation varies from year to year, depending on rainfall.
In the last decade total irrigation in England and Wales has
varied from nearly 120 million m3 y-1 in 2003 and 2011 to
as little as 50 million m3 y-1 in 20127. The maximum legally
allowed for spray irrigation in England and Wales is much
higher, at over 300 million m3 y-1.
2.2 In some places, and at some times, water availability is
constrained. In general, there is less water available in the south
east as there is an appreciable gradient of rainfall from west to
east and population density (and therefore demand for water) is
highest in the south east of England. Droughts – loosely defined
as an unusual shortage of water with consequences for people
or the environment – occur across all parts of the UK (Marsh et
al. 2007)8. In the impermeable catchments of the north and
west short, intense droughts lasting 12 months or less can lead
to shortages of water. In the permeable catchments of the south
and east, it usually takes at least two consecutive dry winters
before the possible consequences of drought are serious.
The impact of low rainfall for agriculture
2.3 The 2011-12 drought in England and Wales provides a good
example of a drought’s agricultural impact. During the dry spring
of 2011, dry soils in eastern counties and the Midlands made it
difficult to prepare seed beds, and not only triggered an early
start to the irrigation season but affected the early growth of
both cereal and root crops. Livestock farmers faced higher animal
feed costs. The agricultural stress eased during the summer of
2011 but intensified through October and November resulting
in difficulty in harvesting crops. Crop yields were severely
affected particularly on light, sandy soils and shallow rooting
crops suffered particularly badly. During the early months
of 2012, with restrictions on spray irrigation expected, some
cropping patterns were revised. The irrigated crop sector faced
a difficult spring and summer with the likelihood that available
water would be exhausted before the planned harvest and an
expectation that yield and quality would be poor.
The impact of irrigation on water resources
2.4 Although the total volume of water used for agricultural
irrigation is small relative to other uses, irrigation potentially has
a large impact on water resources. Irrigation is concentrated into
a few months and uses water in the driest years when resources
are most constrained9. It is concentrated in the driest areas of
the country (mainly in East Anglia, South East and parts of the
East Midlands) and it is a consumptive use (that is, water is
not returned to the environment in the short term). As a result,
irrigation of food crops can be the largest abstractor in some
catchments in some dry summers.
2.5 Irrigation demand is highest in hot, dry summers, where
additional water makes most difference to the crop. Demand
is also higher if the added value is greater, so world food
availability and its prices play their part in influencing irrigation
demand from year to year. Farmers normally need to decide
on their planned irrigation schedule at the start of the growing
season, so changes in water availability, such as irrigation
restrictions, are unwelcome.
2.6 Rules about abstraction are also very important in determining
water availability. Typically there may be rules that stop or
restrict abstraction if river flows are below a specified level.
Water allocation rules are also important in determining how
much water is available for agriculture. Currently, abstraction is
prioritised in the order it was requested with no consideration of
how beneficial each use may be. In many parts of England and
Wales, this means that no more water is available for summer
abstraction10. Farmers can build their own reservoirs to store
winter water but this is usually an expensive option that requires
considerable investment and planning consent. On some farms,
there is no suitable location for an on-farm reservoir.
2.7 Crops that are irrigated tend to be of higher value and grown
in drier areas, where additional water makes most difference to
crop yields and quality. The three most important irrigated crop
categories (potatoes, field vegetables, and soft fruit) account
for 85% of the total volume of irrigation water abstracted
annually. The spatial distribution of agricultural holdings
involved in potato, field vegetable and soft fruit production
in 2008 has been mapped and compared against water
resource availability11. The analysis shows that on average only
10-15% of agricultural holdings are located in catchments
where additional water abstraction would be available during
summer low-flow periods. About half of all holdings are located
in catchments where no more water is available. Nearly a fifth
of holdings are in catchments where too much water is being
abstracted and measures are needed to restore environmental
flows. Therefore, in water stressed catchments, where water
demand for irrigation exceeds available surface or groundwater
water supplies, reducing the use of abstracted water would
mean that water resources could be released to sustain
environmental flows or support other uses.
Using water for livestock production
2.8 Water is required by livestock farming for drinking water, for
washing animals and for cleaning yards and parlours. The water
used for livestock has very different impacts from water used
for irrigation as it is required all year round and the prominent
livestock regions tend to be in the north and west of the country
where there is less stress on water resources. The amount of
water required for drinking depends on the size of the animal
and the diet, as a proportion of the drinking water requirement
may come from moisture in the food (especially when fresh
grass is grazed). The balance may come from natural sources
(such as ponds and streams) or be supplied by mains water in
drinking troughs.
2.9 The volume of abstracted water needed to produce meat at
the farm gate is equal to 67 l kg-1 for beef and 49 l kg-1 for
lamb12 (see ‘Water use in our food imports’ report for detailed
discussion of “embedded” water in food products). Dairy farms
also use significant amounts of water for cooling and in total it
takes about 8 litres of fresh water to produce 1 litre of milk at
the farm gate13. Although most livestock farms use mains water,
30% of water for livestock rearing is abstracted from surface
and groundwater sources14. This is discussed further in the
‘Water use in our food imports’ report.
6 | Farming and Water 2
Impact of agriculture on water availability
2.10 Abstraction of water for agriculture, reduces the availability of
water for other users and uses (public water supply, industry,
the environment). For groundwater, sustainability implies not
using more each year than the annual recharge rate while
leaving enough water to support connected water features
(wetlands and rivers); for water in rivers and aquatic systems,
environmentally sustainable water use requires not reducing
flows to an ecologically detrimental level (the concept of the
“minimum environmental flow”) and on the social side requires
sharing of water among all the stakeholders (up and down
stream, industry and domestic). Concerns have been raised over
the potential impacts of water abstraction on the environment,
particularly in catchments where irrigation abstractions are
concentrated and where water resources are under pressure.
Farming and flooding
2.11 As agriculture is the dominant land use in the UK, the
management and condition of the land surface impacts on
the generation of runoff and can contribute to, or mitigate
downstream flood risk15. Although rural land management has
changed markedly over the last 50 years, the impacts of these
practices in terms of runoff generation at the catchment scale
have been difficult to quantify. Major reviews of the scientific
literature16,17 concluded that there was substantial evidence
of changes in land use and management practices affecting
runoff generation at the local and small catchment scale, but
very limited evidence that these local changes were propagated
downstream at the larger catchment scale.
