UN Population Division, Department of Economic and Social Affairs,
with support from the UN Population Fund (UNFPA)
|
| UN Population Division, Department of Economic and Social Affairs, with support from the UN Population Fund (UNFPA) |
|
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This document is being made available by the Population Information
Network (POPIN) Gopher of the United Nations Population Division,
Department for Economic and Social Information and Policy Analysis,
in collaboration with the Population Programme Service, Sustainable
Development Department, United Nations Food and Agriculture
Organization. For further information, please contact: Mr. Jacques
du Guerny, email: jacques.duguerny@fao.org
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Population and the environment:
a review of issues and concepts
for population programmes staff
I.
POPULATION AND WATER RESOURCES
September 1994
FOREWORD
This paper is the first in a planned series of four to six
notes, designed to bring to the attention of Country Support Team
Advisers (and staff of UNFPA programmes concerned) state-of-the-
art information on major population-environment issues and
methodological advice for dealing with such issues in the context
of population policy work and population/development programmes.
The purpose of each paper will be to help fellow population
specialists at the regional and country level carry out (directly
or through project formulation, backstopping and operation)
certain tasks such as:
- promote awareness of population and environment linkages
and related issues, qua relevant elements in development
policies;
- help integrate environmental concerns and considerations
in population policy analyses;
- help design or carry out population-centered research in
support of development policy studies; or
- help design data collection and monitoring systems on
population/environment issues.
For this purpose, each paper will provide factual
information on the environmental issue(s) under review, try to
elucidate the role of population variables, propose analytical
tools and examine statistical information problems where
appropriate.
This first paper focusses on water resources issues, which
we believe to be of crucial and growing importance--indeed,
likely to surpass as yet better-publicized issues such as
deforestation, atmospheric pollution or soil degradation in many
countries. An indication of this importance is FAO's decision to
celebrate this year's World Food Day (16 October 1994) on the
theme: "Water for life".
Although self-contained, this paper is supplied with a
"companion document", namely a special chapter of FAO's State of
food and agriculture 1993 on "Water policies and agriculture",
to which many references are made in the text.
This paper will be first addressed to Country Support Team
Directors, Advisers on Population and Development, and FAO
Advisers. Suggestions for further distribution and requests from
field projects will be welcome.
Alain Marcoux
FAO/UNFPA TSS
==================================================================
CONTENTS
1. INTRODUCTION 4
2. POPULATION DYNAMICS AND DEMAND FOR WATER 5
2.1 Domestic and municipal usages 5
2.2 Agricultural usages 6
2.3 Industrial usages 8
2.4 Overall use and competition between sectors 9
3. IMPACT OF POPULATION ON WATER SUPPLY 9
3.1 Impact on surface water 9
3.2 Impact on groundwater 10
3.3 Water pollution 11
4. IMPACT OF CHANGES IN WATER SUPPLY ON POPULATION 13
4.1 Water scarcity 13
4.2 Water pollution 16
5. POPULATION-WATER LINKAGES IN A POLICY FRAMEWORK 18
5.1 Policy relevance of the linkages 18
5.2 On analyzing population-water linkages 19
5.2.1 Factors in water withdrawal 20
5.2.2 Factors in water pollution 22
5.3 Policy options 23
5.4 Knowledge base and research needs 25
5.4.1 Research topics 25
5.4.2 Indicators 27
NOTES 29
ANNEXES
==================================================================
"Despite enormous expenditure [...] supplying
water for food production, drinking water,
fisheries and environmental protection has not
kept pace with population and economic growth.
The loss and degradation of rivers, lakes,
wetlands and other water-dependent ecosystems
around the world has been the result, along with
declining human health."
1. INTRODUCTION
Of all natural resources, water is the most essential. It
is fundamental to all vital processes of value to mankind. It
seems abundant at first sight--almost 70 percent of the earth's
surface is covered with water. Yet perhaps 2 billion people live
in areas with chronic water shortages. Quantitative supply and
water quality problems are mounting and could constrain economic
development and human well-being in general. In other words,
water no longer can be taken for granted: "Ensuring that present
and future generations will have adequate food and water, and
concurrent maintenance of the resource base and the environment,
are two of the most challenging tasks that have ever faced
mankind".
Populations require water for domestic and municipal usages;
as an input in productive activities: agriculture, industry
(including energy production) and services activities; and
finally, in all usages, for the evacuation of effluents
(sanitation, removing industrial wastes etc.). Demands from all
these sectors are mounting and competing with one another.
To understand the nature of resource use issues in this
area it is necessary to keep in mind some characteristics of
water supply. First of all, the seemingly abundant availability
of water is misleading. Freshwater--the only usable kind, as far
as human needs are concerned--is only a small fraction (2.5
percent) of the water present on our planet. Further, most of
freshwater is in the form of permanent ice and snow, or of
groundwater which, given its life cycle of several thousand
years, must be regarded as unrenewable on a human time scale. In
the end only 0.3 percent of freshwater is renewable.
Runoff, however, easily compares with human needs at the
global level. But "usable flow is substantially less than
runoff. Water supply scarcity may become a major constraint on
socio-economic development at levels of use substantially below
total runoff". In addition, as with most issues, the global
level has little relevance. Water supply is irregularly spread
over space and often is not found where it is needed. It is also
irregularly spread over time, while time constraints on water use
are strong, especially for domestic uses and industry which
require a basically constant supply.
These natural conditions set absolute limits to human use:
"Human innovative talents can make the best possible use of the
water that passes through [...] a country, but technology cannot
influence the rate at which water is naturally renewed from the
global water circulation system". Water therefore is a finite
resource: "The water cycle makes available only so much each year
in a given location. That means supplies per person drop as
population grows".
Unlike other resources, water is mobile and necessitates
catchment, transportation and storage, with related costs and
efficiency problems. Ultimately water availability can be
regarded as a function of the costs of delivering water at the
required place and time, rather than as a physical parameter. But
those costs can be high and consumers usually are reluctant to
bear them because of age-old perceptions of water as a free good.
Finally, water resources are vulnerable, meaning that their
flow patterns and chemical properties can easily be altered by
human activities and natural factors in ways which negatively
affect subsequent human usages. Quality considerations are
important whatever the utilization of water: industrial,
agricultural and domestic usages all have their criteria of
adequacy (particularly strict ones in the latter case).
2. POPULATION DYNAMICS AND DEMAND FOR WATER
2.1 Domestic and municipal usages
These are the "basic" usages of drinking, food preparation,
domestic hygiene and the collective usages at the community level
(heating, fountains, pools etc.). Per caput levels of domestic
use increase as general levels of well-being and aspirations
rise; in addition demographic factors contribute heavily to shape
water requirements in this sector.
