Article 20

20.1 Commentary

The need to protect and preserve ecosystems is increasingly recognised throughout the world. Major consumptive uses, such as irrigation, municipal or industrial uses; and non-consumptive uses, including hydropower and navigation, constitute direct drivers of ecosystem degradation.307 The Millennium Ecosystem Assessment (MEA) estimated that water withdrawn from inland waters system has increased by at least 15 times over the past two centuries, with humans now controlling and using more than half the world’s accessible runoff.308 Increased uses of water have also impacted on water quality, with major pollutants, such as nutrients, heavy metals, nitrogen, organic compounds, suspended participles, contaminants and salinity, affecting aquatic ecosystems.309 In this regard, the World Water Commission has estimated that half of the world’s major rivers are seriously polluted.310Article 20, described as, ‘a simple, but potentially powerful, provision’, seeks to address the challenges faced by the existing and potential degradation of ecosystems of international watercourses.311 The provision, modelled on Article 192 of the UN Law of the Sea, sets out a general obligation on states to protect ecosystems of international watercourses,312 and is considered to reflect an emerging principle of customary law.313

When drafting the text of the UN Watercourses Convention, the ILC preferred the term ‘ecosystem’ over ‘environment’ as they felt that the latter term could be interpreted quite broadly; thus covering areas that ‘have minimal bearing on the protection and preservation of the watercourse itself’.314 An ‘ecosystem’ was defined by the ILC as being ‘an ecological unit consisting of living and non-living components that are interdependent and function as a community’315 (additional definitions).

Article 20 requires watercourse states to ‘protect’ and ‘preserve’ the ecosystems of international watercourses. The obligation to ‘protect’ ecosystems of international watercourses’ can be seen as an extension of Article 5 of the Convention, plus the obligation that states must use and develop an international watercourse, ‘in a manner that is consistent with adequate protection thereof’ (Article 5 (1)). Adequate protection encompasses measures relating to conservation, security, and water-related disease, as well as technical and hydrological ‘control’ mechanisms, such as the regulation of flow, floods, pollution, erosion, drought and saline intrusion.316 Some of these aspects, such as pollution and regulation of flow, are covered in more detail in other sections of Part IV of the Convention. Additionally, the obligation to protect includes the duty to shield ecosystems from a significant threat of harm.317 Inherent in the notion of protection is therefore the need to adopt a precautionary approach. Such an approach provides that where there are threats of serious or irreversible damage, lack of full scientific certainty cannot be used to justify not imposing cost-effective measures to prevent environmental degradation.318 Pursuant to the precautionary principle, a proportionate approach should be adopted that weighs up the degree of harm vis-à-vis the level of scientific certainty. Where full scientific certainty is lacking, but the degree of harm is potentially imminent, serious or irreversible, precautionary measures might therefore be justified.319 The precautionary principle is widely reflected in treaty practice related to transboundary harm.320

The obligation to ‘preserve’ ecosystems of international watercourses applies to freshwater ecosystems in a ‘pristine or unspoiled condition’,321 and can be seen as subordinate to the obligation to protect. Schwebel introduced the notion within the work of the ILC through his discussion of ‘wild and scenic watercourses’.322 He noted that preservation ‘involves the setting aside of a portion, or the entirety, of a stream, selected for its aesthetic beauty or its condition of being relatively unmodified by man: the native flora and fauna are typically abundant. Such free- running and unspoiled watercourses, so designated, will thus still be able to be experienced by future generations’.323 Schwebel therefore proposed that, ‘the Commission’s articles on the non-navigational uses of international water-courses could be cast in such a way as to contemplate this emerging practice and to comprehend such preservation regimes as an element of a State’s equitable participation in the development, use, protection and control of international watercourse systems’.324

