Pergamon Phys. Chem. Earth (B), Vol. 26, No. I I-12, pp. 869-876,200l

0 2001 Elsevier Science Ltd

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1464-1909/01/S - see front matter

PII: S1464-1909(01)00099-S

PODIUM: Projecting Water Supply and Demand for Food Production in 2025

C. de Fraiture, D. Molden, U. Amarasinghe and I. Makin

International Water Management Institute, PO Box 2075 Colombo, Sri Lanka

Received 24 May 2000; accepted I2 February 2001

Abstract

Since 1997, IWMI has been developing models to investigate future food and water requirements. Since the initial results were published (Seckler et al., 1998), the data and methodologies were refined substantially, evolving into the PODIUM model. The model estimates projected increases in water demand in 2025 resulting from the expected population growth and changes in consumption pattern, for individual nations. The PODIUM model provides a user-friendly means to analyze alternative future scenarios and conduct sensitivity analysis.

As part of the World Water Vision 2025 exercise, the PODIUM model was used to test a range of scenarios related to food and water demand. In the IWMI base scenario, 33 percent of the population of the studied countries will face absolute water scarcity. These countries will not have sufficient water resources to meet water needs. Another 45 percent of the population live in countries that will face economic scarcity. Countries in this category may not have the capacity or financial resources to develop sufficient water resources. Globally, water diversions to agriculture will grow by 17 percent. Fifteen countries, mainly in the Middle East and Africa, will rely on cereal imports for more than 25 percent of their grain consumption (Seckler et al., 2000).

This paper presents the modeling strategies adopted in the PODIUM model and the results obtained during the development of the World Water Vision (Rijsberman and Cosgrove, 2000). These results indicate the need for substantial investment in water resources development, improving agricultural water use and expansion of both irrigated and rain-fed agriculture.

0 2001 Elsevier Science Ltd. All rights reserved

1. Background

In recognition of the increasing concerns regarding the future of water resource management, the International Water Management Institute (IWMI), previously known as the International Irrigation Management Institute (IIMI),

Correspondence to: C.D. Fraiture. International Water Management Institute, P 0 Box 2075, Colombo, Sri Lanka

has expanded its research to encompass irrigation in the context of water basins. This expansion of research focus

has led to the development of the “IWMI Paradigm” (Perry, 1999). In essence, the IWMI Paradigm calls into question the value of irrigation efficiency as the primary measure of system performance (Seckler, 1996) by explicitly including the utilization of return flows. Whilst, in itself, the analysis of return flows was not original, the IWMI Paradigm provided the framework for development of water accounting in irrigated basins (Molden, 1997) and subsequently the analysis of water supply and demand predictions for the first quarter of the twenty-first (Seckler et al., 1998; Seckler et al., 2000).

Work on the development of models for estimating water supply and demands for the year 2025 started in 1997. The conceptual framework is a water balance implemented at national scale. These models are described in detail by Seckler et al. (1998) and have been used to compare water supply and demands at country level. The models predict water scarcity, described by two factors: required percentage increase in water diversions between 1995 and 2025; and the projected 2025 water diversions expressed as a percentage of utilizable water resources (Seckler et al., 1998). Physical

water scarcity is defined as annual water diversions of more than 60 percent of the utilizable water resources, and economic scarcity is defined as future water withdrawals greater than 25 percent more than 1995 levels, implying the requirement for enormous investments to develop the additional water resources required.

Water scarcity can be defined either in terms of the existing and potential supply of water, or in terms of the present and future demands or needs for water, or both. For example, in their pioneering study of water scarcity, Falkenmark, Lundqvist, and Widstrand (1989) take a “supply-side” approach by ranking countries according to the per capita amount of “Annual Water Resources” in the country, referred to as AWR by Seclcler et al. (1998). Falkenmark et al. define 1,700 cubic meters (m3 ) per capita per year as the level of water supply above which shortages will be local and rare. Below 1,000 m3 per capita per year, water supply begins to hamper health, economic development, and human well-being. At less than 500 m3 per capita per year, water availability is a primary constraint to life. IWMI refer to this as the “Standard” indicator of water scarcity among countries since it is by far the most widely used and referenced indicator (e.g., Engelman and Leroy, 1993).

