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Towards measurable criteria for the equitable sharing of international water resources
Water Policy 4 (2002) 19–32
Towards measurable criteria for the equitable sharing of international water resources Pieter van der Zaag*, I.M. Seyam, Hubert H.G. Savenije IHE Delft, P.O. Box 3015, 2601 DA Delft, The Netherlands Received 18 February 2001; received in revised form 11 September 2001; accepted 16 December 2001
Abstract Equity is key to the allocation of international water resources. Six possible criteria and allocation algorithms that operationalise the equity concept, are developed and applied to the Orange, Nile and Incomati rivers. The criterion that considers all (blue and green) water resources and that uses the basin population as the main allocation variable yields the most equitable water allocation. Two important variables are identified over which the riparian countries should reach consensus:
1. The value of green water relative to blue water. 2. The fraction of reserved water, which is defined as the basic entitlement of each riparian country. These findings are based on approximate data and have therefore a limited validity. With this caveat it is suggested that the approach developed in this article may help de-politicise negotiations between riparian countries and provide fresh perspectives that may unlock stalemates during negotiations. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Allocation algorithms; Equity; Green water; Incomati river; International water resources; Nile river; Orange river; Water allocation; Water law
1. Introduction The United Nations Convention on the Law of the Non-Navigational Uses of International Watercourses, adopted by the General Assembly in 1997, provides a framework for negotiations between countries sharing an international water resource. The convention defines the obligation *Corresponding author. IHE Delft, PO Box MP 600, Mount Pleasant, Harare, Zimbabwe. Tel.: +263-4-336-725; fax: +263-4-336-740. E-mail address: [email protected] (P. van der Zaag). 1366-7017/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 1 3 6 6 - 7 0 1 7 ( 0 2 ) 0 0 0 0 3 - X
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not to cause appreciable harm and the right to reasonable and equitable use as co-equal criteria for the allocation of water between riparian countries (McCaffrey, 1998, Chap. 2). These principles have to be translated into concrete agreements through negotiations between the countries involved. Some authors have argued that the principle of equity is key to water allocation (Wouters, 1997; Wolf, 1999), which was also the premise of the 1966 Helsinki Rules (McCaffrey, 1993, Chap. 8). The principle of reasonable and equitable use (Article 5 of the UN Convention), however, is defined in general terms, and is thus prone to subjective interpretation. Postel (1992, p. 189) has argued that clearer criteria are needed. This paper attempts to define measurable criteria on the basis of which water resources can be allocated to the riparian countries in an equitable manner. Such measurable criteria may facilitate negotiations between riparians that are in conflict over the issue (Seyam, 1999). In fact, jointly defining such criteria could be a central activity during negotiations. The paper does not take into account criteria other than that of equity. Once equitable water allocations have been agreed upon, riparian countries may jointly decide to transfer water from one to another, for instance against compensation (in the spirit of Article 7 of the UN Convention). Since you can only sell something that belongs to you, the rights of the riparian countries sharing a common water resource have to be established before economic or financial transactions concerning water allocation can occur. Deciding to let market forces play a role in the (re)allocation of water resources or not should therefore be a secondary issue. The paper consists of three parts. The first part defines six possible criteria and algorithms for the equitable allocation of water resources, using the Orange river (known as Senqu river in Lesotho) as an example. The criteria take into account, on the demand side, the number of countries sharing the water, the basin areas of each riparian country, and the riparian population. On the supply side, the criteria consider ‘blue’ water and ‘green’ water (Falkenmark, 1995). Blue water is renewable water that occurs in rivers and aquifers. Green water is renewable water that occurs in the soil; it is the part of the rainfall that infiltrates into the root zone and is directly used by plants for biomass production through transpiration. Green water is a very important resource for agricultural production, which is generally overlooked in water resources assessment. The second part of the paper applies some of the criteria to the Nile and Incomati (or Komati) rivers. The third part of the paper provides some ideas for refining the approach. The suggestions made in this paper are exploratory and conceptual. They are meant to stimulate critical thinking about the problem of sharing the waters in an international river basin.
2. Possible criteria for the equitable sharing of international water resources 2.1. Surface water, equally shared among countries The simplest and most straightforward criterion for the equitable sharing of international waters may be formulated as: Criterion 1: All surface waters generated in an (international) river basin should be shared by the riparian countries equally (as far as possible).
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To operationalise this criterion it should be accepted that it is not possible to pump water from down- to upstream countries (hence the addition: as far as possible). That is the reason why the proposed procedure is not just to split the available water equally. The procedure moves from upstream to downstream whereby at each border crossing the remaining water is shared equally among the downstream countries. It is further assumed that a certain fraction Rb of the surface water generated in each riparian is ‘reserved’ for that country, and remains outside the negotiations. This ‘reserve’ may be used for primary water requirements of the basin population and for the water requirements of riverine ecosystems. To further operationalise criterion 1, the following steps are proposed: 1. Assess for each of the basin countries the amount of blue water generated in that country. In this paper, we estimate the blue water component using Eq. (A.1) (Appendix A), as proposed by Savenije (1997). 2. Subtract the ‘reserved’ blue water. 3. Calculate for each country its equal share or ‘right’, which is the right over and above the reserved blue water. For the most upstream country this right simply equals the total nonreserved blue water resources generated in the entire basin divided by the total number of riparian countries. 4. Compare the calculated right of the most upstream country with the non-reserved blue water generated in that country. Any excess water has to be passed on to the downstream neighbouring country. 5. Steps 3 and 4 are now repeated for the second riparian country. Its right is calculated by adding the blue water received from the upstream country to the non-reserved blue water generated in all riparian countries except the most upstream, and dividing this by the number of remaining riparian countries (all riparian countries minus those located upstream; in this case all countries minus one). The second riparian country surrenders any non-reserved blue water in excess of its own right to the next downstream riparian. This step is repeated for all riparians. The above calculation procedure can be represented by two mathematical equations (Eqs. (A.2) and (A.3) in Appendix A). This allocation scenario has been applied to the Orange river, which is shared between Lesotho (LES), South Africa (RSA) and Namibia (NAM). Botswana also occupies part of the Orange basin (121 Gm2), but there is no known contribution of this part of the basin to the blue water flow, and Botswana being an upstream riparian, it is unlikely that it may claim downstream surface waters. For this reason Botswana will not be further considered here. Table 1 gives basic data on population, basin area and rainfall. These data are approximations based on GardnerOutlaw and Engelman (1997), Leemans and Cramer (1991), the Hydro1k database (USGS, 2000), Conley (1996), Conley and Van Niekerk (2000), Heyns (1995) and Savenije and Van der Zaag (2000). Table 1 also gives the resulting water allocation pattern, assuming that one quarter of all surface water generated in a country will be reserved for that country and cannot become available to another riparian (Rb ¼ 0:25). Other values for the reserved fraction may of course be considered or negotiated. The blue water component was estimated with an estimated average annual interception (the part of the rainfall that is directly evaporated before it can become blue or green water) I ¼ 0:32 m/yr, and a net runoff coefficient C ¼ 0:30:
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Table 1 Orange river: approximate data and resulting water allocation for criterion 1; I ¼ 0:32 m/yr, C ¼ 0:30; Rb ¼ 0:25 Orange
i
Pop N (M)
Area A (Gm2)
Rain P (m/yr)
Blue Qb (Gm3/yr)
Right Qr (Gm3/yr)
Transfer Qt (Gm3/yr)
New blue Qb0 (Gm3/yr)
LES RSA NAM Sum
1 2 3
2.0 30.0 0.5 32.5
30 576 242 848
0.85 0.36 0.22
4.8 7.6 0.0 12.4
3.1 3.1 3.1
0.5 3.1 0.0
4.3 5.0 3.1 12.4
2.2. Surface water, equally shared in terms of catchment area Criterion 1 is insensitive to differences in surface area of the riparian countries in the basin. If this is taken into account, the criterion may be slightly modified: Criterion 2: All surface waters generated in an (international) river basin should be shared by the riparian countries in proportion to each country’s area in the basin. The right to blue (surface) water of each riparian is now calculated by multiplying the available non-reserved blue water by the area that a riparian country occupies in the basin, and dividing it by the remaining basin area (i.e. excluding the area occupied by upstream countries). This calculation procedure is mathematically represented by Eq. (A.4). Any non-reserved blue water in excess of a country’s right is transferred downstream in exactly the same way as in the previous scenario (Eq. (A.3)).