Agriculture, and the management of rural land, has important
links to flood risk in three ways:
1. As only 6% of the UK land area is urban, the management
and condition of the rural land surface largely determines
how much, and how quickly, rainfall is translated into river
flow. Creation and maintenance of land surfaces that
encourage infiltration and the temporary storage of rainfall
in the catchment can potentially reduce downstream flood
risk by smoothing out flows.
2. Flood plains perform a critical function in providing
temporary storage of flood water and riparian agricultural
land, being more resilient to flooding than properties and
infrastructure, can be used for flood storage.
3. 13% of the “best and most versatile” agricultural land in
England and Wales is at risk of flooding from rivers or the
sea, however this includes 56% of the Grade 1 agricultural
land18. Therefore a significant proportion of agricultural
production is at risk from flooding.
Agricultural land and runoff generation
2.12 When intense rain falls on agricultural land, the natural
permeability of the soil allows a proportion to infiltrate into the
soil, at least until the soil is saturated, whilst the “roughness”
of the surface serves to retain water on the land and slow
down the rate at which is reaches watercourses. This natural
function will vary according to soil type and land use, with little
infiltration occurring on clay soils but much more on sandy
soils. Loss of infiltration capacity in the catchment, such as
“surface sealing” through urbanisation, can therefore result
in more water running off the land during rainfall events and
water finding its way into watercourses more quickly. The
result is “flashier” rivers and increased flood risk downstream.
Agricultural intensification, resulting in soil compaction, removal
of hedgerows and field drainage, has increased the runoff of
rainfall from agricultural land and the Environment Agency19
have estimated that about 14% of floods in England and
Wales, mainly at the local level, are attributable to runoff from
farmland.
2.13 Studies in S W England20 have shown widespread structural
degradation of agricultural soils that has resulted in increased
Agriculture’s impacts on water availability | 7
surface-water runoff. This has been particularly associated with
late-harvested crops (such as maize) where farm traffic on wet
soil has led to soil compaction.
2.14 There are many practices that can be employed by farmers to
encourage infiltration and avoid compaction, such as; lower
stocking rates, grazing management, seasonal removal of
livestock to avoid poaching of soils, field machinery with low
ground pressure tyres, avoidance of field operations under wet
conditions, soil improvement measures including conservation
tillage, and field drainage21. Other practices can slow the rate at
which water discharges from fields into watercourses including;
reinstating field boundaries (hedges, walls and shelterbelts),
contour ploughing, artificial bunding and retention ponds.
2.15 In the Nant Pontbren catchment (mid-Wales) shelterbelts were
established in selected pastures of land used for sheep grazing.
Infiltration rates were significantly higher in areas planted
with young trees than in adjacent grazed pastures and runoff
volumes have been reduced by 50-75%22. As a result it has
been suggested23 that flood peaks in this small catchment could
be reduced by up to 20%.
2.16 Although rural land management has changed markedly
over the last 50 years (driven partly by agricultural policy),
the impacts of these practices in terms of runoff generation
at the catchment scale have been difficult to quantify. There
is a need for more evidence of the linkage between local
processes that affect runoff generation at the local and small
catchment scale (as in S W England, above), and the way they
may be propagated downstream at the larger catchment
scale24,25, because the current absence of evidence does not
necessarily imply there is no effect of land management on
catchment scale processes. Of course, detection of change
is very difficult and modelling suggests that “flood sensitive”
rural land management could be expected to make a positive
contribution to sustainable flood risk management, especially
for smaller, more frequent events26. In addition, the changes
in land management that reduce flood risk are also good for
water quality (by reducing soil erosion and sediment loads) and
may be beneficial where structural measures are too expensive
in relation to the benefits, thus offering multiple environmental
ecosystem services
Agricultural land as a flood storage area to reduce
flooding in urban areas
2.17 Flood plains are usually flat, fertile land and virtually all the
flood-plain land in the UK is farmed in some way. Traditionally,
flood plain management was dominated by uses that were
resilient to frequent flooding, such as summer grazing and grass
conservation (hay and silage). Over the years, and particularly
since the 1950s, flood plains with higher agricultural potential
have been protected from flooding and land drainage has
been improved, often with public funding, in order to enhance
its agricultural potential. The separation of the flood plain
from the river has resulted in a loss of flood storage and,
in places, increased downstream flood risk. Across Europe,
there are initiatives (e.g. along the Rhine in Germany and the
Netherlands27) to reconnect flood plains with their rivers to
restore the natural flood attenuation function.
2.18 Washlands are areas of flood-plain land that are isolated from
the river by flood banks, and are allowed to flood at peak times
in order to reduce flood risk downstream. These areas may
support agricultural land or habitats valued for biodiversity,
however, the three uses may not always be compatible and
there may be trade-offs with agricultural or biodiversity uses in
order to maximise flood attenuation28.
2.19 Most plants can withstand short periods of inundation with little
noticeable impact, particularly if flooding occurs in the winter,
when plant growth is minimal. Periods of winter flooding of
up to 21 days often have limited impact, however, prolonged
waterlogging and flooding when the plants are actively growing
leads to anoxic conditions in the root zone, slowed growth of
crops and reduced yield and/or crop quality. The severity of
the effect depends particularly on the plant type, the duration
of flooding and the time of year. In the extreme, flooding can
reduce yield to the point where it is uneconomic to harvest
and the crop is written-off. Grassland is similarly affected and
grazing-days, as well as hay and silage crops, may be lost due
to flooding necessitating additional housing and purchase
of supplementary feeds. Flooding also causes delays in farm
operations; additional costs of inputs (e.g. fertiliser); moving
and housing of animals; increased risk of animal disease (e.g.
liver fluke); clean-up and reinstatement; and damage repair.
2.20 Flooding of agricultural land may have knock-on impacts for
production. Late summer or autumn flooding may prevent
sowing of winter crops and compaction, due to unavoidable
farm traffic on wet soils and loss of soil invertebrates (such as
earthworms)29 leads to reduced yields in subsequent years.