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870 C. de Fraiture et al.: PODIUM: Projecting Water Supply

Another supply-side approach is taken in a study commissioned by the UN Commission on Sustainable Development (Raskin et al., 1997). This study defines water scarcity in terms of the total amount of annual withdrawals as a percent of AWR. We refer to this as the “UN” indicator. According to this criterion, if total withdrawals are greater than 40 percent of AWR, the country is considered to be water-scarce.

One of the problems with the supply-side approach is that the criterion for water scarcity is based on a country’s AWR without reference to present and future demand or needs for water. The original study by Seckler et al. (1998) and the subsequent work that led to the development of PODIUM attempt to resolve these problems by simulating the demand for water in relation to the supply of water over the period 1990-2025. We have adopted the approach of analyzing alternate development scenarios, making assumptions about water use in agriculture, domestic and industrial sectors.

Seckler et al. (1998) considered two scenarios where the difference between the scenarios was due to different assumptions about the effectiveness of the irrigation sector. The first scenario presents a “business as usual” base case; the second scenario assumes a high, but not unrealistic degree of effectiveness of the irrigation sector. This study presented estimates of how much of the increase in demand for water could be met by a more effective use of existing water supplies in irrigation and how much would have to be met by the development of additional water supplies. These estimates were then compared with the AWR for each country to determine if the nation’s water resources would be sufficient to meet its needs for additional water development.

2. PODIUM

The PODIUM model is designed to provide a user-friendly interface for policy makers, scientists and others to interact in developing alternative water scenarios using a consistent framework of data and analysis. Because of its flexible and transparent structure it is a suitable tool to explore scenarios and analyze the complex interplay of the many variables that determine water supply and demand issues. Our objective in developing PODIUM was not to create a deterministic model that makes projections, but rather to develop an interactive tool that supports the user in exploring the implications of varying assumptions and hypotheses. At present, PODIUM is calibrated for 45 countries that represent the major regions of the world and over 80 percent of the global population.

One of the main features of the PODIUM model is that all variables and assumptions are explicit and can be changed easily by the user. This makes the model an excellent tool for scenario testing. PODIUM can be applied at any scale- country, basin, subbasin, or global. For the global projections, PODIUM aggregates results country by country to the global scale. Applications at country level have been used in the analysis for the Vision 2025 exercise because policies about food and trade are made on a country basis. IWMI currently has PODIUM in two versions: the country-

level model and the global-level model. The country-level analysis is chosen as the basic unit of analysis as opposed to the water basin. Although this might be less satisfactory from a hydrological point of view, it is nations not river basins that make policy.

Country Model

The objective is to provide a tool to raise policy makers’ awareness concerning future food and water requirements and water scarcity. The model assists policy makers in analyzing the quantitative aspects of future food and water demands and allows them to test user-defined scenarios, which could form the basis of policy formulation. Being developed for decision makers-not necessarily for experts in computer programming-the model has a very user- friendly interface and a transparent structure. The country model also proved useful for educational purposes.

The model computes the increased food and water requirements for 2025 based on user-defined scenarios describing alternate future diets and developments in agriculture. The current situation (base year 1995) is defined by data extracted from international databases such as AGROSTAT (FAO, 1997), World Resources Institute (WRI, 1998), and the United Sates Department of Agriculture (USDA, 1994). Climate data are derived from the IWMI World Water and Climate Atlas (http://www.iwmi.org).

Global Model

The global-level model is a Microsoft Excel spreadsheet used for aggregating country-level analyses into global or regional groups. The results from the country model are entered into the global model as they become available.

2.1 Model Structure

PODIUM is structured as four interconnected modules:

l The first module estimates national food requirements in 2025 based on assumptions about population growth rates, daily per capita calorie intake and the composition of diets.

l The second module computes the projected national food production based on expected yields and cultivated area under both irrigated and rain-fed conditions. Projected production is compared graphically with the required production computed in the first module. The user adjusts assumptions and development options iteratively to match requirements with production and, if necessary, imports of cereals.

. The third module converts the projected national food production into equivalent water demand making allowances for water use efficiency and recycling.

. The final section calculates the expected domestic and industrial water use based on income growth projections. The total water requirements for food

C. de Fraihm et al.: PODIUM: Projecting Water Supply 871

production and domestic and industrial use are Multiplying the renewable water resources by the

summed and compared with the base year (1995) utilization factor (PDF) results in the utilizable water supply,

actual water diversions. the upper limit of water availability.