2.3. Surface water; equally shared in per capita (population) terms If water is considered a right of every citizen, the criterion can be based on population size: Criterion 3: All surface waters generated in an (international) river basin should be shared by the riparian countries in proportion to the population. The right to blue (surface) water of each riparian is here calculated by multiplying the available non-reserved blue water by the population of a riparian country living in the basin, and dividing it by the remaining population (i.e. excluding the basin population living in upstream countries). This calculation procedure is mathematically represented by Eq. (A.5). Any non-reserved blue water in excess of a country’s right is transferred downstream in exactly the same way as in the previous scenario (Eq. (A.3)). Table 2 compares the water allocation that results from the three criteria defined so far (equal rights as to country, basin area and population). Since every human being has a basic right to access to water (Gleick, 1999), it could be argued that the population-based criterion (3) is better than the other two, which merely refer to administrative realities. However, none of the three criteria considers the fact that Namibia is an arid country, and that it depends more on surface water than humid Lesotho. The next section takes up this point, by including the green water component.
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Table 2 Orange river: resulting water allocation for three allocation criteria; Rb ¼ 0:25 Orange
LES RSA NAM Sum
Blue water generated Qb (Gm3/yr)
4.8 7.6 0.0 12.4
Blue water allocated Country Qb0 (Gm3/yr)
Area Qb0 (Gm3/yr)
Population Qb0 (Gm3/yr)
4.3 5.0 3.1 12.4
1.5 8.2 2.7 12.4
1.8 10.5 0.1 12.4
2.4. Blue and green water If all water resources are considered, including the green water used for the production of rainfed crops, then three new criteria can be formulated: Criterion 4: All blue and green water generated in an (international) river basin should be shared by the riparian countries equally (as far as possible). Criterion 5: All blue and green water generated in an (international) river basin should be shared by the riparian countries in proportion to each country’s area in the basin. Criterion 6: All blue and green water generated in an (international) river basin should be shared by the riparian countries in proportion to the population. These criteria consider green and blue water resources together. Since the values attached to green and blue water resources are not necessarily the same, it is important that agreement is reached on the weight of green water Wg relative to blue water. In the following we have simply assumed Wg ¼ 0:5; i.e. one unit of green water is equivalent to half a unit of blue water. But any other relative value of green to blue water may be considered or negotiated. For each country in the basin these new criteria would: 1. Assess the total water resources (blue and green water) generated. The green water component is estimated with Eq. (A.6), following the approach suggested by Savenije (1997). 2. Calculate its equal share or ‘right’, starting with the upper most riparian. The calculation procedure is similar to those used in the previous scenarios. 3. Calculate the amount of water in excess of the country’s right. 4. Calculate the total amount of negotiable blue (surface) water available to that country. 5. Since green water cannot be transferred, the amount to be transferred downstream is either the result of step 3 or step 4, whichever is smallest. Criterion 6 can be described mathematically by Eqs. (A.7) and (A.8). It can be seen that these equations are more general expressions for Eqs. (A.5) and (A.3). Eq. (A.5) is a specific case of the more general Eq. (A.7), and Eq. (A.3) is a specific case of Eq. (A.8), namely for Wg ¼ 0: Table 3 gives estimates of the green water and other components in the Orange river, as well as the result of applying criterion 6. Table 4 provides data on per capita water availability.
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Table 3 Orange river: approximate data including ‘green water’, and resulting water allocation for criterion 6; I ¼ 0:32 m/yr, C ¼ 0:30; Rb ¼ 0:25; Wg ¼ 0:5 Orange
i
Pop N (M)
Area A (Gm2)
Rain P (m/yr)
Green Qg (Gm3/yr)
Blue Qb (Gm3/yr)
Right Qr (Gm3/yr)
Transfer Qt (Gm3/yr)
New blue Qb0 (Gm3/yr)
LES RSA NAM Sum
1 2 3
2.0 30.0 0.5 32.5
30 576 242 848
0.85 0.36 0.22
11.2 17.7 0.0 28.9
4.8 7.6 0.0 12.4
1.5 17.9 0.3
3.6 0.3 0.0
1.2 10.9 0.3 12.4
Table 4 Orange river: per capita water availability for criterion 6; Rb ¼ 0:25; Wg ¼ 0:5 Orange
Per capita green water Qg (m3/cap/yr)
Per capita internally generated blue water Qb (m3/cap/yr)
Per capita new blue water Qb0 (m3/cap/yr)
LES RSA NAM Basin
5,580 591 0 889
2,391 253 0 381
598 363 595 381
Table 5 Orange river: comparing water allocation for the 6 criteria defined; Rb ¼ 0:25 Orange
Blue water generated Qb (Gm3/yr)
Blue water allocated for different allocation criteria (Gm3/yr) ‘Blue’ (Wg ¼ 0)
LES RSA NAM Sum
4.8 7.6 0.0 12.4
‘Green and blue’ (Wg ¼ 0:5)
Country
Area
Population Country
Area
Population
4.3 5.0 3.1 12.4
1.5 8.2 2.7 12.4
1.8 10.5 0.1 12.4
1.2 5.8 5.4 12.4
1.2 10.9 0.3 12.4
3.5 1.9 7.0 12.4
2.5. Results Table 5 compares the results of the criteria that only consider blue water with those that also take account of green water. One can observe that the latter criterion better caters for the needs of the dry downstream riparian population. The population-based criterion that takes blue and green water into account appears to result into the most equitable allocation of international waters. This is shown in Table 6, which gives the per capita blue water availability resulting from
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Table 6 Orange river: per capita New Blue water availability for the 6 criteria defined; Rb ¼ 0:25 Orange
Per capita New Blue water (m3/cap/yr) ‘Blue’ (Wg ¼ 0)
LES RSA NAM Basin
‘Green and blue’ (Wg ¼ 0:5)
Country
Area
Population
Country
Area
Population
2,146 167 6,191 381
763 273 5,304 381
884 349 286 381
1,764 63 13,911 381
598 194 10,752 381
598 363 595 381
criterion 6. Since this conclusion may not be valid for other cases, the population-based criteria for ‘blue’ and the ‘green and blue’ scenarios are also applied to the Nile and Incomati rivers.
3. Application of the criteria to other river basins 3.1. The Nile river The Nile basin is simplified by dividing the basin into three parts: the upper riparians (UPP), Sudan (SUD) and Egypt (EGY). Table 7 gives approximate data on population, basin area, rainfall and green and blue water generated (Gardner-Outlaw & Engelman, 1997; Leemans & Cramer, 1991; USGS, 2000; and modified from Conway, Krol, Alcamo, & Hulme, 1996). For the annual interception we use I ¼ 0:60 m/yr and C ¼ 0:15 as an estimate for the net runoff coefficient. Total blue water use in Sudan and Egypt amounts to some 74 Gm3/yr (Whittington, Waterbury, & McClelland, 1994), which is close to the average total yield of the basin. According to a 1959 treaty, Sudan may use 18.5 Gm3/yr, and Egypt 55.5 Gm3/yr. The upper riparian countries use negligible amounts of surface water. The population-based criteria are considered for the ‘blue’ and the ‘green and blue’ scenarios (criteria 3 and 6), with Wg ¼ 0:5: In fact, only when Wg drops below 0.09 will it affect the green and blue water allocation. This is due to the large volume of green water relative to blue water produced in the upper riparian countries (which is occasioned by the low runoff coefficient). In the first simulation the fraction of reserved surface water Rb ¼ 0: Table 7 also gives the resulting water allocation. Comparison of existing water use in the Nile basin with Table 7 shows that apparently the current arrangement partly takes green water into account, at least for the case of Egypt. Not taking green water into account would have left Egypt with 50% less surface water than it currently uses. It is also apparent that currently the generators of surface water (the upper riparians such as Ethiopia and Uganda) hardly use any. This latter issue has become increasingly unacceptable for some upper riparian countries (e.g. Ethiopia). It may therefore be more realistic to ‘reserve’ a certain fraction of generated surface water for the countries where it was generated. Table 8 shows the water sharing arrangements for various fractions Rb ; adopting the population criterion for the ‘green and blue’ scenario.