2.21 The summer of 2007 saw flooding of 42,000 ha of farmland
across England30 with significant effects on yields and farm
incomes. The average farm level loss was estimated at £1,200/
ha, but this varied according to the type of enterprise31. Many
cereal crops recovered somewhat and average cereal yields on
flooded land were only down by 40%. Horticultural farms (e.g.
in the Vale of Evesham) suffered the greatest losses, estimated
at £6,900/ha, where crops were written off. The national
flood damage cost for the agricultural sector was estimated at
£50.7 million. Although the impact on national production was
small, the losses to individual farms were significant, averaging
£90,000 for each farm affected. Some farm losses (such as
damage to buildings and machinery) are covered by insurance,
but crop and grazing losses are not covered and many farms are
not insured.
2.22 About 5,000 ha of farm land in the Somerset Levels and
Moors were flooded in the spring of in 2012 at a time when
stock are turned out to grass or pastures are prepared for the
conservation of winter feed. Where flooding lasted for less than
2 weeks, average losses were £140/ha, but longer duration
flooding resulted in farming losses between £850/ha and
£1,120/ha as well as, serious damage to habitats and wildlife32.
8 | Farming and Water 2
Current and future pressures on demand and supply
3.1 In this section, we consider how demand for water may change
in the future and how water availability may change in the
future. We also consider the linkages that exist between both of
these factors.
Water demand is defined as the additional water from
rivers, aquifers, reservoirs and public water supply that
farmers use to supplement rainfall. Water demand is
therefore related to rainfall and other local climatic
conditions (principally temperature and windspeed as these
to a large extent control evapotranspiration losses) as well as
crop type, farming practice and soil and site characteristics.
• The absolute availability of water for irrigation is a
function of climate and other uses of water, including the
need to leave water in rivers and aquifers, to maintain the
natural environment. Farming practices and other land-uses
also influence water availability - for example by changing
soil infiltration characteristics or by encouraging rapid run-
off. Both water availability and demand vary over time; in
general, least water is available in dry summers when the
irrigation demand is also highest.
How will agricultural water demand change in the future?
3.2 In the next ten to twenty years changes in agricultural water
demand may be driven by regional food requirements, global
food markets, new crop types and varieties as well as by water
availability (which may also be influenced by demand growth
in other areas, such as the increasing population size in the SE
of England). The recent shift towards supermarkets accepting
blemished produce may lessen the value of irrigation on some
crops where water is used essentially for cosmetic reasons.
Changes in the global agri-food system and concerns around
reducing resilience in supply chains, may make it desirable to
grow more food locally, potentially increasing irrigation demand
in areas where water scarcity exists. New crops or varieties could
be more water-efficient, but equally may use the same volume
of water whilst delivering other benefits, perhaps an increase
in yield or disease-resistance, producing more food per litre of
water and becoming indirectly more water efficient.
3.3 Climate change will have an increasing impact on the demand
for water for both livestock and arable crops. With higher
summer temperatures, livestock will need more water and
it may be necessary to make provision for permanent water
supplies (cattle troughs) in places where these are not needed
now. Warmer, drier summers will increase irrigation demand
and may lead to irrigation in places where there is currently
little, or on crops like cereals that are not normally irrigated in
the UK but are irrigated in other parts of the world.
How will water availability change in the future?
3.4 At any location, average water availability for agriculture is a
function of the hydrological characteristics of the catchment,
other demands for water, and rules about how much water is
allowed to be taken. At any one time, water availability is also
determined by how much rainfall there has been.
3.5 In the future, pressures on water resources seem likely to grow,
with many areas already failing environmental objectives.
Demand for public water supply has been broadly stable for the
last decade or more, but increased population, particularly in
the south-east of England, could lead to increased demand in
some places.
3.6 Climate change is expected to intensify the hydrological cycle,
leading globally to more floods and droughts on average33,
though not in all regions. The pattern of changes over the
21st century is not expected to be uniform, with the contrast
in precipitation between wet and dry places and wet and
dry seasons expected to increase34. Rainfall over northern
hemisphere mid-latitudes increased over the 20th century35
but UK average annual rainfall has not changed significantly
since records began in the 18th century36. However, within this
unchanging average there has been a trend towards more
winter precipitation, though with little change over the last
50 years36. There is also a trend towards more intense rainfall
events37. Climate change is creating one of the main long-term
pressures on water availability in the UK.
3.7 What does this mean for water availability? Reductions in
average summer flows38 would lead to more pressure on water
resources and reduced water availability. All seasons are likely
to become warmer and heatwaves may be hotter and more
prolonged. Hotter, drier summers would be expected to lead to
increased demand for public water supply39. At the same time,
the aquatic environment may be under stress from increased
river and lake water temperature, reduced dilution of pollutants
and reduced flows40. Although we do not yet understand
possible changes in drought frequency and duration, droughts
will occur and we must continue to plan for a wide range of
possible droughts including long droughts outside recent
experience41.
The impact of land-use on water availability
3.8 The link between land-use, farming practice and the
quality of the local water environment is apparent, but
upstream measures are increasingly seen as part of the
UK’s wider response to floods and droughts. Some farming
practices increase run-off and reduce infiltration making
catchments more vulnerable to both floods and droughts.
Land management cannot prevent floods or protect from all
droughts, but sensitive management can make catchments and
society less vulnerable. For example contour ploughing can help
reduce run-off and sediment transport. Bank-side roughness –
hedges and trees, for example – slows the flow of flood water,
hence reducing the height of flood peaks. And, in times of
extreme flow, fields can be used as flood plains to protect urban
areas although this may require compensation to land-owners
and may reduce the UK’s agricultural outputs.
3.9 The link between crops, food and water availability is often
unclear to consumers and decision-makers (see ‘Water use
in our food imports report’). Embedded or virtual water – the
Agriculture’s impacts on water availability | 9
water that was used to make a product or grow a crop – is
always unclear to the end-user. Even where it is possible to
infer something about how much water may have been used,
it is not possible to tell whether this water was scarce or readily
available and how else it might have been used. In a global
food market, this is particularly difficult – for example, the UK
consumer can choose between potatoes from the UK, Egypt
and Israel and each production location has very different
water availability. The other trade-offs between productivity
and wider downstream impacts of water use are also often
opaque. For example, more intensive farming increases food
production but this may come at a cost to wildlife and flood risk.
Water management: how do we do it now?
3.10 Water resources are managed in broadly the same way across
all of the countries of the UK, although the exact details
depend on the administration. Throughout Europe, the Water
Framework Directive sets the overall vision for protection of
the water environment with the objective of making sure all
water bodies support healthy ecosystems and have good water
quality (see report on ‘Agricultures impacts on water quality’).