Population growth is a direct determinant of increases in
water demand for domestic uses. Another key demographic factor
is change in the geographic distribution of population, which
modifies the spatial pattern of demand for domestic uses.
Urbanization, in particular, through increased population density
and the concentration of demand, can make the latter a serious
constraint on local resources. Many third world cities are
critical areas from the viewpoint of water supply (see Annex 1).
Problems are especially acute when urban growth is based on the
migration of rural poor rather than on economic growth.
The magnitude of the requirements brought about by
population growth and urbanization is revealed by the extent of
unmet needs. Despite an international effort to promote the
development and implementation of water and sanitation plans
under the 1981-1990 International Drinking Water Supply and
Sanitation Decade, progress at the end of that period still was
inadequate. The number of people lacking access to clean drinking
water had been reduced by one third, but still stood at more than
1.2 billion, or 23 percent of the world population. Relatively
greater progress had been registered in rural areas, where the
number of people in need had been reduced from 1.6 to 1 billion.
But the rural population still lagged behind the urban (37
percent unserved against 18 percent). As to the number of people
lacking access to adequate sanitation services, it was unchanged
at 1.7 billion after ten years. More than half of the rural
people were affected against 28 percent of the urban.
Globally, making substantial progress on the urban and rural
water supply front would require a tripling of investment over
1980s levels. The bulk of investment in water supply and
sanitation so far has been directed to the urban sector and the
better-off population, with persisting inequalities as a
result. In principle urban concentrations should enable
economies of scale, but growing numbers can be overwhelming.
Human beings need only about 5 liters of water each day for
cooking and drinking; according to WHO, however, good health and
cleanliness require a total daily supply of about 30 liters per
person (11 cubic meters per year). By comparison, regional
levels of per caput withdrawal for domestic and municipal usages
are estimated as follows:
World ................... 52 m3/year
Africa .................. 17
Asia .................... 31
North/central America ... 167
South America ........... 86
Europe .................. 92
Former USSR ............. 90
These figures refer to usage regardless of the quality of
water used; the latter can be a major problem, as seen above.
This being said, basic needs are sometimes abundantly covered,
indicating a variable amount of wastage, particularly in
developed regions. It is a fact that access to stable and easy
supply--in particular water on the tap in urban settlements--
stimulates use considerably.
Globally, water withdrawals for domestic and municipal
usages account for a modest part of the total: 8 percent (see
Annex 2). But they are growing rapidly. By 2000, withdrawals are
expected to double with respect to their 1980 level and to reach
11 percent of total use (see Annex 3). Population growth,
especially that which will occur in third world cities, would be
responsible for a substantial part of this increase.
2.2 Agricultural usages
Irrigation has been and remains of vital importance for the
provision of food and employment for growing populations world-
wide. In developing countries irrigated areas represent 16
percent of all cropland and provide 37 percent of the production-
-implying a productivity three times as high as that of other
lands. Irrigation and improved seed varieties were the basis
of the "green revolution" which made most of Asia self-sufficient
in food. But water requirements for irrigation are extremely high
in comparison to the output: "Crops require and transpire massive
amounts of water"; this makes water "the major limiting factor
for world agricultural production". Depending on the crop and
the location, producing one ton of cereal requires between 500
and 2000 tons of water (wet paddy being the most wasteful).
Since one ton of cereal covers the annual consumption of about
four persons on a world average, it can be estimated that the
average consumer of irrigated cereals thus indirectly uses about
400 tons of water per year--to be compared with the few tons per
caput required for domestic use.
Indeed, agriculture is the major water user world-wide:
around 70 percent of total withdrawals are for irrigation (Annex
2). Regional levels of water use by agriculture on a per caput
basis are the following (compare with the levels of domestic use
above, calculated from the same source):
World ................... 444 m3/year
Africa .................. 216
Asia .................... 446
North/Central America ... 912
South America ........... 282
Europe .................. 235
Former USSR ............. 832
As demand for agricultural products increases, needs for
additional irrigated land and corresponding water supplies also
mount. Globally, irrigated areas have increased from about 50
million hectares in 1900 to 100 million in 1950 and more than 240
million now, mostly to respond to growing third world needs.
Recent projections of agricultural demand to 2010 are shown
in Annex 4. The role of population growth in the projected
increases in demand can be estimated from these figures, as
follows:
Respective shares
of the growth in:
per cap.
population demand
World 89% 11%
Developed countries 100% 0%
Developing countries 68% 32%
Africa 97% 3%
Near East 86% 14%
East Asia 43% 57%
South Asia 71% 29%
Latin America 75% 25%
FAO estimates for 130 developing countries between 1990 and
2000 indicate that providing for those requirements will require
15.2 million hectares of new irrigation development, over and
above the existing 172 million hectares. In addition, more than
17 million hectares of existing irrigation schemes will need to
be upgraded; small-scale water programmes and conservation
actions will be needed on 10 million hectares in rainfed
areas.
To enable this expansion of irrigation, water withdrawals
are projected to increase by about 17 percent globally. According
to the projections of Annex 3, water use by agriculture is
expected to grow rather slowly if compared to other usages (about
one percent annually) but the additional requirements will be
very large in absolute terms: twice the additional domestic
requirements, and roughly equal to those of industry in the low
projection for the latter sector. This will create severe
competition between sectors in regions with limited water
resources and a potentially growing industry.
Irrigated areas will not expand again at rates comparable
to that of world population growth as they did in the 1960s and
1970s. This is partly due to the ever scarcer availability of
hydrologically favourable sites. These natural conditions
increase the costs of irrigation development. The need to adopt
preventive measures against irrigation-induced land degradation
compounds this factor. This, in combination with the frequent
social, health and environmental costs, has actually discouraged
lending, at least for large-scale irrigation.
In the medium term, population and economic growth will
exert even greater pressure on water resources than on land.
Africa and Asia already suffer from diminishing per caput water
supplies, and many countries already are closer to their water
resource limits than to their land limits.
2.3 Industrial usages
Like other human activities, industrial production is
dependent on water for processing, cooling and evacuation of
effluents. This category of needs is rapidly increasing.
Population growth contributes to that increase, although in a
minor way: income growth and the diversification of needs play
a bigger role in this case.
Per caput water withdrawals for industrial usages are
estimated as follows:
World ................... 148 m3/year
Africa .................. 12
Asia .................... 42
North/Central America ... 782
South America ........... 110
Europe .................. 385
Former USSR ............. 346
According to the forecasts of Annex 3, global requirements
will increase by at least 50 percent, and perhaps 70 percent,
between the 1980s and 2000. The fastest growth is expected to
take place in Africa and South America, but the largest absolute
increases by far will be in Asia.