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‘Blue’ (Wg ¼ 0) population based
Nile
UPP SUD EGY Sum
‘Green and blue’ (Wg ¼ 0:5) population based
Pop N (M)
Area A Rain P Green Qg (Gm2) (M/yr) (Gm3/yr)
Blue Qb (Gm3/yr)
Right Qr (Gm3/yr)
Transfer Qt New blue Qb0 Right Qr (Gm3/yr) (Gm3/yr) (Gm3/yr)
Transfer Qt (Gm3/yr)
New blue Qb0 (Gm3/yr)
40 20 60 120
850 1,920 280 3,050
80.5 0.0 0.0 80.5
26.8 13.4 40.2
53.6 40.2 0.0
80.5 60.3 0.0
0.0 20.1 60.3 80.5
1.23 0.55 0.06
455.9 0.0 0.0 455.9
26.8 13.4 40.2 80.5
178.8 20.1 60.3
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Table 7 Nile river: Approximate data and resulting water allocation, population-based criteria; I ¼ 0:60 m/yr, C ¼ 0:15; Rb ¼ 0
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Table 8 Nile river: water allocation for different values of Rb ; for criterion 6; Wg ¼ 0:5 Nile
UPP SUD EGY Sum
Resulting blue water (m3/yr) for different values of Rb Rb ¼ 0:00
Rb ¼ 0:05
Rb ¼ 0:10
Rb ¼ 0:15
Rb ¼ 0:20
Rb ¼ 0:25
Rb ¼ 0:30
0.0 20.1 60.3 80.5
4.0 19.1 57.3 80.5
8.0 18.1 54.3 80.5
12.1 17.1 51.3 80.5
16.1 16.1 48.3 80.5
20.1 15.1 45.3 80.5
24.1 14.1 42.2 80.5
Table 9 Nile river: per capita water availability for criterion 6; Rb ¼ 0:25; Wg ¼ 0:5 Nile
UPP SUD EGY Basin
Per capita water resources (Gm3/cap/yr) Green water Qg
Blue water generated Qb
New blue water Qb0
11,397 0 0 3,799
2,011 0 0 670
503 754 754 670
It is suggested that negotiations between the riparian countries of the Nile could focus on establishing a fair value of Rb : This may help to de-politicise negotiations (Caponera, 1996; Bulloch & Darwish, 1993). In case the resulting water allocation affects certain riparians, negotiations could turn to, for instance, the possibilities of those countries ‘leasing’ blue waters ‘owned’ by other riparians. Table 9 gives the per capita water availability for criterion 6, if the fraction of reserved blue water is set at Rb ¼ 0:25: 3.2. The Incomati river The Incomati river is shared by South Africa (RSA), Swaziland (SWA) and Mozambique (MOZ). Table 10 gives basic data for the river (Gardner-Outlaw & Engelman, 1997; Leemans & Cramer, 1991; USGS, 2000; Carmo Vaz & Lopes Pereira, 2000), using the average annual interception I ¼ 0:40 m/yr and the net runoff coefficient C ¼ 0:30: Considering only the population-based criteria for both the ‘blue’ and the ‘green and blue’ scenarios, assuming Wg ¼ 0:5 and Rb ¼ 0:25; the water allocation would be as in Table 10, and the per capita water availability as in Table 11. A nearly identical sharing arrangement would be found for Rb ¼ 0: This is due to the fairly even rainfall distribution and generation of blue water across the Incomati basin. The ‘blue’ criterion suggests that South Africa can take 97% (2.54/2.61) of the blue Incomati water generated within its borders, as it has to surrender only 3%. Swaziland can use all blue water generated within its
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‘Blue’ (Wg ¼ 0) population based
Incomati
RSA SWA MOZ
‘Green and blue’ (Wg ¼ 0:5) population based
Pop N (M)
Area A (Gm2)
Rain P (M/yr)
Green Qg Blue Qb (Gm3/yr) (Gm3/yr)
Right Qr (Gm3/yr)
Transfer Qt (Gm3/yr)
New blue Qb0 Right Qr Transfer Qt (Gm3/yr) (Gm3/yr) (Gm3/yr)
New blue Qb0 (Gm3/yr)
4.0 0.6 2.0 6.6
28.5 3.0 14.7 46.2
0.71 0.79 0.67
6.08 0.83 2.77 9.68
1.89 0.28 0.94
0.07 0.05 0.00
2.54 0.37 1.24 4.15
2.43 0.40 1.32 4.15
2.61 0.35 1.19 4.15
4.82 0.72 2.41
0.18 0.13 0.00
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Table 10 Incomati river: approximate data and resulting water allocation, population based criteria, I ¼ 0:40 m/yr, C ¼ 0:30; Rb ¼ 0:25
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Table 11 Incomati river: per capita New Blue water availability for criteria 3 and 6; Rb ¼ 0:25; Wg ¼ 0:5 Incomati
RSA SWA MOZ Basin
Per capita New Blue water (m3/cap/yr) Population based, ‘Blue’
Population based, ‘Green and blue’
635 619 620 629
607 664 661 629
territory plus a quarter of the water released by South Africa. The major beneficiary of the water released by South Africa should be Mozambique. In fact, since the early 1970s and up until 1999 South Africa used up almost all the Incomati waters within its territory. During the dry season the riverbed at Komatipoort (where the Incomati flows from South Africa into Mozambique) used to be dry. This was considered unfair by Mozambique and in contravention of an earlier bilateral agreement between both countries. In 1999 South Africa, for the first time in 20 years, purposely surrendered water to Mozambique (some 1 m3/s during the dry season). The ‘green and blue’ scenario therefore seems to simulate the preferred situation better, suggesting that South Africa surrenders 7% of its blue water to the benefit of mainly Mozambique, increasing the blue water available to Mozambique with some 11% (1.32 Gm3/yr as against 1.19 Gm3/yr). If the value of green water had been equated to that of blue water (Wg ¼ 1), then South Africa would have surrendered 11% of Incomati water, and Mozambique would have had its blue water increased with 18% to 1.40 Gm3/yr. So in the Incomati, negotiations about water sharing could focus on the relative values of green and blue water resources.
4. Further refinements Two further refinements to the approach are proposed here. The first is to define an allocation key for real time operation. The second is to consider that only part of the water that is reserved for one country is actually consumed (e.g. for basic human requirements), whereas the remaining water (used e.g. for environmental requirements) flows into the next downstream riparian. 4.1. Proportional blue water right The above derivations are based on average flows, whereas in real time, the river flow fluctuates. For operational purposes there is a need to express the resulting water allocation for each country as a proportion or percentage of total blue water resources of that country (both internally generated and received from upstream countries). This proportional blue water right would then fix the water allocation for any flow regime. This is especially meaningful in times when less water is available than the average discharge.