In achieving these objectives, water abstraction has to be
managed to maintain adequate flows throughout the year,
paying particular attention to low flows.
3.11 In the UK, all but the smallest abstractions need official
permission, usually with an abstraction licence that almost
always specifies the use or uses to which the water may be put.
The licence will normally include conditions that identify the
maximum volume of water that can be taken, often with hourly,
daily and annual limits. Abstraction may be limited to particular
months or may be allowed through the entire year. Particularly
for abstraction from surface waters, there is usually a condition
that limits or stops abstraction when flows or levels fall below
a specified point. Similar conditions may also be applied to
groundwater abstractions.
3.12 If someone wants to abstract water, they have to apply for
a licence. At present, all UK abstraction licensing authorities
operate on a “first come, first served” basis; in other words, a
licence will be granted based on the availability of water at that
location now, and without considering future uses of water or
whether the proposed use of water is in some way better than
existing uses. If no water is available, the licence will be refused.
Once a licence is granted, the holder has a protected right to
water that means further licences cannot be granted if they
would reduce water availability to the licence holder.
3.13 In England, agricultural spray irrigation abstraction can be
restricted or stopped by the Environment Agency during
droughts; in practice, the Environment Agency seeks
voluntary reductions in water use wherever possible. Natural
Resources Wales has the same powers in Wales. The Scottish
Environmental Protection Agency, SEPA, also has the power to
alter licences to protect the environment.
Since privatisation and as a result of the outcome of extensive
environmental assessments, Anglian Water has made
significant investment to help understand and minimise
the impacts of their abstractions. As a result, Anglian Water
have reduced output from, relocated or closed a number of
abstraction sources. Anglian Water currently operate 15 river
support schemes, of which 12 are directly associated with
one of their abstraction licences. The river support schemes
comprise boreholes that are pumped to enhance flows and
river ecology at times of environmental stress, or as advised by
the EA.
In addition to these existing mitigation measures, a significant
proportion of abstraction licences include conditions requiring
them to monitor environmental impact which they report
on annually. If the results of this monitoring indicate any
deterioration, then they remain committed to addressing the
issue.
BOX 1: Case Study: Environmental impact of
abstraction: Anglian Water
Glen Watts
10 | Farming and Water 2
The river Wye is one of the largest rivers in Britain, rising in the
Pumlumon mountains of mid-Wales and flowing down through
the Wales – England border before meeting the Severn estuary at
Chepstow. The total catchment area is 4136km2 and the river’s
mean annual discharge is 80 m3 per second. Although the river
has a large catchment, the geology means that there is little or no
groundwater storage and as a result the river is very responsive to
rainfall and drought.
It is designated as a European Special Area of Conservation
(SAC) (underpinned by Site of special scientific interest (SSSI)
designation) for 6 species of fish, including Atlantic salmon, white
clawed crayfish and Eurasian otter. One of the most striking
features is the series of dams in the Elan valley catchment
that allows the transfer of water via a gravity fed aqueduct
to Birmingham and the regulation of flows in the river Wye.
Regulation of the river Wye is undertaken through a management
agreement between Dŵr Cymru Welsh water (DCWW) and Natural
Resources Wales (NRW).
The environmental vision for the river system is that ‘all of
its special fish and other animal features are able to sustain
themselves in the long-term as part of a naturally functioning
ecosystem. Allowing the natural processes of erosion and
deposition to operate without undue interference and maintaining
or restoring connectivity maintains the physical river habitat, which
forms the foundation for this ecosystem.’ Abstract from the Wye
River / Afon Gwy SAC site management plan 2007.
The water flow from the Elan valley dam system has a number
of impacts on the environmental functionality of the river.
Compensation water released from the reservoir can often be
colder than normal river temperature and have lower oxygen levels
and this can detrimentally affect fish. This amount of control also
restricts the number of high flow events, which in turn impacts
on the renewal of sediment and gravel which fish species use for
spawning, although the impoundment of the water does allow
for water to continue entering the river system even at low flow.
However, the degree of river control is necessary to smooth out the
river flow and secure reliability of public drinking water.
In addition to the water companies there are a number of private
and industrial license holders who abstract water to meet their
needs. Many of the private license holders are agricultural, using
the water for spray irrigation of crops such as potatoes and fruit
growing. These licences only tend to be activated in average and
dry years impacting the river at the time of lowest flow. In the
Wye, these licenses have a clause which means that abstraction for
irrigation purposes must stop if river levels fall below a certain level
to protect public drinking water supplies.
NRW are responsible for the protection of the SAC and are
responsible for operating the water abstraction licencing system.
They are tasked with balancing the aims of SAC designation
to ‘restore the river to high ecological status’ and the Water
Framework Directive (WFD) targets to maintain the river system in
‘good ecological status’ with the demands of all the abstractors
from the river system. This balancing act requires negotiation with
Dwr Cymru who manages the dam system to ensure the discharges
support the river system and the demands of the abstraction sites
further downstream. This is achieved by modelling the demand
on the reservoirs along with the range of weather conditions
that impact on how quickly the reservoirs refill to ensure that the
reservoirs always have sufficient supplies to meet the demands
placed upon them. Agricultural needs are not included in the water
demand calculations for dam releases, which means that NRW
need to notify irrigation licence holders if there is a risk that they
may have to cease abstracting. The unpredictable rainfall in the
catchment and the responsiveness of the river mean that some
overnight rainfall may change the situation. NRW have developed
a ‘spray line’ hotline that notifies farmers and other users quickly
and immediately of any changes in water availability.
Modelling and balancing the demands of water supply on such a
responsive river system will become more challenging as climate
change makes weather events more extreme and uncertain.
Dŵr Cymru Welsh Water
BOX 2: Case Study: Balancing water supply demands
for agriculture and domestic and environment needs on
the Wye River
Agriculture’s impacts on water availability | 11
On-farm water management
Storing water supplies
4.1 Reservoirs are increasingly viewed as the best way to secure
reliable water supplies for agricultural irrigation and are the
preferred adaptation for coping with increasing water scarcity.
Storage is one of three key themes which make up agriculture’s
strategy for ensuring a fair share of water for food production.
These include working together to improve dialogue between
farmers, the agri-food industry and regulators developing a
knowledge base to improve water management and making
best use of available water resources42.