2.4 Overall use and competition between sectors
Total per caput withdrawal levels vary enormously, from less
than 10 to more than 6,000 cubic meters per year. The lowest
levels are found in poor developing countries, mainly in Africa.
The highest levels are found in a few countries with high ratios
of irrigated land per caput (Iraq, Pakistan and central Asian
Republics of the former USSR).
In the second half of this century water withdrawals
increased between and 4 and 8 percent annually. Water use is
still growing in the developing countries, but stabilizing in the
industrial countries. As a result, global withdrawals are
expected to rise at only 2 or 3 percent annually during the
1990s. Yet supply problems will keep mounting: freshwater is
being extracted from some river basins at rates approaching those
at which the supply is renewed and from some underground aquifers
at rates exceeding natural replacement.
Water demand patterns of the future will be characterized
by growing competition between sectors, especially in developing
countries. That competition will be particularly intense around
the cities, where the demands of households, industrial plants
and agriculture will inevitably put increasing stress on water
(just as on land). If rural users are deprived of water resources
in the process, this will accelerate migration to the cities.
In the developed world, use levels are stabilizing; water-
saving modalities of use and water re-use are gradually expanding
as the costs of water supply and treatment are better charged to
users. In developing countries the margins for increased demand
are considerable, on account of rising industrial sectors, unmet
domestic and municipal needs, and agriculture.
3. IMPACT OF POPULATION ON WATER SUPPLY
Human populations affect water in direct and indirect ways.
The former consist in modifications to the circulation of water
and its quality by withdrawals, waste water disposal, river
regulation etc. The latter consist in modifications of vegetation
and soil cover: deforestation and compaction reduce the
absorptive capacity of the soil and accelerate water runoff; this
causes floods and deficits of recharge of aquifers; the loss of
soil protection accelerates erosion and leaching, increasing
water pollution; finally, air pollution affects the chemical
properties of water through precipitations (viz. acid rains).
3.1 Impact on surface water
Human activities affect levels of river runoff principally
by the direct withdrawal of water, the regulation of rivers, and
land uses that change the surrounding environment and affect
watershed dynamics. Disturbances of water flows in turn affect
the wetting of the soil, the recharge of aquifers and rivers, the
quality of freshwater and the per caput availability of water.
Deforestation is a major factor of changes in watershed
dynamics. Forest areas tend to have more stable patterns of river
runoff, because the catchment capabilities of the forest
ecosystem enable a higher amount of groundwater discharge.
Deforestation therefore causes significant changes in river flow
patterns, with accelerated runoff and lost storage, in turn
causing a higher occurrence of flooding in wet seasons and a
greater likelihood of dried-up rivers in dry seasons. Population
growth is an important factor (often overshadowing logging
operations) in deforestation, through the needs for more cropland
and wood.
Examples of this are numerous. The following is a typical
description: "increased runoff due to deforestation has stripped
soil off slopes and deposited it downstream, where it accumulates
in the beds of streams and behind the new concrete dams",
resulting in reduced storage in reservoirs and unstable water
supply; "silt-ridden streams begin to dry up during the dry
season and flood during the rainy season". Ethiopia, "which
has only 6 percent of its forest cover left, is bleeding its
topsoil into rivers at the rate of 2000 tonnes per square
kilometer per year". Such is the disturbance brought about by
loss of forest cover that it can cause water scarcity even in
places with very abundant rainfall. Damage becomes reciprocal
when forests are affected by water disturbances: in the upper
Indus basin in Pakistan, new irrigation canals have disrupted
drainage; increased withdrawals have starved the riverain
forests, in turn enhancing the chances of damaging floods.
Other actions leading to land degradation (such as
overexploitation or overgrazing) have analogous effects on water
regimes. The diagram in Annex 5 illustrates, inter alia, such
processes.
Urbanization--a major demographic trend all over the world--
also has distinct effects of surface water. When streets and
other impermeable surfaces replace permeable soils and
vegetation, the volume, velocity and temperature of local runoff
are increased, reducing the base flow of rivers during dry
periods.
3.2 Impact on groundwater
Because of the climatic and human-induced instability of
surface water, groundwater is important for water supply
security. It also is a primary resource when surface water is
scarce. During the recent decades it has supplied much of the
water needed for burgeoning cities as well as for irrigation
development.
But groundwater aquifers are replenished only slowly, and
human demands often exceed the natural recharge (see Annex 6).
In Tamil Nadu, heavy pumping for irrigation has caused drops in
water table levels of 25-30 meters in a decade. Pumping in
Beijing exceeds the annual sustainable supply by 25 percent; in
northern China, with heavy agricultural, domestic and industrial
demand, water tables are dropping by 1 to 4 meters per year. In
the Bangladesh lowlands, the mining of groundwater for irrigation
has brought about seasonal declines of the water tables; in the
dry season, most village handpumps (the essential source of
domestic water) go dry.
Overpumping of underground aquifers can cause soil
subsidence. Third world urban areas such as Bangkok, Beijing or
Mexico City are affected: buildings, streets, railroads and
sewage systems can be damaged. The phenomenon also occurs in
rural areas (as in various areas across the southern USA).
Overpumping also causes a particular type of pollution in coastal
urban areas where the depletion of the aquifers fosters the
intrusion of saltwater: the problem has been noted in Dakar,
Jakarta, Lima, Manila and parts of Israel, Syria, the Arabian
Gulf, Great Britain and western USA.
3.3 Water pollution
Most human activities contribute to pollute surface and
ground water, either directly (by returning dissolved effluents
to water bodies) or indirectly (because waste deposited on solid
ground finds its way to water bodies). Freshwater is increasingly
polluted by organic nutrients, toxic metals, and agricultural and
industrial chemicals, carried by industrial effluents, land use
runoff, and domestic wastewater. Secondary but growing sources
are the leaching from mine tailings and solid waste dumps, and
atmospheric deposition of pollutants into water bodies.
To the traditional concerns of pollution from organic wastes
and the salinization of irrigated areas, have gradually been
added those of suspended solids, heavy metals, nitrates,
radioactive wastes, organic micropollutants and the acidification
of lakes and streams. Too often, industrial liquid wastes are
dumped in contravention of regulations, toxic and hazardous
industrial and commercial wastes are disposed of in water bodies
or land sites, and systems to dispose of waste water and control
flooding are inadequate.