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4.2. Consider partial consumption of the reserve It should be observed that in all the above examples, we have assumed that all reserved water would be consumed in the respective countries. In practice, this may often not be the case, and non-consumed reserved water may flow into the next downstream country. If we would take this into account, a more realistic picture of water flows would emerge. Here, we assume that reserved water may not be used by any other country, i.e. a downstream country would not be allowed to add the non-consumed reserved water of an upstream country to its water resources. We define Fc as the fraction of the reserved water that is consumed. A country would pass downstream the balance (the non-consumed portion) of its reserved blue water. In all the examples given so far it was assumed that Fc ¼ 1: Considering the Incomati river and assuming Fc ¼ 0:75; the estuary would receive a flow of 0.26 Gm3/yr ((1–0.75) 0.25 4.15) and the transfer flows between the riparian countries would be much higher than those given in Table 10, indicating that more water would remain in the river bed than suggested by the earlier examples.
5. Conclusion The criteria and algorithms developed in this paper attempt to operationalise the concept of ‘equity’, which is considered the key allocation principle for the sharing of international water resources. Applying these criteria to the Orange, Nile and Incomati rivers indicate that the criterion that considers all (blue and green) water resources and that uses the basin population as the main allocation variable yields a water allocation pattern that may be considered the most equitable. For operational purposes, the allocation is best defined in proportional terms, so that the allocation is known for varying amounts of water generation. An important aspect of considering the green and blue water resources jointly is to reach agreement over the value of green water relative to blue water. Moreover, the Nile example shows that the fraction of reserved water, which is defined as the basic entitlement of each riparian country, is a crucial variable over which the riparian countries should reach consensus. After the basic entitlement of each country has been established, any additional water transfers can be negotiated bilaterally. The above conclusions should be considered preliminary, as the data used for the three rivers are approximations. Moreover, the figures used to quantify the water resources are average values. Data on median flows would be more meaningful. For scenario planning, data on low flows that occur, say, in 1 out of 5 years, would also be very relevant. Although the algorithms may seem complicated to a person not familiar with mathematical formulation, they are in fact very simple. This is both a weakness and a strength. One weakness is that the variability in water availability within countries, both in time and space, is not taken into account. The strength of the method is that the algorithms are transparent, without ‘double counting’ of water resources between riparian countries, and that they may be easily understood by politicians and decision-makers. This will ensure that the method is trusted and not seen as a ‘black box’ only to be understood (and manipulated) by experts. The suggestions made are exploratory and conceptual. They are meant to stimulate critical thinking about the problem of sharing the waters in a river basin. The approach as developed here should not be considered a
P. van der Zaag et al. / Water Policy 4 (2002) 19–32
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recipe that calculates the ‘right’ water allocations. It is a tool that may assist in opening up new options and perspectives when negotiations are tedious. Acknowledgements The authors have benefited from comments by an anonymous reviewer, which is gratefully acknowledged. An earlier version of this paper was presented at the Fourth Biennial Congress of the African Division of the International Association of Hydraulic Research held in Windhoek, Namibia, 7–9 June 2000. Appendix A Equations Qb ¼ C A max½P I; 0; Qr;i ¼
Qt;i1 þ ð1 Rb Þ
ðA:1Þ n X
! Qb
i
1 niþ1
Qt;i ¼ Qt;i1 þ ð1 Rb ÞQb;i Qr;i ! n X Ai Qr;i ¼ Qt;i1 þ ð1 Rb Þ Qb Pn i
i
Qr;i ¼
Qt;i1 þ ð1 Rb Þ
n X i
! Qb
ðA:2Þ ðA:3Þ ðA:4Þ
A
N Pn i i N
ðA:5Þ
Qg ¼ ð1 CÞA max½P I; 0 Qr;i ¼
Qt;i1 þ Wg
n X
Qg þ ð1 Rb Þ
i
ðA:6Þ n X i
! Qb
N Pn i i N
ðA:7Þ
Qt;i ¼ minIQt;i1 þ Wg Qg;i þ ð1 Rb ÞQb;i Qr;i ; Qt;i1 þ ð1 Rb ÞQb;i m;
ðA:8Þ
where: Ai =basin area occupied by country i (Gm2) C=net runoff coefficient (F) Fc =fraction of the reserved blue water that is consumed I=average annual interception (m/yr) i=prefix for the riparian countries involved, with i ¼ 1 for the upper most basin country, and i ¼ n for the most downstream n=total number of basin countries
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Ni =the population living in that part of the river basin occupied by country i P=average annual precipitation (m/yr) Qb;i =blue water generated in country i (Gm3/yr) Qg;i =green water generated in country i (Gm3/yr) Qr;i =right to blue water of country i over and above the reserved blue water (Gm3/yr) Qt;i =surplus blue water to be transferred to downstream countries (Gm3/yr) Rb =fraction of blue water reserved for each riparian country Wg =weight of green water relative to blue water References Bulloch, J., & Darwish, A. (1993). Water wars; coming conflicts in the Middle East. London: Victor Gollancz. Caponera, D. A. (1996). Conflicts over international river basins in Africa, the Middle East and Asia. Reciel, 5(2), 97–106. ! & Lopes Pereira, A. (2000). The Incomati and Limpopo international river basins; a view from Carmo Vaz, A., downstream. Water Policy, 2(1–2), 99–112. Conley, A. H. (1996). A synoptic view of water resources in Southern Africa. Unpublished paper. Conley, A. H., & van Niekerk, P. H. (2000). Sustainable management of international waters: The Orange case. Water Policy, 2(1–2), 131–149. Conway, D., Krol, M., Alcamo, J., & Hulme, M. (1996). Future availability of water in Egypt: The interaction of global, regional and basin scale driving forces in the Nile basin. Ambio, 25(5), 336–342. Falkenmark, M. (1995). Coping with water scarcity under rapid population growth. Paper presented at the Conference of SADC water ministers, Pretoria, 23–24 November. Gardner-Outlaw, T., & Engelman, R. (1997). Sustaining water, easing scarcity; a second update. Washington DC: Population Action International. Gleick, P. (1999). The human right to water. Water Policy, 1(5), 487–503. Heyns, P. (1995). Existing and planned water development projects on international rivers within the SADC region. Paper presented at the Conference of SADC water ministers, Pretoria, 23–24 November. Leemans, R., & Cramer, W. P. (1991). The IIASA database for mean monthly values of temperature, precipitation and cloudiness on a global terrestrial grid. Laxenburg: International Institute for Applied Systems Analysis. McCaffrey, S. C. (1993). Water, politics and international law. In P. H. Gleick (Ed.), Water in crisis; guide to the world’s water resources. Oxford: Oxford University Press. McCaffrey, S. C. (1998). The UN Convention on the Law of the Non-Navigational Uses of International Watercourses: prospects and pitfalls. In: S. M. A. Salman & L. Boisson de Chazournes (Eds.), International watercourses, enhancing cooperation and managing conflict. World Bank Technical Paper No. 414. Washington DC: The World Bank. Postel, S. (1992). Last oasis, facing water scarcity. New York: W.W. Norton. Savenije, H. H. G. (1997). Determination of evaporation from a catchment water balance at a monthly time scale. Hydrology and Earth System Sciences, 1(1), 93–100. Savenije, H. H. G., & van der Zaag, P. (2000). Conceptual framework for the management of shared river basins, with special reference to SADC and EU. Water Policy, 2(1–2), 9–45. Seyam, I. M. (1999). Algorithms for water resources distribution in international river basins. M.Sc. Thesis. IHE, Delft. USGS (2000). Hydro1k elevation derivative database. EROS Data Centre, US Geological Survey. http://edc.usgs.gov/ landdaac/gtopo30/hydro/ Whittington, D., Waterbury, J., & McClelland, E. (1994). Towards a new Nile waters agreement among riparians. Ethioscope, 1, 11–17. Wolf, A. T. (1999). Criteria for equitable allocations: The heart of international water conflict. Natural Resources Forum, 23(1), 3–30. Wouters, P. (1997). Present status of international water law. In: P. Wouters (Ed.), International water law; selected writings of Prof. Charles B. Bourne. London: Kluwer Law International.
