HydrologicalSciences-Joumal-des Sciences Hydrologiques, 42(4) August 1997
451
Society's interaction with the water cycle:
a conceptual framework for a more holistic
approach
M. FALKENMARK
Natural Science Research Council, Box 7142, S-103 87 Stockholm, Sweden
Abstract This paper takes as its starting point today's paradoxical situation where a
global water crisis is threatening a world in which water illiteracy is widespread
among those expected to cope with that crisis. This creates a huge communication
challenge for hydrologists, having to brief decision makers, diplomats and politicians
in a manner that is simplistic without being water-reductionistic. The paper proposes
some simple explanatory models, to be used for explaining and visualizing fundamental man/water interactions. It also discusses environmental sustainability criteria
and their consequences in terms of the capacity to support water dependent
populations. Large stress is put on land/water interactions. The paper ends with a
conceptual framework based on the water cycle, distinguishing between rural and
urban water use, water structures for mobilizing water for such uses, side effects,
and key points for societal control mechanisms.
L'interaction de la société et du cycle hydrologique: un cadre
conceptuel pour une approche globale
Résumé Le point de départ de cet article est la situation paradoxale qui règne
aujourd'hui où, alors qu'une crise globale de l'eau menace le monde, les personnes
chargées de gérer la crise sont, pour la plupart, ignorantes des problèmes de l'eau.
Ceci crée pour les hydrologues un immense défi de communication, car ils doivent
éclairer de manière simple sans être hydrologiquement simpliste des décideurs, des
diplomates et des politiciens. Cet article propose quelques modèles explicatifs
simples, utilisables pour illustrer et expliquer les interactions fondamentales entre
l'Homme et l'Eau. Il s'intéresse aussi aux critères de durabilité de l'aménagement de
l'environnement et de ce qu'ils impliquent en termes de soutien aux populations
concernées. L'article se termine par la présentation d'un cadre conceptuel fondé sur
le cycle de l'eau, distinguant les utilisations urbaine et rurale de l'eau, prenant en
compte les aménagements nécessaires à la mobilisation de l'eau pour ces utilisations
et leurs effets secondaires, et mettant en évidence les points sensibles de leur impact
social.
INTERDISCIPLINARY CHALLENGES GENERATE CONCEPTUAL
PROBLEMS
New communication challenge now confronting hydrologists
Evidently, the future cannot be approached backwards by relying on the one-thing-ata-time approaches of the past. In order to find out how to proceed, backcasting from
a sustainable future would be more interesting than forecasting from an unsustainable
present. The development of images of desirable futures, however, calls for a more
holistic approach, and will be critically dependent on a conceptual human-ecological
Open for discussion until 1 February 1998
452
M. Falkenmark
framework. On the one hand separate components have to be tied together. On the
other, mankind's genuine resource dependence has to be properly acknowledged
together with the non-negotiable integrity and continuity of the water cycle processes
(Falkenmark & Steen, 1995).
The world population is presently growing by some 90 million each year,
thereby expanding the number of individuals and, as a consequence, the global food
needs. The growth is most rapid in those regions where water is scarce for
hydroclimatic reasons. Those are also the regions hosting the lowest income
countries. The effect of such driving forces is a world heading for a global water
crisis. Even if the crises will be of a regional nature, their implications may rapidly
become global (ECOSOC, 1997). Fundamental water-related questions are now
emerging. In which regions is there water enough to allow food self-sufficiency—a
strategic goal of many Third World politicians? Where this is not so, where should
the food come from? Is the world heading for a doubling of the current volume of
food trade by 2025, as the optimists think, or a quadrupling in line with the
pessimists' views (McCalla, 1994)? At the same time, water demands and waste
loads in developing regions tend to increase much more rapidly than water scientists'
capability to provide well informed answers to questions raised. The strategic dimensions of the water crisis are now generating interest also in Foreign Offices around
the world. As a consequence, politicians are moving into the area and have to be
briefed. In view of the fundamental character of the water cycle as the bloodstream
of the biosphere, hydrology constitutes a key discipline as regards world environmental problems. Target groups include scholars from other disciplines as well as
environmental activists, politicians and diplomats.