It is estimated (see Annex 3) that 42 percent of the water
in domestic and municipal usages is returned to the water cycle,
accounting for 11 percent of total waste water. Rapid urban
expansion of the recent decades "has increased the pressures on
the urban environment and on surrounding regions and their
natural resources. It has created immense and growing problems
of air and water pollution [...] In some countries, as little as
2 percent of sewage is treated. From 30 to 50 percent of urban
solid waste is left uncollected. The implications of all the
above for the globe's shrinking supply of freshwater, the health
of urban residents and the integrity of the globe's atmosphere
are obvious".
Much of the pollution arises from the rapid growth of
squatter settlements on the periphery of cities--many of them
springing up on low-lying land and along waterways, and their
wastes flowing into urban water sources. The poor are the most
affected by the deterioration of the physical and natural
environment, both the victims and unwilling agents of
environmental damage.
Most of the water used by industry (87 percent according to
the estimates of Annex 3) is eventually returned to the water
cycle, making up 47 percent of total waste water. It is often
polluted by chemicals and heavy metals; often, also, its
temperature is increased to the detriment of life support systems
downstream. In most developing countries pollution controls,
when they exist, cannot keep pace with urbanization and
industrialization. "Risks from hazardous waste, even if local,
are acute. In some large cities, the daily outpouring of
industrial wastes into water bodies reaches millions of cubic
metres". Things are better in developed countries, but even
there problems exist, particularly in non-OECD countries where
controls on industrial effluents are inadequate.
While industries and domestic sewage are the main sources
of pollution in developed countries, agriculture plays a bigger
role in developing countries due to the clearing of land, the use
of fertilizers and pesticides, and irrigation. The demand for
range- and farmland is a major factor in deforestation. The
resulting accelerated runoff in turn accelerates erosion: in
fact, water erosion globally is the main source of soil
degradation (accounting for 62 percent of severely or moderately
degraded areas world-wide and 70 percent in Asia), and
deforestation is the main cause of water erosion in 43 percent
of the areas affected. Soil erosion in deforested watersheds
increases water turbidity and accelerates the leaching of soil
nutrients. These effects are particularly severe in tropical
regions, especially during the rainy season; but other regions
are not immune.
Irrigation returns only a quarter of its withdrawals to the
water cycle but this return flow accounts for 42 percent of total
waste water. The combined increases in irrigated areas and
related use of fertilizers and pesticides in developing countries
have heavily polluted irrigation return flows, with significant
threats to the aquatic environment as chemicals run off into
streams or percolate into groundwater. Damming itself affects the
quality of water downstream by reducing its nutrient contents and
increasing salinity. Another typical change in land use is the
destruction of wetlands, which removes natural filter mechanisms
and thus allows more pollutants to reach water supplies.
The livestock industry, a major water user in certain
countries (e.g. Bhutan, Brazil, Lesotho, Mauritania, Namibia,
Paraguay) also produces large amounts of water polluted by
organic wastes.
Overall, the greater part of water pollution "is due to
growing populations: the direct effect of the search for protein
and livelihoods, and the indirect side effects of agriculture and
urbanization". Population growth (especially when compounded
by urban concentration) is the source of increasing amounts of
sewage that overload streams and effluent evacuation systems;
third world cities cumulate the problems of industrial and
domestic pollution (see Annex 7). The increase in the use of
chemicals in agriculture, as well as land clearing and
irrigation, are driven by the need to increase production under
the pressure of population growth.
4. IMPACT OF CHANGES IN WATER SUPPLY ON POPULATION
4.1 Water scarcity
Given the essential role of water in human activities, the
impacts of water scarcity are potentially devastating. Those at
the household level may be the most preoccupying as they regard
the most essential aspects of well-being: shortages of drinking
water affect nutrition and health through limited hydratation and
cooking as well as constraints on hygiene. They also affect
workloads, as they entail longer or more frequent trips for
fetching water. Women and children typically are the most
affected on both counts. At the same time water pollution is
worsened, aggravating effects on human health: "Water shortages
usually lead to problems of water quality since sewage,
industrial effluents and agricultural and urban run-off overload
the capacity of water-bodies to break down biodegradable wastes
and dilute non-biodegradable ones". Unfortunately such
shortages are increasingly common.
Water scarcity also limits economic performance, first of
all in respect of agriculture and food production. Agriculture,
being a major water user, is a major victim of water scarcity
when prospects for further development of the production depend
on irrigation techniques.
Overall economic impacts vary, depending in particular on
which sectors are most affected when competition for water
becomes too intense. In certain situations urban and industrial
demand, being backed by greater purchasing power, has deprived
agricultural users. In others, on the contrary, agricultural
withdrawals have left human settlements and industries downstream
short of water. The impacts can be multiple, as in the famous
case of the Aral Sea: reduced river flows induced by large-scale
irrigation development in the region have severely damaged all
the economic activities of what once was the shores of that great
water body, including the destruction of fisheries and declining
agricultural yields.
A method of description for the levels of competition for
water has been developed from the observation of areas where both
per caput supplies and resource use problems were sufficiently
documented. According to this widely used model:
- Population pressures under 600 persons per flow unit
(P/FU; 1 FU = 1 million cubic meters) are not considered a
serious issue, although water quality problems and dry
season supply problems may occur.
- Between 600 and 1000 P/FU, chances of more recurrent
quantitative or/and qualitative supply problems increase
notably; this is called the "water stress" stage.
- Between 1000 and 2000 P/FU such problems are common and
affect human and economic development; this is the
"scarcity" stage.
- 2000 P/FU is seen as the maximum population pressure that
can be handled in the present state of technology and
management capabilities; it has been labelled as the "water
barrier".
These concepts have been used to forecast levels of water
scarcity in 2025 for all countries based on recent population
projections and water supply estimates:
- 15 countries would suffer from water stress, namely
Afghanistan, Burkina Faso, Ghana, India, Korea Republic,
Lebanon, Lesotho, Madagascar, Mozambique, Peru, Poland,
Tanzania, Togo, Uganda and Zimbabwe.
- 9 would suffer from water scarcity, namely Comoros,
Cyprus, Egypt, Ethiopia, Haiti, Iran, Morocco, South Africa
and Syria.
- 22 countries would meet a "water barrier" before 2025,
namely Algeria, Bahrain, Barbados, Burundi, Cape Verde,
Djibouti, Israel, Jordan, Kenya, Kuwait, Libya, Malawi,
Malta, Oman, Qatar, Rwanda, Saudi Arabia, Singapore,
Somalia, Tunisia, the United Arab Emirates and Yemen.
Let us give another example of use of these indicators; it
refers to Africa, whose case is worth noting in this context. The
water potential of the region is not particularly great: when
total river runoff is related to total land area, Africa's index
is only half the global value. The semi-arid areas of the
continent, with their high populations in relation to water
availability, are the most exposed.