Figure 1 illustrates the components of the first three modules. Data and assumptions are explicit and can be changed easily by the user. Annex A summarizes the principal variables and basic equations employed in the PODIUM model. PODIUM is explorative in character rather than predictive. The model does not produce definitive predictions but rather enables analysis of “what-if’ questions to explore scenarios.

A major constraint in global studies concerning water supply and demand is the reliability of data in international databases. In PODIUM, the user is encouraged to review the default data for 1995 and revise as required from local knowledge or improved data sets. An extensive use of graphics to present results allows the user to monitor the effects of these changes, thus enhancing the use of the model for scenario testing and sensitivity analysis.

2.3 Primary Water Supply Versus Total Diversions

In many studies total water use is estimated by the summation of all diversions for individual uses (total withdrawals for domestic, industrial and irrigation sectors). This leads to an overestimation of water use as this disregards the fact that drainage flows are often reused by other users downstream. Drainage water in irrigation results from:

. Seepage from conveyance systems, l Deep percolation below the root zone, and l Surface runoff from fields.

2.2 Annual Renewable Water Resources and Utilizable Water

The World Resources Institute (WRI, 1998) and other centers (Shiklommanov, 1997,1999) publish estimates of annual renewable water resources for most countries in the world. These annual water resources estimates have two components: water resources generated within the national boundaries; and river and groundwater flows originating in neighboring countries that flow across the national boundaries. The source of internally generated resources is precipitation that is converted into either surface runoff, or subsurface flows that replenish groundwater. Annual water resources are used in many studies as an indicator of the water available to a country. However, it should be noted, that not all water generated by precipitation is available for use. In monsoon climates, for example, the bulk of precipitation occurs during high intensity storms during short periods of the year generating high river flows. Much of the rain will be discharged back to the oceans without being captured or stored for later use. In flat coastal areas opportunities to store rainfall are also limited.

To account for the difference between annual water resources and potentially utilizable resources, we have definedthe ‘potential utilization factor’ (PDF). This factor is estimated by an evaluation of the seasonal and inter-annual variability of precipitation and available potential for storage. The global weighted average utilization factor is estimated as approximately 36 percent, although the majority of countries have utilization factors of around 60 percent, and in dry areas up to 85 percent. The low global average is due to the influence of large rivers in Brazil and Bangladesh and monsoon floods, such as in India. The Central Water Commission of the Government of India estimates that only 38 percent of the annual water resources reported by Shiklomanov (1997) is actually potentially utilizable.

Drainage water may flow to saline areas or to oceans where the water is effectively lost to immediate human use. On the other hand, drainage water may flow back into the river or infiltrate to shallow groundwater where it can be captured and reused beneficially. This is the return flow of water. For example, in areas of paddy cultivation, irrigation water often flows from field to field; and seepage losses replenish shallow groundwater that is later extracted for irrigation during the dry season. Releases from hydroelectric plants are frequently used for downstream irrigation; and municipal return flows, for example Mexico City, are used to support extensive areas of irrigated vegetables. Thus in many cases, because of recycling, drainage from apparently ‘inefficient’ users may become another user’s water supply.

In the PODIUM model we have introduced the concept of ‘primary water supply’ defined as total diversions to all sectors, less the volume of diverted water that leaves the model domain (Basin or country). Primary water is an important concept in that it defines the upper limit of the volume that can be depleted by various uses. Because of recycling, total diversions are, in general, larger than the primary water supply. In some circumstances, the total diversions may even exceed the total utilizable water resources of a country.

2.4 Evaporation Factor

Obviously not all the primary water supply is actually consumed or evaporated. For example hydropower diverts large volumes of water, but only water evaporated from storage reservoir is lost for further use whilst the major proportion flows back into the system. In irrigation schemes a larger proportion of the diverted water is evaporated by plants and open water bodies, but again a significant volume often returns to the river or percolates to groundwater and is thus available for further diversion and use.

The evaporation factor is defined as the fraction of primary water supply that is evaporated. This concept could be applied at the scale of individual basins (referred to as ‘basin efficiency’) however in this study we consider the

812 C. de Fraiture et al.: PODIUM: Projecting Water Supply

evaporation factor at country level. Hence, the country evaporation factor expresses the fraction of the primary water supply at country level that is evaporated by domestic, industrial, agricultural, and other uses such as open water surfaces, and nonagricultural vegetation.