Towards measurable criteria for the equitable sharing of international water resources Pieter van der Zaag*, I.M. Seyam, Hubert H.G. Savenije IHE Delft, P.O. Box 3015, 2601 DA Delft, The Netherlands Received 18 February 2001; received in revised form 11 September 2001; accepted 16 December 2001
Abstract Equity is key to the allocation of international water resources. Six possible criteria and allocation algorithms that operationalise the equity concept, are developed and applied to the Orange, Nile and Incomati rivers. The criterion that considers all (blue and green) water resources and that uses the basin population as the main allocation variable yields the most equitable water allocation. Two important variables are identified over which the riparian countries should reach consensus:
1. The value of green water relative to blue water. 2. The fraction of reserved water, which is defined as the basic entitlement of each riparian country. These findings are based on approximate data and have therefore a limited validity. With this caveat it is suggested that the approach developed in this article may help de-politicise negotiations between riparian countries and provide fresh perspectives that may unlock stalemates during negotiations. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Allocation algorithms; Equity; Green water; Incomati river; International water resources; Nile river; Orange river; Water allocation; Water law
1. Introduction The United Nations Convention on the Law of the Non-Navigational Uses of International Watercourses, adopted by the General Assembly in 1997, provides a framework for negotiations between countries sharing an international water resource. The convention defines the obligation *Corresponding author. IHE Delft, PO Box MP 600, Mount Pleasant, Harare, Zimbabwe. Tel.: +263-4-336-725; fax: +263-4-336-740. E-mail address: [email protected] (P. van der Zaag). 1366-7017/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 1 3 6 6 - 7 0 1 7 ( 0 2 ) 0 0 0 0 3 - X
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not to cause appreciable harm and the right to reasonable and equitable use as co-equal criteria for the allocation of water between riparian countries (McCaffrey, 1998, Chap. 2). These principles have to be translated into concrete agreements through negotiations between the countries involved. Some authors have argued that the principle of equity is key to water allocation (Wouters, 1997; Wolf, 1999), which was also the premise of the 1966 Helsinki Rules (McCaffrey, 1993, Chap. 8). The principle of reasonable and equitable use (Article 5 of the UN Convention), however, is defined in general terms, and is thus prone to subjective interpretation. Postel (1992, p. 189) has argued that clearer criteria are needed. This paper attempts to define measurable criteria on the basis of which water resources can be allocated to the riparian countries in an equitable manner. Such measurable criteria may facilitate negotiations between riparians that are in conflict over the issue (Seyam, 1999). In fact, jointly defining such criteria could be a central activity during negotiations. The paper does not take into account criteria other than that of equity. Once equitable water allocations have been agreed upon, riparian countries may jointly decide to transfer water from one to another, for instance against compensation (in the spirit of Article 7 of the UN Convention). Since you can only sell something that belongs to you, the rights of the riparian countries sharing a common water resource have to be established before economic or financial transactions concerning water allocation can occur. Deciding to let market forces play a role in the (re)allocation of water resources or not should therefore be a secondary issue. The paper consists of three parts. The first part defines six possible criteria and algorithms for the equitable allocation of water resources, using the Orange river (known as Senqu river in Lesotho) as an example. The criteria take into account, on the demand side, the number of countries sharing the water, the basin areas of each riparian country, and the riparian population. On the supply side, the criteria consider ‘blue’ water and ‘green’ water (Falkenmark, 1995). Blue water is renewable water that occurs in rivers and aquifers. Green water is renewable water that occurs in the soil; it is the part of the rainfall that infiltrates into the root zone and is directly used by plants for biomass production through transpiration. Green water is a very important resource for agricultural production, which is generally overlooked in water resources assessment. The second part of the paper applies some of the criteria to the Nile and Incomati (or Komati) rivers. The third part of the paper provides some ideas for refining the approach. The suggestions made in this paper are exploratory and conceptual. They are meant to stimulate critical thinking about the problem of sharing the waters in an international river basin.
2. Possible criteria for the equitable sharing of international water resources 2.1. Surface water, equally shared among countries The simplest and most straightforward criterion for the equitable sharing of international waters may be formulated as: Criterion 1: All surface waters generated in an (international) river basin should be shared by the riparian countries equally (as far as possible).
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To operationalise this criterion it should be accepted that it is not possible to pump water from down- to upstream countries (hence the addition: as far as possible). That is the reason why the proposed procedure is not just to split the available water equally. The procedure moves from upstream to downstream whereby at each border crossing the remaining water is shared equally among the downstream countries. It is further assumed that a certain fraction Rb of the surface water generated in each riparian is ‘reserved’ for that country, and remains outside the negotiations. This ‘reserve’ may be used for primary water requirements of the basin population and for the water requirements of riverine ecosystems. To further operationalise criterion 1, the following steps are proposed: 1. Assess for each of the basin countries the amount of blue water generated in that country. In this paper, we estimate the blue water component using Eq. (A.1) (Appendix A), as proposed by Savenije (1997). 2. Subtract the ‘reserved’ blue water. 3. Calculate for each country its equal share or ‘right’, which is the right over and above the reserved blue water. For the most upstream country this right simply equals the total nonreserved blue water resources generated in the entire basin divided by the total number of riparian countries. 4. Compare the calculated right of the most upstream country with the non-reserved blue water generated in that country. Any excess water has to be passed on to the downstream neighbouring country. 5. Steps 3 and 4 are now repeated for the second riparian country. Its right is calculated by adding the blue water received from the upstream country to the non-reserved blue water generated in all riparian countries except the most upstream, and dividing this by the number of remaining riparian countries (all riparian countries minus those located upstream; in this case all countries minus one). The second riparian country surrenders any non-reserved blue water in excess of its own right to the next downstream riparian. This step is repeated for all riparians. The above calculation procedure can be represented by two mathematical equations (Eqs. (A.2) and (A.3) in Appendix A). This allocation scenario has been applied to the Orange river, which is shared between Lesotho (LES), South Africa (RSA) and Namibia (NAM). Botswana also occupies part of the Orange basin (121 Gm2), but there is no known contribution of this part of the basin to the blue water flow, and Botswana being an upstream riparian, it is unlikely that it may claim downstream surface waters. For this reason Botswana will not be further considered here. Table 1 gives basic data on population, basin area and rainfall. These data are approximations based on GardnerOutlaw and Engelman (1997), Leemans and Cramer (1991), the Hydro1k database (USGS, 2000), Conley (1996), Conley and Van Niekerk (2000), Heyns (1995) and Savenije and Van der Zaag (2000). Table 1 also gives the resulting water allocation pattern, assuming that one quarter of all surface water generated in a country will be reserved for that country and cannot become available to another riparian (Rb ¼ 0:25). Other values for the reserved fraction may of course be considered or negotiated. The blue water component was estimated with an estimated average annual interception (the part of the rainfall that is directly evaporated before it can become blue or green water) I ¼ 0:32 m/yr, and a net runoff coefficient C ¼ 0:30:
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Table 1 Orange river: approximate data and resulting water allocation for criterion 1; I ¼ 0:32 m/yr, C ¼ 0:30; Rb ¼ 0:25 Orange
i
Pop N (M)
Area A (Gm2)
Rain P (m/yr)
Blue Qb (Gm3/yr)
Right Qr (Gm3/yr)
Transfer Qt (Gm3/yr)
New blue Qb0 (Gm3/yr)
LES RSA NAM Sum
1 2 3
2.0 30.0 0.5 32.5
30 576 242 848
0.85 0.36 0.22
4.8 7.6 0.0 12.4
3.1 3.1 3.1
0.5 3.1 0.0
4.3 5.0 3.1 12.4
2.2. Surface water, equally shared in terms of catchment area Criterion 1 is insensitive to differences in surface area of the riparian countries in the basin. If this is taken into account, the criterion may be slightly modified: Criterion 2: All surface waters generated in an (international) river basin should be shared by the riparian countries in proportion to each country’s area in the basin. The right to blue (surface) water of each riparian is now calculated by multiplying the available non-reserved blue water by the area that a riparian country occupies in the basin, and dividing it by the remaining basin area (i.e. excluding the area occupied by upstream countries). This calculation procedure is mathematically represented by Eq. (A.4). Any non-reserved blue water in excess of a country’s right is transferred downstream in exactly the same way as in the previous scenario (Eq. (A.3)).