Regional prospects point to rapidly increasing water needs:
"improved agricultural yields depend on reducing the risk of
root-zone water deficiency; improved health depends on increasing
household water supplies; industrial development requires ample
amounts of water. In addition to this rising demand, continued
population growth implies that the actual ceiling of affordable
water use would decrease to half its present level in about 25
years". Annex 8 illustrates the interplay of factors
responsible for this precarious situation, including rapid
population growth which is typical of this region.
Table 1 classifies African countries by: [a] level of water
competition, i.e. the number of persons per flow unit and [b] the
technological level of cultivation needed to ensure food self-
sufficiency in 2025, based on FAO's classical study of potential
population-supporting capacities.
Table 1. Countries of Africa classified by level of water
competition and level of agricultural intensification needed
in 2025 for self-sufficiency.
______________________________________________________________
Technology for self-sufficiency:
Low Intermed. High level High level
level level enough not enough
_______________________________________________
Competition
(P/FU):
< 100 Cameroon Sierra Leone
Centr.Af.R.
Congo
Equ.Guinea
Gabon
Guinea
Gui.Bissau
Liberia
100-600 Angola Botswana Mauritania
Chad Ghana Namibia
Cote-d'Iv. Mali Niger
Zaire Sudan Senegal
Zambia
Water stress Benin Ethiopia
(600-1000) Burkina F. Uganda
Gambia
Mozambique
Water scarcity Tanzania Nigeria Algeria
(1000-2000) Togo Egypt
Zimbabwe Lesotho
Libya
Morocco
Somalia
Water barrier Malawi Burundi
(> 2000) Kenya
Rwanda
Tunisia
______________________________________________________________
Twenty-one countries are expected to be beyond the 600 P/FU
threshold by 2025. Eleven of them (bold characters) would be in
that situation already by the year 2000. In 2025 the population
affected by water supply problems would thus reach 1.1 billion,
or about two-thirds of the projected population of the region.
Population growth "is at the heart of the problem of semi-
arid development. [...] The fundamental importance of water both
for habitability and for rural access to biomass for food,
fodder, fuelwood and timber makes water scarcity a crucial
problem in the struggle for a higher quality of life of poor
rural populations [...] Migration out of the area will inevitably
occur if habitability is reduced by water shortages".
Admittedly, scarcity-related concepts are indicative, in
view of the varying adaptive capacities of countries. In
particular, the water barrier concept should not be taken
literally; even if water shortage is indeed a medium-term barrier
to development--especially in developing countries--there is no
indication that solutions for the long term cannot be found.
Rather than impending absolute physical limits, the indicator
warns of steeply increasing costs of supply on account of
increased investment and recurrent expenditure for water supply,
treatment and/or re-use (see 5.3).
It is fair to add that margins for interpretation of
scarcity indices at the country level go both ways: "in the humid
zones, a competition level of 600 might signal the beginning of
water allocation problems. In arid conditions, the problem is
more complex because of considerable seasonal variations in
rainfall. The largest need for irrigation water is during the dry
season when the water accessible to people can be as low as 10
percent of the annual flow. Even countries with an average
competition level of only 50 [...] have considerable allocation
problems during the dry season". In addition, "national figures
do not reflect the stress on water resources quality in local
areas exerted by rapid urbanization and industrialization".
4.2 Water pollution
Water pollution can render the water unfit for various
usages, from nutrition to agriculture and industry. It also can
affect natural biological systems, as in the eutrophication of
lakes and coastal waters or the accumulation of unsafe levels of
metals and organic residues in aquatic life. The quantitative
supply of water certainly can be a local issue, but in many
regions the most serious problem hindering the utilization of
water resources is the deterioration of water caused by
pollution.
Health impacts probably are the most preoccupying: the "use
of polluted waters for drinking and bathing is one of the
principal pathways for infection by diseases that kill millions
and sicken more than a billion people each year [...] Because of
their effect on human welfare and economic growth, deficient
water supplies and sanitation pose the most serious environmental
problems that face developing countries today". The magnitude
of the problem is apparent from the information in Annex 9.
Overall, "an estimated 25,000 people die every day as a result
of water-related sicknesses".
Water pollution problems are most serious in the urban
agglomerations of developing countries, where controls on
industrial emissions are not enforced and sewers, drains, let
alone sewage treatment plants usually are lacking. WHO estimates
that at least 600 million urban dwellers in the developing
countries live in what it terms "life- and health-threatening
homes and neighbourhoods". (It is worth remembering at this
juncture that the urban population of developing countries, now
1.7 billion strong, is expected to grow to 4.0 billion by 2025.)
Environmental health problems common to many neighbourhoods
include: "pools of dirty water, which accumulate around the home
because there are no drains or sewers, and house sites are
contaminated with excreta; pools of waste water [which can]
become a breeding ground for disease vectors; lack of drains will
often mean that floods are common occurrences and these bring
additional health problems".
The impacts of pollution carried by water streams also
include the damage done to fisheries, which are a major source
of proteins in many countries. This concerns inland as well as
marine fisheries, including fish nurseries in estuaries and
coastal mangrove swamps. Such impacts are enhanced by the already
large, and still growing, concentration of populations along sea
shores and rivers around the world.
The capacity of rivers to support aquatic life "is decreased
when the decomposition of pollutants lowers the amount of oxygen
dissolved in the water. [The effect] on fisheries may be
economically important. [A sampling of] monitoring sites in the
mid-1980s found that 12 percent had dissolved oxygen levels low
enough to endanger fish populations. The problem was worst where
rivers passed through large cities or industrial centers. In
China, only five of fifteen river stretches sampled near large
cities were capable of supporting fish. High-income countries
have seen some improvement over the past decade. Middle-income
countries have, on average, shown no change, and low-income ones
show continued deterioration".
The pollution of coastal waters is a factor in declining
catches in many areas of the developed and developing worlds.
Silt loads carried by rivers, aggravated by land development and
forest destruction, alter and reduce breeding grounds, and fish
are contaminated by sewage and toxic substances. In fact,
pollution from industry, farms and households that daily drains
into the sea imperils not only fish but the diversity of marine
life. Contrary to the popular view, oil spills and other effects
of shipping play a minor role in ocean pollution compared to the
impacts of human activities on land; sewage contributes about
half the polluting nutrients that enter the oceans worldwide, and
pollution from households also causes major harm.
Another widespread type of health problem is represented by
the impacts of water development through vector-borne diseases.
Hydrological changes brought about by dam construction and
irrigation development (larger, shallower or slower water bodies)
may cause significant increases in the extent and seasonal
duration of the breeding sites of mosquitoes and other vectors,
thereby increasing the transmission of malaria and other
diseases. Similar effects derive from the random creation of
water pools in third world cities, slums and industrial sites.