2.5 Constraints

PODIUM applies the following constraints to evaluate water use in each country studied:

A. Country Evaporation Factor In theory, the Country Evaporation Factor could reach a maximum of 100 percent if all primary water was evaporated through either beneficial and non-beneficial use. However, in practice this is neither achievable and, more importantly, not desirable for environmental reasons. Operation of irrigation schemes deposits salts, agrochemicals and other pollutants that need to be flushed out. Further, in many areas seepage from irrigation and other uses is a major source of water recharging aquifers that are used for domestic supply.

In the water supply and demand scenarios discussed here, the Country Evaporation Factor is constrained to less than 70 percent, i.e,. a maximum of 70 percent of all primary water diversions may be evaporated by the different water use sectors. The balance, 30 percent, is considered as the minimum necessary to avoid environmental hazards such as salt and pollutant build-up and groundwater table decline.

B. Degree of Development Theoretically, a nation could divert all the utilizable water resources to industrial, domestic and agricultural sectors. However, this is neither practical nor desirable. Firstly, some minimum flows should be retained in the rivers to maintain ecological and environmental conditions. In many cases, minimum flows are required for navigation and fishing purposes. Allocations for environmental uses (natural forests, wetlands, swamps, lakes and wildlife) are increasingly becoming an important issue and a focus of public debate and attention.

To measure the extent of diversions we have defined the “Degree of Development” as primary water supply divided by utilizable water resources. This leads to the definitions of water scarcity.

2.6 Indices of Water Scarcity

In this study, a country is considered to have a physical water scarcity if the degree of development exceeds 60 percent. At this level of development, 40 percent of the utilizable water resources is retained for other sectors such as navigation, fisheries and environment. It should be noted that some water-scarce countries exceed the 60 percent limit considerably, even in the base year, due to the unsustainable use of groundwater.

Countries facing physical water scarcity will not have sufficient water resources to meet their agricultural, domestic and industrial needs in 2025, whilst maintaining acceptable

environmental and other in-stream uses. Even in the present situation, many of these countries cannot meet their needs. It would appear that the only option for these countries is to invest in desalinization plants and/or to reduce the amount of water used in agriculture, reallocating the water released from agriculture to the other sectors. This will lead to increased dependence on imported food.

A country is considered to have an economic water scarcity if it is to increase its water supplies by development of additional storage, conveyance and regulation systems equivalent to more than 25 percent of the 1995 levels. Many of these countries may have sufficient physical water resources but may lack the financial resources and capacity to develop these.

3. Limitations of the Model

Working with international databases has exposed gaps in the data available. For example, the lack of separation of recorded areas and yields of irrigated and rain-fed agriculture. Furthermore, the data available in public domain international data sets are frequently less accurate than locally available information from which they were derived. Refining the data inputs required for the model by reference to local experts, data sources and by using other simulation models to verify or refine reported data has proved to be a continuous process in the development and application of PODIUM.

In the present form, the PODIUM model is focussed on cereal crops. In the Asian context this gives satisfactory results as a major proportion of the diet is derived from cereals; and most irrigated land is devoted to cereal crops. However, to adequately reflect food consumption and cropping patterns in the Middle Eastern and African countries, IWMI is currently expanding the model to allow for a wider mix of food crops, including vegetables and root crops.

PODIUM takes a country as the basic unit of analysis. As a result, the model disregards spatial variations that exist within countries. This is particularly evident for large countries like India and China and may lead to inaccuracies in the projections. At present IWMI is working on disaggregating the larger countries in smaller units, to account for the spatial variations within these countries. Amarasinghe et al. (1999) have illustrated these variations in their study of Sri Lanka, identifying seasonal and spatial differences in the severity of water shortages.

4. Application

IWMI applied the PODIUM model to formulate an initial vision for 2025. This scenario referred to as IWMI’s base case scenario, predicts that 33 percent of the population of the studied countries will face physical water scarcity in the year 2025. These countries will not have sufficient water resources to meet water needs. Another 45 percent of the

C. de Fraiture et al.: PODIUM: Projecting Water Supply 873

population will live in countries that will face economic scarcity where the capacity or financial resources are likely to be insufficient to develop sufficient water resources. Globally, water diversions will grow by 22 percent. Fifteen countries, mainly in the Middle East and Africa, will rely on imports for more than 25 percent of their grain consumption (Seckler et al., 2000).

During 1999, PODIUM was presented and utilized at meetings attended by national planners and policy makers in India, Sri Lanka, Nepal and Morocco.