Those in charge of water management problems have increasingly realized that
the old sector-oriented agenda is creating more problems than it solves (Serageldin,
1995). From the political side, the need for a new water resources agenda is being
increasingly voiced in the international community. The focus of the old agenda has
been on the flow of water through the urban system and in particular on activities
within the International Drinking Water Supply and Sanitation Decade. The
launching of the Global Water Partnership could be seen as a first step in the new
direction. Its task is to ensure that sectorally oriented water projects do fit into an
integrated approach.
Some misconceptions and paradoxes
In spite of early warnings regarding water availability as a constraint to development,
water issues still tend to be seen as mainly technical problems. In discussions of the
development of rainfed agriculture, water is often taken more or less for granted and
the focus is put on agricultural chemicals, breeding etc. Many water generalists
complain about widespread water illiteracy, originating from the situation in the
temperate zone, generally well endowed with water (Falkenmark & Lundqvist,
1995). In environmental politics, land and water issues are still seen as belonging to
different worlds, taken care of by different professions with distinctly different
Society 's interaction with the water cycle
453
educational and professional cultures. In the process leading up to the UN
Conference on Environment and Development, for instance, land and water issues
were analysed by different working groups. Predictably, the result was that water is
largely neglected in the land chapters of Agenda 21—although land use is generally
both water-dependent and water-impacting. In many of those chapters the words
"water", "hydrology" or related words appear less than once in 1000 words.
Further, in the report to the UN Commission on Sustainable Development on the
follow-up activities related to the land use planning chapter 10 of Agenda 21 some
years later, water appears only as a footnote (FAO, 1995).
Neglect of land/water linkages may complicate the identification of regional
characters. A comparison of regional differences in terms of, respectively, water use
to availability ratio and per capita water availability is a good illustration: the
semiarid and subhumid parts of Subsaharan Africa turn out as water-rich
(Falkenmark, 1996). This conclusion is in sharp contrast to all the attention that has
gone into the "droughts and desertification" issue. Earlier work by the author
(Falkenmark, 1993) indicates that the problem of the 20-country "hunger crescent"
in that region is indeed water scarcity rather than a putative water surplus. The way
out of this paradox is to pay attention to both the water in rivers and aquifers (blue
water) and the water in the soil (green water), Fig. 1. Such an approach is now being
taken by FAO (1996) which recently visualized the overall availability of renewable
freshwater in terms of blue and green water and—based on Postel et al. (1996)—the
respective degree of current appropriation.
Rainfall
Productive water loss
GREEN WATER
Unproductive vf|
Run-on
Rivers & aquifers
J BLUE WATER
O Yield impacting
Partitioning points
Fig. 1 Rainfall partitioning into the vertical green water branch, encompassing
productive and non-productive components, and the semi-horizontal blue water
branch, encompassing the water in groundwater aquifers and rivers.
Need for a water cycle-based conceptual framework
In view of the emerging issue of global food security, the new agenda will have to
address the complementary use of blue and green water. It will also have to include
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M. Falkenmark
efforts to avoid pollution from settlements, from industry and from agricultural
chemicals. The new agenda has to be based on a comprehensive understanding of the
ways in which man interacts with the water cycle. The tendency of this cycle to
cascade—through its integrity and continuity—any interferences onwards towards
terrestrial, aquatic and coastal ecosystems has also to be taken into account. In order
to make all this integration possible, conceptual "road maps" have to be provided
that allow effective communication between biologists and geoscientists, between
those with focus on land use and those focusing on water, between water flow
experts and water quality experts, and between natural scientists and political
scientists and decision makers.
In a world pushing against water-related constraints, a water illiteracy among
politicians and decision makers is evidently hazardous. It is the duty of scientists to
convey an understanding of the central role played by water in life support systems.
For example, a broader understanding has to be created of fundamental regional
differences in terms of environmental preconditions for human activities (ECOSOC,
1997). One general challenge of governance can be said to be to cope successfully
with environmental systems in the landscape while seeking to meet relevant societal
needs. What is needed is a framework which allows one, for example, to clarify
better the two economic "mantras" ("water as an economic good", "water has to be
priced"). What water should be paid for: river water, groundwater, the provision of
artefact water, soil water, or rain water itself? The main goal is simplification and
visualization without water reductionism.