5. POPULATION-WATER LINKAGES IN A POLICY FRAMEWORK
5.1 Policy relevance of the linkages
Population-environment linkages are a development issue:
"[e]nvironment resources provide the basis for development, just
as environmental factors constitute part of the improvement in
the quality of life that development is meant to bring about".
Because of that, environmental variables must be part of the
analysis of development issues which influence population
dynamics. Likewise, population variables are relevant for the
analysis of environmental issues which may constrain overall
development. In practice, however, this convenient dichotomy is
useful only up to a point since actual issues involve both
population and development variables. Two major categories of
issues can be identified, namely:
- Water scarcity in a general sense, i.e. actual or
impending insufficiency of per caput resources, which may
constrain the development of an economic base; this also
constrains the well-being of the population and its very
growth, mainly through poorer health, higher morbidity and
mortality, and more intense out-migration than would
otherwise be the case.
By the same token, differential water availability
contributes to shape population distribution and prospects
for change in that distribution, in particular through
migration. This is of particular relevance in connection
with urbanization (which, as noted above, gives rise to an
acute concentration of demands for water): water supply
constraints must be considered when forecasting or planning
for urban growth. But the relevance for intra-rural
population flows and distribution should not be underrated:
for instance, caution should be applied with development
programmes that could cause excessive population
concentration in "beneficiary" areas.
- Water pollution, by affecting human health, has impacts
both on work productivity and on demographic variables that
determine population growth. It also affects animal health
and economic activities that depend on water supply of a
given quality. Overall, pollution has effects largely
similar to those of scarcity (inadequate water being
equivalent to lack of water), only with additional human
suffering.
Policy-wise, these issues can be analyzed and addressed on
various scales, from the country to the village level. Certainly,
population-water linkages can be considered at the national
level, where broad issues arising from overall levels of use and
sectoral competition can be identified (see section 4.1). This
broad picture is quite insufficient, however: both on the
population side and the development side, spatial distribution
and location aspects are essential for the identification of
problems and design of responses. Indeed, for action purposes
most natural resources and environment issues simply must be
dealt with at the local level.
The UNCED has aptly defined three programme areas where
attention to population aspects of environmental issues must be
applied. Two areas are relevant at this juncture, namely:
- "Formulating integrated national policies for environment and
development, taking into account demographic trends and factors";
- and "Implementing integrated environment and development
programmes at the local level, taking into account demographic
trends and factors".
National policies can set important principles and define
basic criteria for evaluating issues and designing programmes.
Decentralized levels of action, however, are probably more
important in view of the local specificity of environmental
problems. Some types of field programmes requiring attention on
account of population-water linkages, either because they are
heavily dependent on water resources or because they are liable
to affect these in a significant manner, are the following:
[i] proper attention to human health issues in policies and
projects involving water use and development, in particular
irrigation, water catchment and storage;
[ii] proper attention to migration and urbanization factors
in all forecasts made regarding water requirements,
including taking into consideration different consumption
patterns of households in different settings;
[iii] taking into account water needs, waste production and
ecosystem sustainability in formulating human settlement
policies;
[iv] and, of course, properly allowing for population
growth in all instances.
5.2 On analyzing population-water linkages
Let us see how population-water linkages can be analyzed
with the help of the classical equation:
I = P . c . i
where I is the total environmental impact of the consumption of
a given good, P is population, c is the per caput consumption of
that good and i is the impact per consumption unit. The equation
can be used with reference to two kinds of "impact", namely:
[a] the amount of a primary resource substracted as a result
of a unit consumption, or
[b] the amount of pollution resulting from a unit
consumption.
Both are clearly relevant for water issues.
5.2.1 Factors in water withdrawal
A - Domestic usages
In the case of domestic water use, c corresponds to water
consumption, and i to water withdrawal for domestic consumption
purposes; the two variables can be regarded as equivalent for our
purpose, although in all rigour withdrawals correspond to
consumption plus losses. The level of c varies a lot between
regions and countries (see section 2.1). It also varies among
population groups within countries, the main factor of variation
being the relative ease of access to water: distance to supply
point, mode of supply (well, pump, fountain...) and competition
at the supply point.
Population dynamics determines the growth and distribution
of basic needs for domestic water, rather than those of actual
consumption (or "demand"). It is thus the dominant factor in
developing regions, especially under arid and semi-arid areas,
while progress in supply development and technology for delivery
are increasingly decisive as one moves to more favourable
climates and more developed regions.
B - Agricultural usages
Agricultural withdrawals are a function of the need for
irrigation, that is--if abstraction is made of foreign trade--a
function of the excess of demand for agricultural products over
rainfed supply.
The level of consumption of agricultural products in
general, of foodstuffs, or of a particular item, can always be
expressed as the product of total population times per caput
consumption. Population growth has a variable part in the growth
of consumption, depending on the level of per caput consumption
already reached and the respective rates of growth of population
on the one hand and per caput income on the other. That part can
be estimated by the following calculation.
Assuming that the following growth rates have been observed
for a hypothetical country during a given period:
Population 2.1%
Per caput demand 1.0%
Total demand 3.1%
we shall estimate the contribution of population growth at
2.1/3.1 = 68%, and that of per caput demand at 1.0/3.1 = 32%.
(An application of this calculation was given in section 2.2.)
It should be noted that this calculation implicitly assumes
that the two factors are independent, i.e. that the rate of
population growth does not affect the rate of growth of per caput
demand or vice versa. This assumption is discussed below (D).
C - Industrial usages
Water withdrawals for industrial usages are a function of:
- total population,
- per caput consumption of the various industrial products (as
well as direct, private consumption of energy) and
- water withdrawal required (intermediate consumption plus
losses) for producing the quantity of each product (and
energy) consumed on average.
(There can be an I=Pci equation for every product consumed.)
Population is not a major factor in the growth of industrial
withdrawals: consumption levels (c) and technology (i) play the
major role--as can be inferred from the sectoral projections
reported earlier, which show the expected growth of industrial
water use to be vastly greater than expected population growth
in all regions (Annex 3).
D - On the ceteris paribus assumption
Hypothetical consequences of alternative courses of
demographic events for the environment are often estimated on the
basis of the I=Pci equation. Assuming that during a certain
period the impact of a particular consumption, I, has been
increased by 4 percent and P has grown by 2 percent, one might
argue that "had population grown by 1 percent only, the increase
in I would have--other things being equal, or ceteris paribus--
been limited to 3 percent".
But, can other things be assumed to be equal? The key point
in this case is: if population growth had been slower, would per
caput consumption still have grown at the same rate?