2.3. Surface water; equally shared in per capita (population) terms If water is considered a right of every citizen, the criterion can be based on population size: Criterion 3: All surface waters generated in an (international) river basin should be shared by the riparian countries in proportion to the population. The right to blue (surface) water of each riparian is here calculated by multiplying the available non-reserved blue water by the population of a riparian country living in the basin, and dividing it by the remaining population (i.e. excluding the basin population living in upstream countries). This calculation procedure is mathematically represented by Eq. (A.5). Any non-reserved blue water in excess of a country’s right is transferred downstream in exactly the same way as in the previous scenario (Eq. (A.3)). Table 2 compares the water allocation that results from the three criteria defined so far (equal rights as to country, basin area and population). Since every human being has a basic right to access to water (Gleick, 1999), it could be argued that the population-based criterion (3) is better than the other two, which merely refer to administrative realities. However, none of the three criteria considers the fact that Namibia is an arid country, and that it depends more on surface water than humid Lesotho. The next section takes up this point, by including the green water component.
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Table 2 Orange river: resulting water allocation for three allocation criteria; Rb ¼ 0:25 Orange
LES RSA NAM Sum
Blue water generated Qb (Gm3/yr)
4.8 7.6 0.0 12.4
Blue water allocated Country Qb0 (Gm3/yr)
Area Qb0 (Gm3/yr)
Population Qb0 (Gm3/yr)
4.3 5.0 3.1 12.4
1.5 8.2 2.7 12.4
1.8 10.5 0.1 12.4
2.4. Blue and green water If all water resources are considered, including the green water used for the production of rainfed crops, then three new criteria can be formulated: Criterion 4: All blue and green water generated in an (international) river basin should be shared by the riparian countries equally (as far as possible). Criterion 5: All blue and green water generated in an (international) river basin should be shared by the riparian countries in proportion to each country’s area in the basin. Criterion 6: All blue and green water generated in an (international) river basin should be shared by the riparian countries in proportion to the population. These criteria consider green and blue water resources together. Since the values attached to green and blue water resources are not necessarily the same, it is important that agreement is reached on the weight of green water Wg relative to blue water. In the following we have simply assumed Wg ¼ 0:5; i.e. one unit of green water is equivalent to half a unit of blue water. But any other relative value of green to blue water may be considered or negotiated. For each country in the basin these new criteria would: 1. Assess the total water resources (blue and green water) generated. The green water component is estimated with Eq. (A.6), following the approach suggested by Savenije (1997). 2. Calculate its equal share or ‘right’, starting with the upper most riparian. The calculation procedure is similar to those used in the previous scenarios. 3. Calculate the amount of water in excess of the country’s right. 4. Calculate the total amount of negotiable blue (surface) water available to that country. 5. Since green water cannot be transferred, the amount to be transferred downstream is either the result of step 3 or step 4, whichever is smallest. Criterion 6 can be described mathematically by Eqs. (A.7) and (A.8). It can be seen that these equations are more general expressions for Eqs. (A.5) and (A.3). Eq. (A.5) is a specific case of the more general Eq. (A.7), and Eq. (A.3) is a specific case of Eq. (A.8), namely for Wg ¼ 0: Table 3 gives estimates of the green water and other components in the Orange river, as well as the result of applying criterion 6. Table 4 provides data on per capita water availability.
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Table 3 Orange river: approximate data including ‘green water’, and resulting water allocation for criterion 6; I ¼ 0:32 m/yr, C ¼ 0:30; Rb ¼ 0:25; Wg ¼ 0:5 Orange
i
Pop N (M)
Area A (Gm2)
Rain P (m/yr)
Green Qg (Gm3/yr)
Blue Qb (Gm3/yr)
Right Qr (Gm3/yr)
Transfer Qt (Gm3/yr)
New blue Qb0 (Gm3/yr)
LES RSA NAM Sum
1 2 3
2.0 30.0 0.5 32.5
30 576 242 848
0.85 0.36 0.22
11.2 17.7 0.0 28.9
4.8 7.6 0.0 12.4
1.5 17.9 0.3
3.6 0.3 0.0
1.2 10.9 0.3 12.4
Table 4 Orange river: per capita water availability for criterion 6; Rb ¼ 0:25; Wg ¼ 0:5 Orange
Per capita green water Qg (m3/cap/yr)
Per capita internally generated blue water Qb (m3/cap/yr)
Per capita new blue water Qb0 (m3/cap/yr)
LES RSA NAM Basin
5,580 591 0 889
2,391 253 0 381
598 363 595 381
Table 5 Orange river: comparing water allocation for the 6 criteria defined; Rb ¼ 0:25 Orange
Blue water generated Qb (Gm3/yr)
Blue water allocated for different allocation criteria (Gm3/yr) ‘Blue’ (Wg ¼ 0)
LES RSA NAM Sum
4.8 7.6 0.0 12.4
‘Green and blue’ (Wg ¼ 0:5)
Country
Area
Population Country
Area
Population
4.3 5.0 3.1 12.4
1.5 8.2 2.7 12.4
1.8 10.5 0.1 12.4
1.2 5.8 5.4 12.4
1.2 10.9 0.3 12.4
3.5 1.9 7.0 12.4
2.5. Results Table 5 compares the results of the criteria that only consider blue water with those that also take account of green water. One can observe that the latter criterion better caters for the needs of the dry downstream riparian population. The population-based criterion that takes blue and green water into account appears to result into the most equitable allocation of international waters. This is shown in Table 6, which gives the per capita blue water availability resulting from
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Table 6 Orange river: per capita New Blue water availability for the 6 criteria defined; Rb ¼ 0:25 Orange
Per capita New Blue water (m3/cap/yr) ‘Blue’ (Wg ¼ 0)
LES RSA NAM Basin
‘Green and blue’ (Wg ¼ 0:5)
Country
Area
Population
Country
Area
Population
2,146 167 6,191 381
763 273 5,304 381
884 349 286 381
1,764 63 13,911 381
598 194 10,752 381
598 363 595 381
criterion 6. Since this conclusion may not be valid for other cases, the population-based criteria for ‘blue’ and the ‘green and blue’ scenarios are also applied to the Nile and Incomati rivers.
3. Application of the criteria to other river basins 3.1. The Nile river The Nile basin is simplified by dividing the basin into three parts: the upper riparians (UPP), Sudan (SUD) and Egypt (EGY). Table 7 gives approximate data on population, basin area, rainfall and green and blue water generated (Gardner-Outlaw & Engelman, 1997; Leemans & Cramer, 1991; USGS, 2000; and modified from Conway, Krol, Alcamo, & Hulme, 1996). For the annual interception we use I ¼ 0:60 m/yr and C ¼ 0:15 as an estimate for the net runoff coefficient. Total blue water use in Sudan and Egypt amounts to some 74 Gm3/yr (Whittington, Waterbury, & McClelland, 1994), which is close to the average total yield of the basin. According to a 1959 treaty, Sudan may use 18.5 Gm3/yr, and Egypt 55.5 Gm3/yr. The upper riparian countries use negligible amounts of surface water. The population-based criteria are considered for the ‘blue’ and the ‘green and blue’ scenarios (criteria 3 and 6), with Wg ¼ 0:5: In fact, only when Wg drops below 0.09 will it affect the green and blue water allocation. This is due to the large volume of green water relative to blue water produced in the upper riparian countries (which is occasioned by the low runoff coefficient). In the first simulation the fraction of reserved surface water Rb ¼ 0: Table 7 also gives the resulting water allocation. Comparison of existing water use in the Nile basin with Table 7 shows that apparently the current arrangement partly takes green water into account, at least for the case of Egypt. Not taking green water into account would have left Egypt with 50% less surface water than it currently uses. It is also apparent that currently the generators of surface water (the upper riparians such as Ethiopia and Uganda) hardly use any. This latter issue has become increasingly unacceptable for some upper riparian countries (e.g. Ethiopia). It may therefore be more realistic to ‘reserve’ a certain fraction of generated surface water for the countries where it was generated. Table 8 shows the water sharing arrangements for various fractions Rb ; adopting the population criterion for the ‘green and blue’ scenario.