4.2 Reservoirs are a secure water storage mechanism; once water
is in the reservoir the farmer can plan the following year’s
cropping and their supply contracts with supermarkets and
processors with much greater certainty. Reservoirs can also
enhance ecosystem services. They can secure agricultural
production and improve water supply for domestic and
environmental uses by reducing abstraction during summer
months. Larger reservoirs may help to attenuate peak flows
when flows are high and maintain low flows during dry spells,
so long as they are not full or at a low level. They also provide
informal recreation, nature conservation, and indirectly support
rural employment along the agricultural value chain43.
4.3 Most reservoirs are either constructed in clay or clay lined, but
some have a synthetic membrane lining to control seepage and
are usually much smaller capacity. Costs vary by size and type
(clay and membrane lined) and also include ancillary works
such as inlets, pump stations, and pipework. A recent reservoir
review showed that the unit cost (in £/m3) of membrane lined
reservoirs is almost three times the cost of clay reservoirs44.
Storage capacity provides a good indicator of capital costs
provided a distinction is made between the linings.
4.4 Investing in storage is always a more expensive option than
direct summer abstraction, even though summer water charges
are ten times higher than in winter. The additional reservoir
costs can be seen as insurance against unreliable, insecure
summer water. High costs will no doubt serve to focus future
irrigation development on high-value, water responsive crops
such as potatoes, soft fruit, vegetables, and salad crops, which
can carry the additional costs of water storage45.
4.5 There are few reliable data on the number or total volume
of on-farm irrigation reservoirs. Estimates suggest that
current storage capacity is more than 20 million m3, based
on the highest recorded winter abstraction volume46. But
winter abstraction has increased in recent years. Also winter
abstraction licence numbers are increasing annually as is the
total licenced volume for storage. This reflects a trend towards
larger licences and larger reservoirs. The size of lined reservoirs
has not increased but costs have risen by 50% reflecting the
rising costs of oil-based lining materials47.
4.6 Farmers face many problems in building reservoirs. By far the
most important is the high initial cost of construction which
varies depending on size, water source, construction method,
local geology, topography, and proximity to environmentally
sensitive areas. Most farmers find it difficult to justify costs in
relation to returns they expect from the investment. Reservoirs
continue to be built, but most are supported by government
grants in order to be financially viable, or they are financed as
part of an aggregate extraction package. Farmers also face
considerable obstacles and long delays with local authority
planning and demanding environmental and archaeological
surveys which are required by different organisations.
Managing the demand for water
Livestock
4.7 Dairy, beef and sheep farmers can improve their water use
efficiency directly by better use of water, and indirectly by
Innovation in on-farm
water storage and use
12 | Farming and Water 2
improving performance efficiency. For grazing livestock,
improving grass sward management improves utilisation of
rain-onto-soil water flows – with good conditions for grass
growth (e.g. soil nutrition, soil structure, grazing management),
the grass has evolved to utilise water efficiently, so less is lost
through evapotranspiration or runoff. Soil management to
improve sward resilience with organic matter and compaction
remediation improves soil water storage48,49, while minimising
runoff and waterlogging. The efficiency of using abstracted
water can be improved with leak repair and rainwater
harvesting in high rainfall areas. With dairy, continuing
efficiencies are being implemented for washing down and milk
cooling, high pressure low volume hoses, and recycling milk
cooling water.
4.8 Enhancing genetics, health, nutrition and breeding can all
indirectly help to produce more litres of milk or kilograms of
meat per livestock unit or hectare, thereby reducing the water
requirement. Feed budgeting and reducing feed wastage
optimises feed usage to achieve target performance gains while
reducing the water embedded in livestock feed.
4.9 Deep rooting grass varieties and other forage crops (e.g.
lucerne and chicory) have been developed to enhance drought
tolerance50 while, in some cases, simultaneously improving soil
structure for water infiltration and storage. Using co-products,
such as distillers’ grains, spreads the water cost over multiple
products thereby reducing the water footprint to the livestock
producer. Livestock genetics and breeds from drier climates
offer potential to improve drought tolerance in the UK beef and
sheep industry as the climate changes.
4.10 For non-ruminant systems, particularly pigs, the industry
consists predominately of housed production systems51, and
all production relies on sufficient, good quality piped water.
Using potable standard water is the norm, because the main
uses are for drinking and hygiene purposes52. The quality of
water is important, because animal health and performance
are interlinked53, as bacteria and disease can be passed
very quickly around herds. In recent years the emphasis on
hygiene, especially cleaning and the disinfection of houses
and equipment, has made the sector heavily dependent upon
adequate and reliable supplies of water, but at the same
productivity has risen54.There is a balance between increased
water use and better performance in relation to the amount of
feed used (embedded water), generally it is preferable to use
water than to let health deteriorate.
4.11 The cost of water is a significant driver for optimising use.
Genetic and other on-farm performance improvements are
leading to increasing numbers of pigs reared per sow and these
additional pigs increase the demand for water of the national
herd but, overall water use may decline on a unit output
(mass) basis. New housing and production techniques can
contribute to reducing the volume of water consumed. Better
ventilation and insulation optimise the housed environment,
feed consumption is focused on production, minimising
heat weather feed intake dips, and enabling the pigs natural
differentiated lying and dunging behaviour results in cleaner,
healthier pigs and pens. Modern building materials with their
impervious easy to clean surfaces reduce water required for
washing55. The health and cleanliness benefits follow the
pig through to the abattoir and water required there and for
subsequent processing.
Cereals and Oilseeds
4.12 Cereals and oilseeds production in the UK is among the most
efficient in the world, with a water footprint per tonne of
wheat of less than a third of the global averag56. However
this reflects the fact that they are largely rain-fed crops, and
typically less than 0.3% of the cereal area receives irrigation.
In future, the expected increase in rainfall variability may
increase the demand for irrigation57. Potentially, average yields
of 15 t ha-1 are possible if the crops are grown under optimal
conditions in the UK58. Better water use can be achieved by
breeding varieties with improved water stress resilience and
higher nutrient/water use efficiency. Increasing the genetic
diversity can be achieved through conventional cross-breeding
and early trials have also shown that synthetic crosses can
increase yield potential while also introducing new genetic
diversity which can be used to increase drought tolerance,
disease resistance and input use efficiency
Increasing efficiencies in horticulture and crop
production
4.13 Potatoes and other vegetables use the majority of water
abstracted for irrigation in England & Wales, accounting for
54% and 26% respectively in 2010 (Figure 1)59. Horticulture
can achieve efficiencies in water use in a number of ways.