Per caput consumption of a given commodity # (c#) is a
function of: per caput income (y); the fraction of income that
is allotted to consumption expenditure (k); and the portion of
consumption expenditure that is allotted to commodity # (p#):
c# = y . k . p#
For the sake of simplicity let us assume here that k and p#
are independent from the population growth rate: this may not be
quite correct, at least for k, but the assumption is acceptable
because y is the major variable here. The question now boils down
to that of the effect of alternative population growth rates on
the growth of per caput income, and the answer does not hinge on
evidence but on theoretical stances.
Development theories of malthusian lineage hold that slower
population growth does not translate into slower GDP growth
(particularly in the short and medium run), and that it therefore
enables more rapid per caput income growth. In this framework,
if a hypothetical scenario with slower population growth is
compared with actual events (or another scenario) with faster
population growth, it should be admitted that reduced population
growth does not translate entirely into a reduced consumption.
By contrast, the opposite view--that a slower population
growth procures no gain in terms of per caput income growth--
implies that a deceleration of population growth brings about an
equivalent reduction in overall consumption--and, other things
being equal, in environmental impact.
It must be noted that the relevance of these considerations
varies from a consumption "sector" to the other. Domestic water
consumption, for instance, probably is not much affected by
income growth as such. As for demand for agricultural products,
two situations coexist: for the part which is met through
markets, the reasoning on per caput income applies; for the part
which is met through own-production, it does not.
5.2.2 Factors in water pollution
A - Domestic pollution
Domestic water is polluted solely by human wastage. Since
the level of per caput wastage is largely independent from
"affluence", population growth undoubtedly is the major cause for
growing emissions of polluting effluents. The impact of those
emissions depends on technology, in the form of water treatment
facilities. It must be noted that the efficiency of treatment
systems in turn is affected by a "workload" factor, i.e. the size
of population served per treatment unit. In developing countries
at least, investment in such facilities is constantly running
behind population growth, particularly in urban areas, leaving
most of the wastage untreated (see 3.3).
B - Agricultural pollution
Water pollution from agricultural activities is essentially
due to the use of chemicals (fertilizers and pesticides), mainly
in conjunction with irrigation. It might seem plain to say that
increase in that use is driven by growing demand for agricultural
products (see 5.2.1-B) in the face of difficulties for extension
of cultivation. This is largely true in developing regions, but
fertilizer use has been known to increase also in developed
regions, where such pressures are absent but economic factors may
push in the same direction.
The impact of population growth on the 1961-1988 increase
in fertilizer use (which is different from pollution, but related
to it), for major regions, has been estimated as follows:
Asian centrally planned economies: 15%
Developed countries: .............. 21%
Far East: ......................... 22%
Near East: ........................ 29%
Latin America: .................... 30%
Africa:.......... ................. 35%
C - Industrial pollution
Consistent with earlier notes on the role of population vis-
a-vis economic and technical factors in this sector, the impact
of population in this case in certainly weak.
5.3 Policy options
Two main policy problems are posed with regard to water
resources. One is to avoid major demand-supply imbalances during
the "planning period" under consideration. The other is to
minimize water pollution. Traditionally, the search for solutions
to these problems--especially the former--has focussed on
technology, much less on economic instruments and even less on
population variables.
In the analytical terms used earlier, minimizing total
environmental impact I can conceivably lead to tackle any or a
combination of the variables P, c and i: broadly speaking, the
problem is to weigh the merits of population programmes, economic
policies or technology policies. The options would include for
instance:
- slowing the growth of population or of a major consuming
group (in the case of sub-national areas, the idea of
diminishing population size through migration may
occasionally make sense);
- discouraging the consumption of the good in question,
possibly through substitution; and
- causing changes in the technology of production (or
shifting to external supply).
Admittedly, population policies will rarely be launched just
to facilitate the solution of an impending environmental problem.
Rather, detecting a conflict between population and supply trends
in a key sector such as water may be a strong additional reason
to consider such policies or to intensify them.
At an elementary level, when the level of basic services
(domestic supply and sanitation) is low, rapid population growth
means that it will be very difficult or impossible to improve the
situation rapidly. An inordinate amount of resources is needed
to ensure the basic necessities to additional populations and
"catch up" (i.e. provide for the unserved), leaving little or
nothing to invest in progress in services.
In other words, like in other areas, moderating population
growth serves at least to alleviate the growth of problems;
solving those problems is a matter of economic, social and
technological policies. Along this line, the view has been
expressed that "interventions to reduce rapid population growth
may be the most expedient means of preventing further
environmental degradation for one unfortunate reason: ultimate
causes are extremely resistant to change"; where this is the
case, population policies "can help to buy crucial time until we
determine how to dismantle more ultimate causes".
This assessment of the varying degrees of resistance to
change, among factors of environmental problems, has also been
questioned. Surely a case-by-case examination is necessary. At
any rate it can be said that stabilizing population in itself has
three effects, namely:
- moderate the growth of demand;
- moderate the growth of human waste; and
- ease time and space constraints so as to facilitate a
"sound development necessary to address problems of supply,
inefficient irrigation and waste disposal".
In various sectors, outlining and selecting among policy
options is carried out through scenario analysis. A typical
procedure for applying this method is:
(a) Construction of a "trend scenario", illustrating the
consequences of the mere continuation of existing trends.
(b) Assessment of the said scenario on the basis of
selected criteria and indicators; identification of
potential conflicts, negative changes and required
adjustments.
(c) Construction of alternative scenarios, simulating the
implementation of a range of possible policies to address
the issues identified.
(d) Comparative assessment of the alternative scenarios and
choice of one of them as "target".
Scenario analysis can be conducted in a variety of manners,
ranging from largely qualitative analyses to the use of full-
scale mathematical models of the system or sub-sector under
review. In the present case, it can be applied to compare the
merits of policies that address the population, consumption and
technical factors in water impact issues.
The issues ought to be identified both substantively
(supply, scarcity; quality, pollution; ...) and geographically,
i.e. in the context of specified areas. As to the merits of
possible policies, they have to do both with efficiency
considerations (the respective impacts of intervening variables)
and with cost considerations.
In effect, the debate on ways to address population
pressures on the environment often has left aside the latter
aspect. In its extreme version, the optimistic stand points to
the theoretical possibility of technological solutions (however
costly and problematic, e.g. the massive desalinization of
seawater) to deny the existence of long-term issues.
In reality, while sheer impossibilities may be rare,
situations leading to inordinate costs for maintaining the rate
of progress or even the status quo, are much more common. In
sound practice, the cost and efficiency of alternative policies,
including the impact of expected outcomes on the quality of life,
should be considered in all cases and decisions should be based
on the respective roles of the various factors in resource
exhaustion and pollution and the potential impacts (versus the
costs) of interventions on those factors.