PODIUM was used during the eight regional consultative meetings organized as part of the Vision 2025 exercise to provide a quantitative basis for discussions about future water and food demand issues. Additional information on the Vision 2025 exercise can be obtained at http:\\watervision.org. The model was effective in the identification of critical issues which required further debate, and research. Further the model was used to provide a quantitative basis for the scenarios formulated by

the Scenario Panel of the World Water Vision 2025 exercise (Rijsberman, 2000) summarized below.

4.1 World Water Vision 2025 Scenarios

In developing the Vision 2025 presented at the Second World Water Forum in the Hague, (March 2000) three scenarios were formulated to guide the process. These were:

. Business as Usual-a continuation of current policies.

. Technology, Economics and the Private Sector (TECHNOLOGY)-where research and development are led by private sector initiatives, but the poorest countries are likely to be left behind.

. Values and Lifestyles (VALUES)-focusing on sustainable development with an emphasis on research and development in the poorest countries.

Waterforfiod was a significant area of the discussions that led to the Vision 2025. PODIUM was used, with other models to investigate the impacts of population growth, irrigated area expansion, yield growth and improvements in irrigation efficiency on the probable requirements for additional water resource developments under these different scenarios.

Water Supply and Demand Scenario Conclusions

Figures 2 & 3 illustrate the results of the PODIUM simulations of the Vision 2025 scenarios by the major country groupings. From the detailed results presented elsewhere (Seckler et al., 2000) it is clear that:

l The Business as Usual scenario will lead to substantial cereal deficits at global level and most likely to decreased calorie intake in low-income developing countries.

l The TECHNOLOGY scenario food supply is sufficient but the gap between OECD and low-income developing countries widens. Many countries stretch their water resources to the limit, sometimes leading to environmental problems.

. The VALUES scenario production is sufficient and the gap between OECD and low- income countries reduces, although it is still far from closed. Adverse environmental impacts are kept to a minimum. This scenario requires considerable developments of water related infrastructure to increase available water supply, in low-income countries. This will require enormous investments in the water sector.

5 . Conclusions

It is widely recognized that many countries will be entering an era of severe water shortage over the next few years. The International Water Management Institute (IWMI) has a long-term research program to determine the extent and depth of this problem, its consequences to individual countries, and what can be done about it. As Seckler et al. noted in1998 “We assumed that this would be a rather straightforward exercise of projecting water demand and supply for the major countries in the world over the 1990 to 2025 period. But as the study progressed, we discovered increasingly severe data problems and conceptual and methodological issues in this field”. PODIUM developed from our need to have a simulation model that is based on a conceptual and methodological structure that we believe is valid. To be useful, the model had to be flexible and robust to accommodate various estimates and assumptions about key parameters when data are either missing or subject to a high degree of error and misinterpretation.

The model is in a spreadsheet format and is made as simple and transparent as possible so that others can use it to test their own ideas and data. One of the strengths of the PODIUM model is the inclusion of a more thorough treatment of the irrigation sector than any other used to date in this context. Since irrigation uses over 70 percent of the world’s supplies of developed water, getting this component right is extremely important.

This paper presents the modeling strategies adopted in the PODIUM model and the results obtained during the development of the WWC Vision. These results indicate the need for substantial investment in water resources development, improving agricultural water use and expansion of both irrigated and rain-fed agriculture. The PODIUM country scale model is available at IWMI’s website (http:// www.iwmi.org). IWMI welcomes other researchers and practitioners to utilize the model in their studies; and to update and improve on the data sets provided.

874 C. de Fraiture et al.: PODIUM: Projecting Water Supply

References

Amarasinghe, U. A.; L. Mutuwatta; and R. Sakthivadivel 1999. Water scarcity variations within a country: A case study of Sri Lanka. Research Report 32. Colombo, Sri Lanka: International Water Management Institute.

Engehnan, R.; and P. Leroy. 1993. Sustaining water: Population and the future of renewable water supplies. Population and Environment Program. Washington, D. C.: Population Action International.

Falkenmark, Malin; Jan Lundqvist;, and Carl Widstrand. 1989. Macro-scale water scarcity requires micro-scale approaches: Aspects of vulnerability in semi-arid development. Natural Resources Forum 13 (4): 258-267.

FAO (Food and Agriculture Organization). 1997. FAOSTAT statistical database in CD-ROM. Rome: FAO. Molden, D. 1997. Accounting for water use and productivity. SWIM Paper

1, Colombo, Sri Lanka: International Irrigation Management Institute.