26
‘Blue’ (Wg ¼ 0) population based
Nile
UPP SUD EGY Sum
‘Green and blue’ (Wg ¼ 0:5) population based
Pop N (M)
Area A Rain P Green Qg (Gm2) (M/yr) (Gm3/yr)
Blue Qb (Gm3/yr)
Right Qr (Gm3/yr)
Transfer Qt New blue Qb0 Right Qr (Gm3/yr) (Gm3/yr) (Gm3/yr)
Transfer Qt (Gm3/yr)
New blue Qb0 (Gm3/yr)
40 20 60 120
850 1,920 280 3,050
80.5 0.0 0.0 80.5
26.8 13.4 40.2
53.6 40.2 0.0
80.5 60.3 0.0
0.0 20.1 60.3 80.5
1.23 0.55 0.06
455.9 0.0 0.0 455.9
26.8 13.4 40.2 80.5
178.8 20.1 60.3
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Table 7 Nile river: Approximate data and resulting water allocation, population-based criteria; I ¼ 0:60 m/yr, C ¼ 0:15; Rb ¼ 0
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Table 8 Nile river: water allocation for different values of Rb ; for criterion 6; Wg ¼ 0:5 Nile
UPP SUD EGY Sum
Resulting blue water (m3/yr) for different values of Rb Rb ¼ 0:00
Rb ¼ 0:05
Rb ¼ 0:10
Rb ¼ 0:15
Rb ¼ 0:20
Rb ¼ 0:25
Rb ¼ 0:30
0.0 20.1 60.3 80.5
4.0 19.1 57.3 80.5
8.0 18.1 54.3 80.5
12.1 17.1 51.3 80.5
16.1 16.1 48.3 80.5
20.1 15.1 45.3 80.5
24.1 14.1 42.2 80.5
Table 9 Nile river: per capita water availability for criterion 6; Rb ¼ 0:25; Wg ¼ 0:5 Nile
UPP SUD EGY Basin
Per capita water resources (Gm3/cap/yr) Green water Qg
Blue water generated Qb
New blue water Qb0
11,397 0 0 3,799
2,011 0 0 670
503 754 754 670
It is suggested that negotiations between the riparian countries of the Nile could focus on establishing a fair value of Rb : This may help to de-politicise negotiations (Caponera, 1996; Bulloch & Darwish, 1993). In case the resulting water allocation affects certain riparians, negotiations could turn to, for instance, the possibilities of those countries ‘leasing’ blue waters ‘owned’ by other riparians. Table 9 gives the per capita water availability for criterion 6, if the fraction of reserved blue water is set at Rb ¼ 0:25: 3.2. The Incomati river The Incomati river is shared by South Africa (RSA), Swaziland (SWA) and Mozambique (MOZ). Table 10 gives basic data for the river (Gardner-Outlaw & Engelman, 1997; Leemans & Cramer, 1991; USGS, 2000; Carmo Vaz & Lopes Pereira, 2000), using the average annual interception I ¼ 0:40 m/yr and the net runoff coefficient C ¼ 0:30: Considering only the population-based criteria for both the ‘blue’ and the ‘green and blue’ scenarios, assuming Wg ¼ 0:5 and Rb ¼ 0:25; the water allocation would be as in Table 10, and the per capita water availability as in Table 11. A nearly identical sharing arrangement would be found for Rb ¼ 0: This is due to the fairly even rainfall distribution and generation of blue water across the Incomati basin. The ‘blue’ criterion suggests that South Africa can take 97% (2.54/2.61) of the blue Incomati water generated within its borders, as it has to surrender only 3%. Swaziland can use all blue water generated within its
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‘Blue’ (Wg ¼ 0) population based
Incomati
RSA SWA MOZ
‘Green and blue’ (Wg ¼ 0:5) population based
Pop N (M)
Area A (Gm2)
Rain P (M/yr)
Green Qg Blue Qb (Gm3/yr) (Gm3/yr)
Right Qr (Gm3/yr)
Transfer Qt (Gm3/yr)
New blue Qb0 Right Qr Transfer Qt (Gm3/yr) (Gm3/yr) (Gm3/yr)
New blue Qb0 (Gm3/yr)
4.0 0.6 2.0 6.6
28.5 3.0 14.7 46.2
0.71 0.79 0.67
6.08 0.83 2.77 9.68
1.89 0.28 0.94
0.07 0.05 0.00
2.54 0.37 1.24 4.15
2.43 0.40 1.32 4.15
2.61 0.35 1.19 4.15
4.82 0.72 2.41
0.18 0.13 0.00
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Table 10 Incomati river: approximate data and resulting water allocation, population based criteria, I ¼ 0:40 m/yr, C ¼ 0:30; Rb ¼ 0:25
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Table 11 Incomati river: per capita New Blue water availability for criteria 3 and 6; Rb ¼ 0:25; Wg ¼ 0:5 Incomati
RSA SWA MOZ Basin
Per capita New Blue water (m3/cap/yr) Population based, ‘Blue’
Population based, ‘Green and blue’
635 619 620 629
607 664 661 629
territory plus a quarter of the water released by South Africa. The major beneficiary of the water released by South Africa should be Mozambique. In fact, since the early 1970s and up until 1999 South Africa used up almost all the Incomati waters within its territory. During the dry season the riverbed at Komatipoort (where the Incomati flows from South Africa into Mozambique) used to be dry. This was considered unfair by Mozambique and in contravention of an earlier bilateral agreement between both countries. In 1999 South Africa, for the first time in 20 years, purposely surrendered water to Mozambique (some 1 m3/s during the dry season). The ‘green and blue’ scenario therefore seems to simulate the preferred situation better, suggesting that South Africa surrenders 7% of its blue water to the benefit of mainly Mozambique, increasing the blue water available to Mozambique with some 11% (1.32 Gm3/yr as against 1.19 Gm3/yr). If the value of green water had been equated to that of blue water (Wg ¼ 1), then South Africa would have surrendered 11% of Incomati water, and Mozambique would have had its blue water increased with 18% to 1.40 Gm3/yr. So in the Incomati, negotiations about water sharing could focus on the relative values of green and blue water resources.
4. Further refinements Two further refinements to the approach are proposed here. The first is to define an allocation key for real time operation. The second is to consider that only part of the water that is reserved for one country is actually consumed (e.g. for basic human requirements), whereas the remaining water (used e.g. for environmental requirements) flows into the next downstream riparian. 4.1. Proportional blue water right The above derivations are based on average flows, whereas in real time, the river flow fluctuates. For operational purposes there is a need to express the resulting water allocation for each country as a proportion or percentage of total blue water resources of that country (both internally generated and received from upstream countries). This proportional blue water right would then fix the water allocation for any flow regime. This is especially meaningful in times when less water is available than the average discharge.
