UN Population Division, Department of Economic and Social Affairs,
with support from the UN Population Fund (UNFPA)

Population and Water Resources (contrib. by FAO)


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


                Population and the environment:

                a review of issues and concepts

                for population programmes staff



                        September 1994


     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


     -  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


     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



1. INTRODUCTION                                         4


     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


     3.1 Impact on surface water                        9

     3.2 Impact on groundwater                         10

     3.3 Water pollution                               11


     4.1 Water scarcity                                13

     4.2 Water pollution                               16


     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



               "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."


     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


     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).


2.1 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


                               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


      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.


     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


     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


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


     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. 


4.1 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


     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




     < 100     Cameroon    Sierra Leone








   100-600     Angola      Botswana    Mauritania

               Chad        Ghana       Namibia

               Cote-d'Iv.  Mali        Niger

               Zaire       Sudan       Senegal


Water stress               Benin       Ethiopia

 (600-1000)                Burkina F.  Uganda



Water scarcity             Tanzania    Nigeria     Algeria

(1000-2000)                Togo                    Egypt

                           Zimbabwe                Lesotho




Water barrier              Malawi                  Burundi

   (> 2000)                                        Kenya




     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


     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.


5.1 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


     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


     [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


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


     - 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


     (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


     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


     (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


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


     * 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


3. Perspective studies, geared to scenario analysis and more   

   generally to detect potential inconsistencies and explore   


     * 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


     * 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


     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.

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