There is already a move toward deficit irrigation using sensitive
and accurate sensors to determine the irrigation needs of
covered crops such as substrate grown strawberries. This has
potential to be used in other crops, such as tree fruit, and
over much wider areas but is currently constrained by cost.
However, if water becomes more expensive the investment
may become worthwhile. Additional efficiency can be achieved
by the selection of drought and/or waterlogging tolerant
varieties through genomics, marker assisted breeding and
other techniques; recent work in Israel has produced lettuce
that is significantly more tolerant of drought and has longer
shelf life.
4.14 For orchards, cropping plans can cover 25 to 30 year periods
so the selection of appropriate varieties or perhaps species is
something that may need to be considered very soon where
orchards are due to be replaced
4.15 The cost of water to producers and competing demands
of other users are significant drivers to improve efficiency
of water use and irrigation in potato production. In the UK,
production is from both rain-fed and irrigated systems and
the national crop uses water effectively for food production
in comparison to other dietary carbohydrates (pasta and rice)
(see ‘Water use in our food imports’ report). Approximately
50% of the production area currently has the potential to
be irrigated, but improvements in the efficiency of water use
and irrigation management will be necessary to maintain
production at current levels in the future given likely limits on
abstraction (see Box 3).
Agriculture’s impacts on water availability | 13
Figure 1: Irrigation volumes in England and Wales (%) in 2005 and 2010.
2005 2010
Main crop potatoes
Vegetables
Early potatoes
Other outdoor crops
Sugar beet
Small fruit
Cereals
Grass
Orchard fruit
Source: Irrigation Survey
49
27
7
5
4
3221
48
26
6
5
4
2
5
31
Models60 suggest that in the future, land availability suited for rain-
fed potato production will decline between 74-95% under median
UK Climate Projections 2009 (UKCP09) projections for low – high
emission scenarios due to increased drought likeliness (Figure 2).
In contrast, on land where irrigated potato production is presently
situated, this would remain suitable if irrigation water can continue
to be made available. However, without adaptation existing
irrigation schemes could have insufficient capacity to meet future
irrigation needs, with serious consequences for national yield,
quality and food supply. The uncertainty in weather patterns and
likelihood of damaging drought is driving adaptive change in crop
and soil management.
Figure 2: Projected Changes in land suitability for potato production62.
Some potato varieties are very sensitive to drought but there are
also opportunities to manage variety selection to match crop
development to water availability. As with cereals and horticultural
crops, efficient breeding of varieties with improved water use
efficiency can be aided by a better understanding of the crop’s
physiology, canopy development and rooting, and exploiting
knowledge from genomics, with the identification of markers. Crop
performance has to go hand in hand with annual soil cultivations
and improving soil structure over a number of years so that the
crop being grown can most effectively exploit the available soil
water and deliver ‘more crop per drop’. To deliver this there needs
to be a better understanding of the heterogeneity of soils and the
ability to match the crop needs with irrigation61.
BOX 3: Case Study: Increasing efficiencies in potato production
14 | Farming and Water 2
Recycling Water
4.16 As most of the water for livestock is required for their drinking,
there is little opportunity to reduce water consumption.
However, there is scope to reduce water losses through
maintenance (e.g. fixing leaks in water troughs) and good
management (e.g. trigger sprayers when washing down); or
reuse of cooling water.
4.17 Rain water collection may be a viable alternative water source
for livestock farms as many farms are located in the wetter parts
of the country; have large areas of hard surfaces and roofs; and
can use the lower quality water for washing-down and cleaning.
However, whilst this may reduce farm water costs it does not
create “new” water and the water captured may otherwise have
contributed to streams or aquifers. In addition, livestock farms
will still require an adequate mains supply to meet their water
requirements during periods of low rainfall and drought.
Large-scale water management
Water transfers: are they a solution to local scarcity?
5.1 A water transfer can be defined as an artificial movement of
water from one water body to another. Considered like this, a
transfer has three basic components: a source, a vector, and a
receptor. The source may be a river or stream, a lake, a reservoir
or groundwater. The vector may be one or more of: a canal (an
artificially constructed channel), a pipeline, an aqueduct, an
existing river channel, or road or rail tankers. The receptor may
be a water supply system, a reservoir, or direct use from the
vector – for example, direct abstraction for irrigation.
5.2 Water transfers can be an effective way of providing water for
agriculture and public water supply, with the particular benefit
of moving water from an area of surplus to an area where
water is scarcer. This scarcity may be permanent – moving
water from wetter to drier areas – or temporary, where the
receiving area may be in a more intense drought than the water
source. Transfers themselves can be temporary or permanent,
solving short-term shortages or contributing to a long-term plan
to manage water resources.
5.3 There are many existing water transfers in the UK, including:
• Trent-Witham-Ancholme:usingcanalsandriverchannelsto
move water from the Trent to two rivers in Lincolnshire, for
public water supply and agricultural use.
• ElyOuse-EssexTransferScheme:usingrivers,channels,
tunnels and pipes to transfer water from the Ely Ouse in
Norfolk to Essex rivers and reservoirs, for public water supply
and agricultural use.
• ElanValley-Birmingham:usingpipestotakewaterfrom
Wales to Birmingham for public water supply.
• RiverSevern-GloucesterandSharpnessCanal-Bristol:usedfor
public water supply in Bristol.
• Wimbleball-RiverExe:usingtheRiverExetotransferwaterto
Exeter for public water supply.
• Roadorrailtankershavebeenusedasanemergencysupply
during brief periods of drought (e.g. in 1995 tankers were
used so deliver water to reservoirs in West Yorkshire) or
infrastructure failure (e.g. when the floods in the summer
of 2007 disabled the Mythe Water Treatment works in
Tewkesbury).
Glen Watts
Agriculture’s impacts on water availability | 15
5.4 Water transfers are not without problems. They can be
controversial, because the impacts tend to fall on people who
do not benefit directly from the scheme. Removing water
from the source will deplete flows in some way, often with
some environmental impact. Putting water into a natural or
semi-natural channel leads to a risk of transferring invasive or
non-native plants and animals, as well as diseases that affect
not only the aquatic ecosystem but also crops or livestock.