In this context, technical variables do not suffice to
forecast outcomes and inform policies, and it is indispensable
to examine the social and economic context of fundamental
national or local decisions in matters of water management of
technology.
With regard to water resources, while one strand of thinking
emphasizes the relation between physical water supply and growing
human use as a constraint on development , another denies
fundamental incompatibilities and places hope (albeit cautious)
in the improvement of water management methods. In particular,
most recent technical meetings held by water scientists or
environment specialists at large do recognize population factors
in water issues, but tend to focus on technical and management
aspects in dealing with those issues: see Annex 10.
5.4 Knowledge base and research needs
Developing a better understanding of the relationships
between population dynamics, socio-economic development and water
(and related life support systems), in order to anticipate and
react to problems in a rational way, is an indispensable step in
formulating related policies. Population and development projects
could contribute to this end through their research components.
5.4.1 Research topics
Let us keep following the directions of Chapter 5 of Agenda
21 and define the basic purposes of research in this area with
reference to the objectives of the first programme area in that
chapter (on developing additional knowledge). The said purposes
would be the following (the language being adapted to the focus
on population-water linkages):
- To incorporate demographic trends and factors in the
analysis of water resources and development issues.
- To develop a better understanding of the relationships
among demographic dynamics, technology, cultural behaviour,
water resources and aquatic life support systems.
- To assess human vulnerability in hydrologically critical
areas to determine the priorities for action at all levels.
Once also adapted to the context of the substantive issues
at hand, the three lines of research identified in the same
framework in pursuance of these objectives will read as follows:
(A) Identify the interactions between demographic
processes, water resources and aquatic life support
systems.
(B) Integrate demographic factors into the ongoing study of
water resources change, to (i) study the human dimensions
of such change and (ii) identify vulnerable areas.
(C) Identify priority areas for action and develop
strategies and programmes to mitigate the adverse impact of
environmental change on human population and vice versa.
In brief, one will seek a better basic information on water
use patterns and the impacts of water supply problems on human
populations, and applications of that information in policy-
making. A research strategy could for instance include the
following types of studies and address the following questions:
1. Retrospective studies, geared mainly to provide the necessary
understanding of linkages between population factors, socio-
economic variables and water resources dynamics:
* What has been the influence of water resources and their
location on rural population distribution? On urbanization?
* What has been the impact of water resources development
on migration and settlements?
* What has been the impact of water resources development
on health and household wellbeing in the areas concerned?
* What have been the trends in water use by households and
their determinants (affluence-habitat-supplies...)?
* What have been the trends in water quailty? What are the
main factors in water pollution?
* What has been the impact of urbanization on local water
resources, their supply and quality?
* What have been the trends in water use by irrigated
agriculture and industry?
* Have specific areas experienced diminishing per caput
supplies, growing competition, conflicts over water and the
like?
2. Situation studies, i.e. cross-sectional assessments, geared
mainly to identify problem areas and populations at risk and
their problems:
* What is the current state of water supply (quantity and
quality) to households, their consumption patterns and
water-related health problems?
* What are the current water use patterns in irrigated
agriculture? In the main industries? Do they compete
locally with domestic usage?
* What are the current water-related health issues? What is
their prevalence? Are they on the increase or on the
decline?
* What population groups appear to be at disadvantage with
regard to access to water, on account of their geographic
location? of their socio-economic status? of other social
variables?
3. Perspective studies, geared to scenario analysis and more
generally to detect potential inconsistencies and explore
policies.
* What could be the impact of planned agricultural and
industrial development projects (with specific regard to
their location) on water supply for household usage?
* What could that impact be on population redistribution
through migration and subsequent changes in domestic
demand?
* What are the prospects for scarcities and other supply
problems (quantitative and qualitative) at the local level?
* In particular, what are the implications of urbanization
trends for water competition?
* Conversely, can constraints be detected that may
invalidate trend projections of urbanization and limit
urban population size? or the urban growth rate?
* Are there areas where foreseen water supply problems are
so serious that spontaneous or planned relocation of
population and/or economic activities must be envisaged?
* By contrast, in what areas can water problems be
classified as tractable? What policies options can be
recommended to deal with them?
* How will population dynamics (growth, urbanization etc.)
affect intersectoral and intra-sectoral competition for
water? How would the conceivable alternative outcomes of
that competition in turn affect population dynamics?
* How might the explicit or implicit water use policies
affect population dynamics?
5.4.2 Indicators
A variety of indicators will obviously be needed to study
water use and requirements in the relevant degree of detail--such
as water use per caput, per unit or ton of industrial product,
per unit of energy produced or per ton of agricultural commodity
produced, per unit area, per unit value added and so on. More
indices will have to be devised on an ad hoc basis. One possible
approach to the exploration of potential imbalances between
population and resources, for instance, is to assess the specific
"carrying capacities" of relevant areas with due attention to
critical resources and ecosystem sustainability. Estimates of the
population which the water resources of a given area could
support (under a range of assumptions regarding sectorial water
use) could be used among others.
The scale of investigation should be disaggregated as
appropriate. On supply issues, we have seen that the area for
analysis should be "relatively small [since] summation of supply
over large areas obscures nonuniformity in distribution and
therefore presents an overly optimistic impression of supply
adequacy". Analyzing population-resources issues in the
context of the watershed is a recent and useful proposal. But
other issues justify similar care in selecting the study unit:
for instance, health issues often are location-specific. While
both rural and urban problems must be assessed and addressed,
focus must be placed on urban communities in the sense that the
major ones must be treated as separate "individuals".
The issue of water as a general constraint on development,
for want of sufficient information, so far has been approached
through indices describing no more than the "density" of
population relatively to water resources (the Population/Flow
Unit indicator: see 4.1). Working from actual actual use levels,
with some spatial disaggregation, would be a major improvement:
for policy purposes, it is essential to determine which economic
sectors, geographic areas or groups are at risk of water
scarcity.
Distributional dimensions--referring to groups within the
population of a given geographic area--are extremely important.
Those dimensions modify the usual risk considerations in critical
ways, since unequal distribution can imply severe shortages for
some groups, even though aggregate indices do not indicate
overall scarcity. And they will point to problems that
generally require more than technical solutions.
In general, data on water resources and use still are
insufficient, as underlined by the International Conference on
Water and the Environment held in Dublin in 1992 and other
meetings. Certainly many elements of information will have to be
collected through field surveys. In many cases the classical
surveys of the demographic or socio-demographic type could be
extended to cover the issues covered here.