This paper addresses the need for a simple explanatory model and a conceptual
framework which allows an overview of humanity's overall predicament. It feeds on
the author's efforts during past decades to visualize fundamental linkages between the
water cycle and human activities.
SUSTÀINABILITY-RELATED CONSTRAINTS TO HUMAN ACTIVITIES
Water's multiple functions
Water has basically four main functions which have to be taken into account in
developing a proper coping policy (Falkenmark & Lundqvist, 1995):
- health function as manifested in the fundamental importance of safe drinking
water as a basic precondition for socio-economic development (cf the massive
efforts that went into the International Drinking Water Supply and Sanitation
Decade 1981-1990);
- habitat function of water bodies, hosting aquatic ecosystems, which are easily
disturbed when the water in the water bodies gets polluted;
carrier function for dissolved and suspended material picked up by the mobile
water along its pathways through atmosphere, landscape and water courses, and
carried along; this function plays a central role in the land degradation processes
(leaching of nutrients; erosion and sedimentation); and
- production function in economic development. There are two production
Society 's interaction with the water cycle
455
functions to distinguish: (a) biomass production, operated by a flow of "green
water", entering through the roots and leaving through the foliage; in the absence
of "green water", photosynthesis stops altogether and the vegetation wilts; and
(b) societal production in households and industry, based on "blue water",
withdrawn while passing through the landscape, and delivered to cities and
industries through water supply systems.
Different water functions are relevant for different sectors of society, each driven
by its own political driving forces. The fact that the integrity of the water cycle links
all these sectors together is a tremendous challenge of interdisciplinary, interprofessional and intersectoral communication (Fig. 2). The goal must be to master
the whole system. In these efforts hydrologists are essential team members.
Cycling water— its multiple functions
Fig. 2 The political driving forces influencing water in its different functions are
sectoral. Society has to find effective ways of coping with the fact that water cycle
integrity integrates the outcome. Each sector has its own water-related problems and
the deep involvement of water in society leads to societal threats if water is being
mismanaged.
Main land/water interactions
Two of the water functions mentioned are particularly linked to land use: the two
production functions based on respectively green and blue water, on the one hand;
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M. Falkenmark
and water as a carrier of solutes and silt, on the other.
The whole issue of global food security is closely linked to water availability. So
are the possible constraints introduced to national food self-sufficiency in a dry
climate, especially where there are limited possibilities to make additional water
available for irrigation (FAO, 1996). However, forestry is also a water-dependent
activity. Even moderate changes in the vegetation cover may, especially in climates
with high evaporative demand, be reflected in non-negligible alterations of water partitioning (Szesztay, 1994). It is well known that forest clearing may produce waterlogging, whereas reforestation and afforestation may take their cost in terms of
reduced runoff, i.e. benefits foregone for downstream water uses. The complementarity between green and blue water may lead to a new generation of problems in
international river basins. The issue is not just how to share the blue water flow in
the river. Rather, it is how to share the precipitation over the river basin. This leads
to a new question, now being raised among water lawyers (McCaffrey, 1997): who
owns the rain?
A particular case of water-dependent land use is urbanization. Rapidly growing
urban areas increasingly compete with rural areas for water that now goes into
irrigated agriculture. One well known example is reflected in the water banking
system in Arizona (Morrison et al., 1996). A less well known example is the dispute
between two neighbouring states in India for water from the Bhavani River. The
challenging question raised is "water for food or fashion?" (Blomqvist, 1996). In
poor regions with simultaneously growing food needs and rapid urbanization, the
conflict is evident.
In dry climate regions large amounts of water may be lost by non-productive
return flow to the atmosphere. As an average for the Southern Africa region some
65% of rainfall gets returned to the atmosphere by evaporation; only 20% feeds the
root zone with green water, while only some 15% is left to recharge aquifers and
rivers with blue water.