Differences in water quality and water temperature can be
important, with potential for altering the characteristics of the
receiving water body.
5.5 Building a new transfer is expensive, usually requiring extensive
engineering works over a large area. In most transfers there will
be some need for pumping, and as water is heavy, the energy
use can be large. Whether transfers are worthwhile depends on
the costs and benefits of alternative sources of water, the value
of the use of the transferred water and the reliability of the
transfer itself.
Allocating water to agriculture whilst preserving other
ecosystem services: the need for catchment management
5.6 Water catchments provide a range of important ecosystem
services to society as a whole: not just water to grow food
and potentially mitigate flood risks, but also services such as
providing fresh water for drinking, raw water for use in industry
including food processing, energy production, amenity in urban
environments, leisure activity destinations, tourist attractions
and habitat for biodiversity.
5.7 Any management aimed at addressing water quantity in
agriculture, either by managing run-off or by water storage,
needs to take into account other requirements of the water
system. This will have to be considered on a catchment by
catchment basis as demands on the water resources are
location specific.
5.8 With complex systems, any change in the behaviour of one part
can work through a variety of routes to affect outcomes. When
thinking about change it is best to think about the system as
a whole to avoid the potential for negative, indirect impacts:
this is “systems thinking”. Thus, it is perhaps necessary to think
about the demand for water by farmers, industry, domestic
use and environmental needs in the round and recognise that
demand, requirement and availability are all time-varying.
Understanding how the availability of water supply is likely
to change in future (through changing patterns of rainfall),
the resilience of aquatic systems to minimum flow and how
to negotiate human use, from the different stakeholder
communities in an equitable and transparent way, will be
increasingly challenging. To what extent should a farmer be
able to abstract water to prevent significant financial losses,
if it reduces water availability for domestic users, which may
be inconvenient for domestic users but no more? Likewise, is a
short-term unsustainable use of water (causing rivers to run dry)
considered a high impact event for a short time period (in terms
of wildlife loss) even if, in the long-run, it may be low-impact if
the ecological system recovers quickly? In the other extreme,
it may be desirable to use agricultural land (with its impact on
food production) for flood water storage, upstream of large
River catchment partnerships are springing up across the UK
and these groups have been very diverse, reflecting the diverse
nature of water users. These partnerships have primarily been
looking at water quality, however, flood and drought issues are
being addressed in some catchments where water quantity
has been an issue. The Pont Bren farmer group in Powys is a
high profile example of a river catchment partnership. The
group undertook tree planting in strategic parts of their farms
to increase interception rates of rainfall and to lower the peak
flow from their catchment63. This group are aiming to expand
their approach throughout the Wye and Usk catchments.
BOX 4: Case Study: The Pont Bren Farmer Group,
Powys
settlements. Where balances need to be struck, the impacts on
all users in the catchment should be considered.
5.9 Finding ways to allocate water resources, taking into account all
stakeholders’ interests, and environmental concerns, is likely to
be a growing challenge. Catchment management approaches
where stakeholder representatives negotiate amongst
themselves for access to resources and for payment for
ecosystem services (or for water use foregone) is an emerging
approach. These types of trade-offs need to be managed
impartially or through regulation, as there is a real potential
for societal inequalities to be exacerbated. Big industry, with
large amounts of money may be able buy a larger share of
the resources at the expense of others. For instance, if water
charging was used as a tool to reduce domestic use, this has
the potential to impact the lowest income families the hardest.
Furthermore, other ecosystem services provided by river
catchments do not necessarily have the ‘buying’ power of other
users, such as biodiversity.
5.10 A balance must be struck with often competing demands
on water resources and the extremes of availability. Plans
need to consider all aspects of the system to ensure solutions
are sustainable for all members of society in the long term.
Furthermore, with multiple interests in water also come
greater opportunities to develop multidimensional solutions.
For instance, greater water storage requirements could be
coupled with leisure or tourist activities to benefit society in a
broader way.
16 | Farming and Water 2
Looking to the future
6.1 Patterns of water use and legislative controls have developed
over the last two centuries in response to needs to improve
public health, produce food and protect the environment.
With a growing population, changing world food markets
and a changing climate, pressures on UK water resources are
increasing. Here we look at the challenges of managing water
for food production and ways that this could be improved over
the coming decades.
6.2 Demand and availability change from day to day with the
weather. Demand follows a seasonal pattern with most
water needed in summer and least in winter. Availability also
follows seasonal patterns with most water available in winter
and spring and least in summer and autumn, particularly in
groundwater-fed catchments. River flows and groundwater
levels are usually lowest in late summer and early autumn.
Demand changes from year to year, as farmers grow different
crops or varieties or take different decisions about how much
irrigation to use in different years. Over longer timescales,
climate change will alter catchment hydrological response and
the crops that can be grown. Superimposed on all of these
are changes in regional and global food needs changing the
profitability of different crops and therefore demand for water,
particularly if more irrigated crops are grown in the UK. Other
uses of water will also change, and changes in the rules about
the total volume of water available for abstraction in different
places can also be expected.
6.3 Improved forecasting of water availability offers the prospect
of a more dynamic allocation of water, as well as allowing
farmers to plan cropping patterns and water application.
Hydrological forecasting in the UK has changed dramatically in
recent years, with improved short-term flood forecasting and
the development of a monthly hydrological outlook that looks
up to two years ahead64. The UK Climate Projections 2009
(UKCP0965) provide a risk-based assessment of how climate
may change over the 21st century. Further improvements in
forecasting are expected to come from improved monthly to
decadal weather forecasts, where skill is increasing as high
resolution weather models start to capture the main drivers of
seasonal variability in European weather. The UK’s position on
the edge of the European continent means that medium range
weather forecasts will always be uncertain, but improvements
should be beneficial to all water users.
6.4 Alternative approaches to water allocation may also present
opportunities for improvement. Options include:
• Centralisedplanningofwaterallocationanduse
• Localco-operativeplanningofwateruse
• Market-basedsolutionstowaterallocation,includingwater
trading
6.5 Centralised planning, usually at the catchment or river-basin
scale, can be a very effective way of managing water allocation.
It allows for a direct link between water policy and allocation,
Agriculture’s impacts on water availability | 17
which can include complex allocation rules that take into
account social and economic needs. The stability of centralised
planning can be very welcome, particularly for small businesses
with little resilience. However, this very stability means that
centralised planning is not very flexible, and it can be hard for
new water users to access water this way.