Perry, C. J. 1999. The lWMI water resources paradigm. Definitions and implications. Agricultural Water Management 40(1):45-50. Raskin, P.; P. Gleick; P. Kirshen; G. Pontius; and K. Strzepek. 1997. Water

futures: Assessment of long-range patterns and problems. Stockholm, Sweden: Stockholm Environment Institute.

Rijsberman, F. 2000, Water world scenarios analyses Working Draft 25& February. Vision Management Unit. Paris: UNESCO.

Rijsberman, F.; and W. J. Cosgrove 2000. Making water everybody’s business. London, UK: Earthscan Publications Limited.

Seckler, D. 1996. The new era of water resources management. Research Report 1. Colombo, Sri Lanka: International hrigation Management Institute (BMI).

Seckler, D.; Upali. A. Amarasinghe; David Molden; Radhika de Silva; and Randy Baker. 1998. World water demand and supply 1990 to 2025: Scenarios and issues. Research Report 19. Colombo: International Irrigation Management Institute.

Seckler D; , D. J. Molden; UAmerasinghe; and C de Fraiture. 2000. World water supply and demand 1995 to 2025. Chapter 15. In. Waler world scenarios analyses, ed. Rijsberman F. Working Draft 25” February. Vision Management Unit.

Shiklommanov, I. A. 1997. Assessment of water resources and water availability of the world. World Meteorological Organization. (Duplicated).

Shiklommanov, I. A.. 1999. Personal communication. Data prepared for the World Commission on Water. Duplicated.

UN (United Nations). 1999. World population prospects, 1998 Revision. New York: UN Department for Policy Coordination and Sustainable Development.

USDA. 1994. Major world crop areas and climaric projles. Washington, DC, USA: USDA. xii, 279~.

WRI (World Resources Institute). 1998. World resources 1998-99. A guide to the global environment. New York: Oxford University Press.

Annex A - Definitions used in computation of water scarcity indices

(1) E’L,,=E’L*K, (2) P,e = 0.8 * P,s (3) NET = ET,r - P,s

where, ETcmp = Crop evaporation P,e = Effective rain P7s = 75% probable rainfall NET = Net irrigation requirements

(4) (5)

TDti = (NET + P)/IE TD=TD&i+TDb,+TD&j

where, TD = Total diversions (all sectors) TDti = Total diversions for irrigation

TD&,= Diversions for domestic sector TDti = Diversions for industrial sector

IE = Classical irrigation efficiency P = Percolation

PWS=E+O E=NET+hb+EQm+Eind

Edom = mdcm * EFdm

Ebd = T&d * EFtr,,, R=TD-PWS M=TDIPWS

where, PWS = Primary water supply E = Total evaporation

0 = Outflow to sea or downstream countries E,,b = Non-beneficial evaporation E do,,, = Evaporative use in domestic sector Eind = Evaporative water use in industrial sector EF&, = Evaporation factor in domestic sector EFti = Evaporation factor in industrial sector R = Recycled water; M = Multiplier

UWR=RWR*PUF EFmmvy = E I PWS DOD = PWS / UWR

where, UWR = Utilizable water resources RWR = Renewable water resources

PUF = Potential utilization factor DOD = Degree of Development Ef,,, = Country level Evaporation factor

C. de Fraiture et al.: PODIUM: Projecting Water Supply 875

Iodule 1: Cereal requirement variables

Diets

Iodule 2: Cereal production variables

Iodule 3: Water requirement variables

: I. . .

) TOW Im~tlon

Dlvorslons for Divorshns for domostio

dlwrsions (TD) hdustri~l

4 \

Prlmsry Dlwrsions (RWS) - - ” - .- .__._,,,

,,

Fig. 1. Schematic of PODIUM model structure.

816

60%

C. de Fraiture et al.: PODIUM: Projecting Water Supply

Domestic and industrial diversions as percentage of total diversions

1995 BAU TEC VAL

0 OECD countries

n High income developing countries

n Low income developing countries

Fig. 3. Summary of vision 2025 simulations-domestic and industrial diversions.

Cereal deficit/surplus as percentage of total cereal consumption

1995 BAU TEC VAL

30.0%

20.0%

10.0%

0.0%

-10.0%

-20.0%

-30.0%

-40.0%

q OECD countries

n High income developing countries

n Low income developing countries

Fig. 2. Summary of vision 2025 simulation-cereal production.