The task to minimize water pollution is another complex issue. Minimizing point
discharges is more a question of convincing and financing than of technological
deficiencies. When it comes to indirect pollution from land-based sources such as air
exhausts, acidifying gases, land fills and waste deposits, or agriculture, the issue is
more complicated. One is back to the question of first providing proof. Geoscientists
have failed in their pedagogical task to make people understand that water carries
soluble matter along in the water cycle. Society still acts as if what cannot be seen
does not exist. The result is widespread nitrate and pesticide pollution of groundwater, and eutrophication of rivers, lakes and coastal waters. The action barriers to
overcome are high (Stockholm Water Symposium, 1996).
Unavoidable manipulations
A first "road map" needs to link the societal sphere to the landscape sphere. Human
activities in the landscape are driven by societal demands for life support as
influenced by expectations in society, by population growth increasing the number of
Society 's interaction with the water cycle
457
Human activities in the landscape
^
! .ahdscape
sphere
T
Oocia! sphere
Proactive imperative
Societal requirements
-food
- water
- energy
- hazard prevention
Needs
<>
<F
Satisfaction
of needs
Waste production
4>
Waste output
Natural resources
- water
- biomass
- energy
- minerals
Landscape manipulations
land
• physical
water
waste
Changed
policies
- chemical
Frustration
agricultural
chemicals
Reactive responses
- passive
suffering
morbidity
famine
poverty
disputes
- active
env.migration
mitigation
conflict resolution
Side effects
Changed
behaviour
Intensified
resource
problems
Environmental side effects
Frustration
<F
-
air degradation
land degradation
water degradation
ecosystem degradation
Fig. 3 Fundamental interrelationships between the social sphere and the landscape
sphere.
individuals expecting life support, and by growth aspirations within the economy, in
particular the industrial sectors. Some main linkages are shown in Fig. 3 based on
the idea that life support of the population is the basic proactive imperative expected
from the leaders of a society (Falkenmark & Lundqvist, 1995). They have to secure
or at least facilitate the availability of food, water, energy, but also hazard
prevention. Failure in this regard will have a high price: morbidity, famine, poverty,
disputes, riots and even revolution.
The provision of life support components involves not only interferences with the
landscape, physically by manipulating land as well as water, and chemically by waste
generation, but also the introduction of agricultural chemicals to increase crop yields
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M Fatkenmark
as necessary. The benefit is the satisfaction of the societal needs. However, due to
the natural rules operating in the landscape, there will also be environmental side
effects as consequences of the interferences: air quality degradation, land productivity degradation, water quality degradation, and also, as higher order effects,
ecosystem degradation.
When society reacts to these environmental consequences, the responses may be
passive or active. The passive ones are the same as if the life support does not
function properly but is now exacerbated by the environmental problems superimposed on the supply problems viz. morbidity due to polluted drinking water or
seafood, famine due to land fertility degradation, disputes due to controversies about
land and water use etc. The reactive responses may also be active: on the individual
level by migration or adaptive behaviour such as fallow reduction; on the societal
level by policy responses.
Since manipulations are unavoidable in order to harvest the natural resources,
and these manipulations will, in addition to the benefits, produce side effects,
sustainability criteria are needed to find out how to protect the resource base from a
long term undermining by water pollution, land degradation, and, as higher order
effects, ecosystem and biodiversity degradation. A set of intergenerationally defined
criteria has been proposed earlier by the author (Falkenmark & Suprapto, 1993):
- human-ecological: groundwater to remain drinkable, land to remain productive,
crops and fish to remain edible;
ecological: valued ecosystems to be protected from degradation, biodiversity to
be protected; and
- resource-economic: water resources to be protected from overexploitation.
CARRYING CAPACITY IMPLICATIONS
Water is accessible for societal use while it passes through the landscape, above and
below the ground surface. The water cycle therefore provides life support constraints
both in terms of the green water dependent biomass production potential, and of the
blue water dependent socio-economic production related to health, industry and
urban activities. Polluted water adds further constraints. In order to facilitate a
dialogue with ecologists on these constraints, they might be translated into a carrying
capacity language.
Linking to the ecological carrying capacity concept
The basic biological concept of carrying capacity refers to one particular species and
defines the maximum size of the population (Cohen, 1995). Basically, the sustainable
population density depends on several factors:
- exterior environmental factors (abiotic factors);
- interior biotic factors in the sense of density-dependent extrinsic as well as
intrinsic regulating factors: interaction with other species and the population's
own response to density respectively.