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4.2. Consider partial consumption of the reserve It should be observed that in all the above examples, we have assumed that all reserved water would be consumed in the respective countries. In practice, this may often not be the case, and non-consumed reserved water may flow into the next downstream country. If we would take this into account, a more realistic picture of water flows would emerge. Here, we assume that reserved water may not be used by any other country, i.e. a downstream country would not be allowed to add the non-consumed reserved water of an upstream country to its water resources. We define Fc as the fraction of the reserved water that is consumed. A country would pass downstream the balance (the non-consumed portion) of its reserved blue water. In all the examples given so far it was assumed that Fc ¼ 1: Considering the Incomati river and assuming Fc ¼ 0:75; the estuary would receive a flow of 0.26 Gm3/yr ((1–0.75) 0.25 4.15) and the transfer flows between the riparian countries would be much higher than those given in Table 10, indicating that more water would remain in the river bed than suggested by the earlier examples.
5. Conclusion The criteria and algorithms developed in this paper attempt to operationalise the concept of ‘equity’, which is considered the key allocation principle for the sharing of international water resources. Applying these criteria to the Orange, Nile and Incomati rivers indicate that the criterion that considers all (blue and green) water resources and that uses the basin population as the main allocation variable yields a water allocation pattern that may be considered the most equitable. For operational purposes, the allocation is best defined in proportional terms, so that the allocation is known for varying amounts of water generation. An important aspect of considering the green and blue water resources jointly is to reach agreement over the value of green water relative to blue water. Moreover, the Nile example shows that the fraction of reserved water, which is defined as the basic entitlement of each riparian country, is a crucial variable over which the riparian countries should reach consensus. After the basic entitlement of each country has been established, any additional water transfers can be negotiated bilaterally. The above conclusions should be considered preliminary, as the data used for the three rivers are approximations. Moreover, the figures used to quantify the water resources are average values. Data on median flows would be more meaningful. For scenario planning, data on low flows that occur, say, in 1 out of 5 years, would also be very relevant. Although the algorithms may seem complicated to a person not familiar with mathematical formulation, they are in fact very simple. This is both a weakness and a strength. One weakness is that the variability in water availability within countries, both in time and space, is not taken into account. The strength of the method is that the algorithms are transparent, without ‘double counting’ of water resources between riparian countries, and that they may be easily understood by politicians and decision-makers. This will ensure that the method is trusted and not seen as a ‘black box’ only to be understood (and manipulated) by experts. The suggestions made are exploratory and conceptual. They are meant to stimulate critical thinking about the problem of sharing the waters in a river basin. The approach as developed here should not be considered a
P. van der Zaag et al. / Water Policy 4 (2002) 19–32
31
recipe that calculates the ‘right’ water allocations. It is a tool that may assist in opening up new options and perspectives when negotiations are tedious. Acknowledgements The authors have benefited from comments by an anonymous reviewer, which is gratefully acknowledged. An earlier version of this paper was presented at the Fourth Biennial Congress of the African Division of the International Association of Hydraulic Research held in Windhoek, Namibia, 7–9 June 2000. Appendix A Equations Qb ¼ C A max½P I; 0; Qr;i ¼
Qt;i1 þ ð1 Rb Þ
ðA:1Þ n X
! Qb
i
1 niþ1
Qt;i ¼ Qt;i1 þ ð1 Rb ÞQb;i Qr;i ! n X Ai Qr;i ¼ Qt;i1 þ ð1 Rb Þ Qb Pn i
i
Qr;i ¼
Qt;i1 þ ð1 Rb Þ
n X i
! Qb
ðA:2Þ ðA:3Þ ðA:4Þ
A
N Pn i i N
ðA:5Þ
Qg ¼ ð1 CÞA max½P I; 0 Qr;i ¼
Qt;i1 þ Wg
n X
Qg þ ð1 Rb Þ
i
ðA:6Þ n X i
! Qb
N Pn i i N
ðA:7Þ
Qt;i ¼ minIQt;i1 þ Wg Qg;i þ ð1 Rb ÞQb;i Qr;i ; Qt;i1 þ ð1 Rb ÞQb;i m;
ðA:8Þ
where: Ai =basin area occupied by country i (Gm2) C=net runoff coefficient (F) Fc =fraction of the reserved blue water that is consumed I=average annual interception (m/yr) i=prefix for the riparian countries involved, with i ¼ 1 for the upper most basin country, and i ¼ n for the most downstream n=total number of basin countries
32
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Ni =the population living in that part of the river basin occupied by country i P=average annual precipitation (m/yr) Qb;i =blue water generated in country i (Gm3/yr) Qg;i =green water generated in country i (Gm3/yr) Qr;i =right to blue water of country i over and above the reserved blue water (Gm3/yr) Qt;i =surplus blue water to be transferred to downstream countries (Gm3/yr) Rb =fraction of blue water reserved for each riparian country Wg =weight of green water relative to blue water References Bulloch, J., & Darwish, A. (1993). Water wars; coming conflicts in the Middle East. London: Victor Gollancz. Caponera, D. A. (1996). Conflicts over international river basins in Africa, the Middle East and Asia. Reciel, 5(2), 97–106. ! & Lopes Pereira, A. (2000). The Incomati and Limpopo international river basins; a view from Carmo Vaz, A., downstream. Water Policy, 2(1–2), 99–112. Conley, A. H. (1996). A synoptic view of water resources in Southern Africa. Unpublished paper. Conley, A. H., & van Niekerk, P. H. (2000). Sustainable management of international waters: The Orange case. Water Policy, 2(1–2), 131–149. Conway, D., Krol, M., Alcamo, J., & Hulme, M. (1996). Future availability of water in Egypt: The interaction of global, regional and basin scale driving forces in the Nile basin. Ambio, 25(5), 336–342. Falkenmark, M. (1995). Coping with water scarcity under rapid population growth. Paper presented at the Conference of SADC water ministers, Pretoria, 23–24 November. Gardner-Outlaw, T., & Engelman, R. (1997). Sustaining water, easing scarcity; a second update. Washington DC: Population Action International. Gleick, P. (1999). The human right to water. Water Policy, 1(5), 487–503. Heyns, P. (1995). Existing and planned water development projects on international rivers within the SADC region. Paper presented at the Conference of SADC water ministers, Pretoria, 23–24 November. Leemans, R., & Cramer, W. P. (1991). The IIASA database for mean monthly values of temperature, precipitation and cloudiness on a global terrestrial grid. Laxenburg: International Institute for Applied Systems Analysis. McCaffrey, S. C. (1993). Water, politics and international law. In P. H. Gleick (Ed.), Water in crisis; guide to the world’s water resources. Oxford: Oxford University Press. McCaffrey, S. C. (1998). The UN Convention on the Law of the Non-Navigational Uses of International Watercourses: prospects and pitfalls. In: S. M. A. Salman & L. Boisson de Chazournes (Eds.), International watercourses, enhancing cooperation and managing conflict. World Bank Technical Paper No. 414. Washington DC: The World Bank. Postel, S. (1992). Last oasis, facing water scarcity. New York: W.W. Norton. Savenije, H. H. G. (1997). Determination of evaporation from a catchment water balance at a monthly time scale. Hydrology and Earth System Sciences, 1(1), 93–100. Savenije, H. H. G., & van der Zaag, P. (2000). Conceptual framework for the management of shared river basins, with special reference to SADC and EU. Water Policy, 2(1–2), 9–45. Seyam, I. M. (1999). Algorithms for water resources distribution in international river basins. M.Sc. Thesis. IHE, Delft. USGS (2000). Hydro1k elevation derivative database. EROS Data Centre, US Geological Survey. http://edc.usgs.gov/ landdaac/gtopo30/hydro/ Whittington, D., Waterbury, J., & McClelland, E. (1994). Towards a new Nile waters agreement among riparians. Ethioscope, 1, 11–17. Wolf, A. T. (1999). Criteria for equitable allocations: The heart of international water conflict. Natural Resources Forum, 23(1), 3–30. Wouters, P. (1997). Present status of international water law. In: P. Wouters (Ed.), International water law; selected writings of Prof. Charles B. Bourne. London: Kluwer Law International.