6.6 Local, co-operative planning can help to move away from the
conservatism of centralised planning towards more dynamic
planning based on local needs. Carried out well, local groups can
negotiate complex water needs in ways that centralised rule-
based planning could never achieve. However, local planning
is not always co-operative, and sometimes a few groups or
individuals achieve disproportionate influence in the decision-
making process. Co-operative planning of water use has worked
well where there are obviously shared resources, such as shared
aquifer units or where there are small internal drainage boards.
In these cases, water used by one farmer directly affects the
amount available for others. Such groups have often proved
very successful at negotiating more equable water allocation,
offering a powerful but considered voice for abstractors.
6.7 An alternative approach lets the market allocate water, most
simply to whoever will pay most for it. The market can be used
to decide on long-term water allocation, on day-to-day or
season-to-season water use, or even both. For example, in the
Murray-Darling basin in Australia it is possible for farmers to sell
their share of the resource permanently to another farmer, or to
sell water for all or part of a season. Market-based solutions can
be very flexible but this means that it can also be very difficult
to enforce agreements. In any market there is a risk of abuse,
where dominant players can exclude others from the market
or control prices in a way that makes it hard for new or smaller
users. Most markets require some sort of central management,
for example to set the basic rules for total water availability. In
the case of agricultural water use, it may be necessary to limit
trade between sectors so that water is not gradually moved
away from agriculture to public water supply.
6.8 Perhaps the most promising way of managing water availability
is through improved catchment management, sometimes
called “water cycle management”. Managing the water cycle
involves finding ways to move water from places or times where
it is not scarce to places or times when it is scarce. Reservoirs
store winter water for use in summer; in many countries, large
reservoirs are important sources of water for agriculture, but
in the UK most farm reservoirs are small. Building more farm
reservoirs can also make more summer flows available for other
summer demands and so benefit others and not just farmers.
Transfers from wetter catchments and groundwater storage
schemes can also benefit agriculture. The way the catchment is
managed also affects water availability; impermeable surfaces
create rapid runoff, but well managed soils retain moisture and
increase water availability during drier periods.
6.9 Along with all of these measures we can expect drives towards
more efficient use of water in both arable and livestock
farming. New technology can help with precision irrigation,
where exactly the right volume of water is applied. Different
crop types can use less water. Rainwater harvesting, recycling
and attention to supply system maintenance can reduce water
use in livestock farming. Away from the farm itself, supply
chain management can also reduce crop water use. For
example, supermarkets could decide to accept potatoes with
skin blemishes which would in turn reduce water use or allow
existing irrigation volumes to water more crops.
18 | Farming and Water 2
7.1 Water and food are inextricably linked: almost all of our water
flows from agricultural land, and farmers need water to produce
food. Across the UK, water resources are under pressure from
current and future demand for water as well as climate change.
At the same time, world demand for food is increasing and this
makes efficient home production more and more important. In
this report, we set out to establish the challenges, evidence gaps
and potential solutions for the linked areas of water and food.
Here we bring this together and draw our conclusions.
There are many challenges, but these can perhaps be
summarised into three main areas:
• Allocatingwatertofarming,publicwatersupplyandthe
environment in a way that meets the wider needs of society
• Usingwaterefciently,especiallyintimesofscarcity
• Lookingtothefuturetomakesurethatexpectationsfor
food production, other water use and the environment
continue to be met over the rest of the century.
Conclusions
7.2 Much is known about the links between farming and water, but
evidence gaps remain. Key evidence gaps highlighted in this
report are:
• Anincreasedunderstandingofthelinkbetweenfarming
practices and run-off both at high and low flows in order
to develop appropriate mitigation actions for water
management - this requires new research.
• Identicationofopportunitiesforsavingwateronthefarm
and innovations created to make them viable.
• Bettermanagementofwaterdemandinthefoodsupply
chain both in the UK and globally (for food imported into
the UK), in order to improve water use efficiency and reduce
environmental and social issues.
• Betterforecastingofshortandmediumtermwater
availability that is of benefit to agricultural users is needed.
• Betterunderstandingofthewiderimpactsofclimate
change on future water availability, including a better
understanding of changing catchment hydrology.
• Improvementofmechanismstoallowthereallocationof
water between different uses to the wider benefit of society.
7.3 Many of the components of potential solutions are
understood. We know that further water efficiency can deliver
many benefits, and that soil and landscape management
could deliver wider benefits as well as improving crop yield.
Dynamic approaches to negotiating and managing water
use, particularly in dry periods, could allow a better focus on
achieving the results that society wants. Is further intervention
needed, or will all of these factors come together autonomously
as pressures on water increase?
7.4 One way of looking at this question is to consider whether there
has or could be a market failure. Market failures can occur for a
number of reasons66:
• Lackofinformation-whereparticipantsdonothaveenough
information to make appropriate choices.
• Moralhazard-loosely,theideathatsomeoneelsewill
manage the risk if something goes wrong.
• Policyfailures-wherepolicieshaveunexpectedknock-on
effects.
• Governancefailure-wherethoseinchargeofdecisionsmay
not think at the right scale.
7.5 It seems clear that all of these could apply in some part to
water and agriculture. Farmers often lack information on
current and future water availability and their possible options
to manage these better. In such a complex area, people may
not fully understand or manage the risks they face, and policies
set in one area can have unexpected impacts in other places.
Finally, managing water and food production needs a long-term
view, but many of the decision-makers inevitably have to take
short term decisions about cropping patterns and varieties. All
of this suggests that more work is needed to understand the
risks and potential solutions to this important problem, and that
these must translate into practical action that protects both
food and water security.
Agriculture’s impacts on water availability | 19
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Available related reports
Global Food Security (GFS) is a multi-agency programme
bringing together the main UK funders of research and
training relating to food. GFS publications provide balanced
analysis of food security issues on the basis of current
evidence, for use by policy-makers and practitioners.
The UK Water Partnership, launched in February 2015,
brings people and organisations together to address the
key challenges facing the water sector, and catalyse action
to benefit the UK economy and improve UK and global
water security.
For further information please visit:
www.theukwaterpartnership.org
www.foodsecurity.ac.uk
Email: info@foodsecurity.ac.uk
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