Society 's interaction with the water cycle
459
external feedbacks ~
other
/ " species ~\
modifying
technology
*" , popu
population
Jnner
JJ
feedback/
external feedbacks -
population driven
management driven
technology driven
- management driven
population driven
Fig. 4 Translating water-related life support constraints into a population carrying
capacity concept: (a) the ecological concept distinguishing between inner and
external feedbacks; (b) an extended concept including human-developed modifying
technology (to enhance the resource by reducing basic constraints, and to manage
the resource during its use) and its external feedbacks; and (c) further extended
concept, clarifying the environmental constraints and adding land/water interactions
and their respective feedbacks with the distinction of external feedbacks between
population-driven, technology-driven and management-driven.
A schematic system representation is indicated in Fig. 4(a).
Proceeding to the human species, man is able to increase the carrying capacity of
a region through human-developed technology. He removes basic constraints in the
outer environment such as inundation risk, waterlogging, lack of nutrients, water
shortage etc. The abiotic constraints are manipulated both through development
technology and through technical measures related to resource use. A schematic
representation is indicated in Fig. 4(b). Besides the population-driven feedback of
overexploitation there is now an additional technology-driven feedback with
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M. Falkenmark
eutrophication producing nutrient leakage, water quality deteriorating leakage of
pesticides, etc.
Soil productivity and green water
In applying this approach to the green water-based soil productivity system, the
water-related constraints can be removed by either technology or management
measures. Both of the primary constraints call for measures to secure root zone water
availability, or adapt the plant water demand to the current water availability. The
former case involves small-scale irrigation from locally stored flash floods, or
regional-scale irrigation systems (e.g. Mahaveli in Sri Lanka, command areas in
India). The latter case can be managed by crop selection, by introducing good and
bad weather codes to the farmers, by growing a mix of seeds that includes droughtresistant species etc.
The modifying technology is basically of two types:
- technology aiming at initial enhancement of basic growing conditions by clearing
of natural vegetation, drainage, flood mitigation, etc.; and
- technology aiming at the continuous management of agricultural production such
as tillage, fertilization, crop selection, soil conservation, etc.
Both types of activities produce negative feedbacks, partly purely technology-driven,
partly management-driven. Conventionally both are lumped together as "environmental impacts". The long term sustainability of the system may be disturbed if the
feedback to soil productivity from the soil management involves irreversible damage.
Evidently, conservation of long term productivity of the soil depends on the capability within society to manage quite complex systems of components and
interactions.
Water availability for blue water uses
Water is made easily accessible through technology: pumping from drilled wells,
withdrawal from rivers and lakes, transport through canals and pipelines, distribution
through urban water supply systems, etc. Seasonality of river flow may be changed
through storage and flow control. All these water resources development activities
have feedbacks: changes in sediment transport, in groundwater tables, in water stages
of rivers and lakes, etc. There are also feedbacks related to the necessary movement
of inundated human settlements, to changed human ways of life etc. Once water has
been used, the sullage and waste water is returned to the river or infiltrated into the
ground. Water use-related feedbacks include not only pollution but also salinization
from the return water from irrigated areas.
Limitations in the carrying capacity exist because the freshwater recharge of
aquifers and rivers is limited and therefore constrains the withdrawal potential per
unit of time. This will limit the population which can be supported from the
resource—on what level will depend on the water demand, the population growth,
Society 's interaction with the water cycle
461
and the general expectations regarding per capita water needs. Furthermore, water
pollution will reduce the usability of the available water.
Water and land have to be integrated
The close interactions between water and land make it necessary to integrate the two
carrying capacity approaches (Fig. 4(c)). Presence of root zone water is a basic
condition for land productivity: biomass production returns water to the atmosphere
through the transpiration process as such but also through evaporation of the water
intercepted on the foliage or from moist soil between the plants. Land use is waterdependant but also water-impacting. It necessitates interventions with soil/vegetation
with consequences for the water partitioning at the ground surface and therefore for
the flow regime. Land use involves pollutants spreading in the landscape which are
dissolved by the moving water and transported to aquifers and rivers.
WATER CYCLE-BASED OVERALL SYSTEM
Water cycle and human ecology
Figure 5 visualizes in a schematic way Man's interaction with the water cycle against
the background of its integrity. Human activities in this mental image include two
main types of landscape manipulations (including its water systems):
- chemical manipulations: agricultural chemicals; waste output to atmosphere,
land, and water systems; and
ATMOSPHERE
waste
gases
recipitation
MAN
manipulation of b
•sow—^"
fe
t,
evaporation
sea evaporation.
LANDSCAPE
vegetation
groundwater flow
water
supply
flood
flow
fh
_ d _ J WATER BODIES
waste
water flow
OCEAN
river
flow
a, b, c and d: human interventions
e, f, g, and h: water flows
Fig. 5 Mental continuity-based image of the water cycle, linking the net sea
evaporation, the wetting of continental landscapes, the recharge of aquifers, the
floodflows in rivers, and river discharges back to the sea. Man's interactions are
indicated by the four horizontal arrows to the left: waste gas output to the
atmosphere; manipulation of soil/vegetation—physically and chemically; water
withdrawals from aquifers and rivers; and waste water output to water bodies.
When population grows, these arrows will grow in size, whereas the water flow
arrows in the system will change only when the climate changes.
462
M. Falkenmark
-
physical manipulations: (a) land manipulations to harvest biomass, for settlements, etc.; and (b) water system manipulations: withdrawals from aquifers and
rivers, water transfers to urban areas, reservoirs to overcome seasonality and
protect from floods and inundations.
In Fig. 6(a), a second step is taken. It distinguishes two human systems: an
urban/technical system where socio-economic production takes place, supplied with
water withdrawn from groundwater aquifers and rivers; and a rural system, where
rainfed food and biomass production take place. Grey squares have been introduced
in the Figure to symbolize respectively rural and urban land use. Water is withdrawn
from aquifers and water bodies and conveyed through the urban system. One branch
supplies the rural system with irrigation water, the other conveys waste water back to
a water body. Water is finally made accessible, when and where needed, by technical
systems for withdrawals and water resources development structures.
Benefits are produced by Man's different ways of interaction with the water
cycle in order to secure food, fibre, fuel wood, timber, water, energy etc. The
interactions however also produce side effects. Figure 6(b) shows the side effect
perspective in terms of changes in water flows, pathways and quality generated by
the interactions. Pollutants emerge from rural land use (e.g. agrochemicals) and from
urban water use (household and industrial pollutants). The result is quality effects on
ground water and river water. Water resources structures involve landscape changes,
which generally have side effects, for instance on flora and fauna upstream and
downstream. Emission of polluted water—more or less treated-^into water bodies
produces quality disturbances there, with higher order effects on aquatic biota.
All these effects of different types of human interventions with water flows,
pathways and quality are superimposed on each other, producing combined
ecological effects in water bodies and coastal waters. As Man consumes water from
polluted sources and eats fish from degraded water bodies, health effects are
generated.
The fourth step focuses on the control points in the system, i.e. the ways in
which Man tries to take control over land and water use and their water cycle-related
consequences, and by which the system is presently operated. Figure 6(c) shows
what can be spoken of as control tools. Blue water use is regulated through
withdrawal permits, pricing of provided water, waste water treatment, and emission
regulations. Green water use is seen as a basically implicit part of rural land use and
is seldom regulated in any similar way.
Sustainability implications
Basically the overall task of integrated land/water management is—as already
indicated—to cope with the environmental preconditions while satisfying societal
demands (Fig. 3). The present situation in terms of already widespread groundwater
pollution (Gulani, 1996) and land fertility degradation (Brown & Kane, 1995)
suggests that it is already too late in human history to apply the strict intergenerationally-based criteria. What criteria could then be defined for what may be
Society's interaction with the water cycle
463
hydroclimatic
preconditions
water
use
resources
structures
/and
h
quantity
/quality
effects
hydroclimatic
preconditions
stem
cohbined
he. tlth
Rura, k nd
efl sets
use
eff< cts of
rojects
Urt an
land use
water
combined ecol.
effects on coast a/
\
waters
combined ecol. effects
on freshwater
hydroclimatic
preconditions
urban
system
control
tools
Rura
hnd use
land
ise regul,
le jal regul.
fc r water projects
permits 1 ,
- pricing 2
- treatment 3
Fig. 6 Man's interaction with the water cycle within urban and rural water use:
(a) water use alternatives; (b) side effects of the interactions in terms of quantity/
quality effects as well as higher order effects on ecosystems and human health; and
(c) the different control tools.
seen as a successful coping in line with the task under discussion? This will of course
involve value discussions. In other words a sort of "semi-sustainability" criterion,
where the best possible approach is taken in balancing human needs and human
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M. Falkenmark
rights (safe water, food, poverty eradication) against the side effects resulting from
the necessary manipulations with landscape components. This will involve efforts to
protect valued environmental legacies, to minimize water losses wherever water is
scarce (whether blue or green), to avoid overexploitation of the finite water
availability, and to minimize pollution from various waste and chemicals introduced.
In order that man/land/water interactions be sustainable in the sense of not
continuing to undermine the land and water productivity for future generations, the
future strategy has to involve certain criteria:
- Demands for blue water have to be adapted to the amounts that can be made
accessible. The implications in terms of policy will have to address both urban
water use and agricultural irrigation in terms of adaptation as well as pollution
avoidance. Tools to be used may include pricing tariffs, permits, etc.
- The amounts of water needed for urban use and irrigation have to be made
accessible. This will involve water resources development structures like water
reservoirs, channels and pipelines for transfer to urban and agricultural areas etc.
Side effects of these structures have to be minimized, and unavoidable side
effects seen as acceptable.
- In rural land use, non-productive water losses have to be minimized. This is
equivalent to maximization of green water productivity within rainfed agriculture, i.e. maximize the production per unit of water added to the area by precipitation. The implications in terms of policy involve tools to facilitate but also to
complement, by food import, limitations in terms of food production potential.
For that purpose, societal development has to be directed towards the earning of
foreign currency needed.
- Waste handling has to be managed in such a way that pollution is minimized.
Planning will constitute a key mechanism to integrate all the components. The
catchment or river basin should be the basic areal unit for such integrated
man/land/water planning. An integrated approach to land and water use and productivity has to be taken. Other main components include adequate policies to make
comprehensive management possible; water resources development structures to
make the needed water accessible when and where needed; and careful control of all
relevant sources of pollutants. Adequate human capabilities, legislation and administration have to support these efforts. Economic and other incentives are needed to
secure the implementation of the new agenda.
CONCLUSIONS
The present global predicament emerges from the global water cycle on which two
main threats are posed: the increasing food needs involving major consumptive use
of water which will be returned to the atmosphere, not available for immediate reuse;
and the increasing pollution threats from conventional economic development
reducing the usability of the readily available water.
The non-undermining criteria for human use and interactions with the circulating
water lead to carrying capacity implications. The biologically defined carrying
Society 's interaction with the water cycle
465
capacity concept has in this paper been developed to merge both soil productivity and
water productivity into an integrated carrying capacity concept. Such a conceptual
framework might be useful in considering what conclusions have to be drawn from
potential future internationally prescribed sustainability directions.
The overall system has been described from a water cycle-based perspective with
the aim to facilitate the dialogue needed between all the different participants
involved in preparing for livelihood security and quality of life for a rapidly
expanding world population. This particular perspective would secure that the
non-negotiable character of the water cycle integrity is entered as a basic component.
The central role of water in biomass production is emphasized as a countermeasure
against today's widespread land/water dichotomy. Such a description would allow a
comprehensive overview of human interactions with the circulating water, and can be
used as a base for intersectoral communication and for analyses called for to avert
the looming water crisis since human demands and aspirations are rapidly growing.
The joint goal will be to seek attainable compromises between manipulations needed
and necessary limitations of the side effects produced. Such compromises have to be
based both on value considerations and on the need to protect the productivity of the
resource base for the support of the next generations.
This paper has tried to visualize both the links between green and blue water,
and the links between human activities and the water cycle. The central role played
by the water cycle and a widespread water illiteracy make it essential that
hydrologists take part in efforts to address the life support needs of humanity.
Climate change will escalate such needs.
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