However it should be noted that, on the basis of equity, the ultimate decision whether or not to preserve a particular ecosystem in a ‘pristine or unspoiled condition’ will be weighed against all relevant factors, including the social and economic needs of watercourse states. In weighing up such factors, Utton and Utton point out that, ‘for many states, the preservation of wild and scenic watercourses would prove too great a development sacrifice’.325 However, the latter authors also point out that, ‘where politically feasible, such a strategy should be employed to protect what few unspoiled stretches of rivers remain today. Depending upon the usages allowed under a wild and scenic watercourse regime, the economic advantages of a pristine river system may make up for the sacrificed developmental usages’.326 Recognition of the economic benefits of ecosystems is embodied in the notion of ‘ecosystem services’ (Figure 4.1). Adopting such an ecosystem services approach (see opposite column) may even provide alternative financial incentives through the concept of payment for ecosystem services. For instance, Sadoff and others observe that: ‘While payment for ecosystem services is increasingly popular in national contexts, it has not yet been pursued as a strategy in financing or developing transboundary water management institutions. One possible avenue from a developing country perspective is to label the outcomes of cooperative management as international public goods – in terms of positive environmental outcomes, regional security or other factors – for which international, non-basin actors could choose to contribute. Such a ‘payment for ecosystem and security services’ approach could help move financing from the paternalistic donor-recipient model to a service provider-customer model made up of equal partners. However, it is critical that a broad range of local stakeholders are involved in the decision-making process to ensure that the resulting agreements and financial flows have broad support’.327

Central to the protection of ecosystems of international watercourses is the concept of ‘environmental flows’.328 While Article 20 does not explicitly mention environmental flows, the need to ‘ensure stream flows adequate to protect the biological, chemical, and physical integrity of international watercourses, including their estuarine zones’329 can be considered as inherent in the obligation to protect ecosystems of international watercourses. Considerable treaty practice and international policy has reflected the notion of environmental flows.330 For instance, the 2002 Inco-Maputo Agreement provides details pertaining to flow regimes, and recognises, ‘the need to ensure water of sufficient quantity with acceptable quality to sustain the watercourse and their associated ecosystem’.331 Also the 1995 Agreement on the Cooperation for the Sustainable Development of the Mekong River Basin obliges states to maintain, ‘acceptable minimum monthly flows’ to protect the ecological integrity of the Mekong.332 Additionally, the need to protect ‘environmental flows’ can be found in national legislation. For instance, the 1998 South African Water Act utilises the concept of the ‘reserve’, which is defined as being, ‘the quantity and quality of water required … to protect aquatic ecosystems in order to secure ecologically sustainable development and use of the relevant water resource’.333 

A further important aspect of Article 20 is the inclusion of the phrase, ‘individually and, where appropriate, jointly’. This phrase recognises that in certain circumstances, states will not be able to act alone in protecting the ecosystem of international watercourses, but must work with states sharing a particular watercourse on an equitable basis. The requirement to act jointly where appropriate can therefore be seen as an extension of the obligation contained in Article 5(2) for watercourse states to, ‘participate in the use, development and protection of an international watercourse in an equitable and reasonable manner’; and the requirement under Article 8 that watercourse states cooperate in order to attain optimal utilisation and adequate protection of international watercourses.’ 334 In summarising this obligation, the ILC stipulates that: ‘The duty to participate equitably in the protection and preservation of the ecosystems of an international watercourse is not to be regarded as implying an obligation to repair or tolerate harm that has resulted from another watercourse state’s breach of its obligations under the draft articles. But the general obligation of equitable participation demands that the contributions of watercourse states to joint protection and preservation efforts be at least proportional to the measure in which they have contributed to the threat or harm to the ecosystems in question’.335 Joint action may therefore be necessary within the case of contiguous watercourses, but may not be required where the cause and effect of a particular use can be solely attributable to one watercourse state.

A further issue that should be considered in connection with Article 20 is the extent of the obligation to protect. Article 20 is ‘not qualified’, unlike Article 7, Article 21 or Article 22 for example, which make reference to ‘other watercourse states’. A question arising is therefore whether the obligation to protect ecosystems under Article 20 would apply where such harm only arises in one states, or whether there is more harm to the ecosystems of other states sharing a particular international watercourse.336 Most commentators believe that Article 20 should be interpreted as being consistent with the overarching principles of Articles 5-7. Article 20 is therefore considered an obligation to exercise due diligence to protect and preserve water ecosystems.337 Tanzi and Arcari therefore claim that, ‘although no express indication is provided either in Article 20, or in the relevant ILC commentary, it may be excluded that this obligation is one of an absolute character.’338 In this regard, the ILC’s commentary to Article 21(2) states that, ‘as with the obligation to “protect” ecosystems under Article 20, the obligation to prevent pollution “that may cause significant harm” includes the duty to exercise due diligence to prevent the threat of such harm’.339

An additional aspect which is important to point out is the implication of the obligation. McCaffrey maintained that, ‘there would seem to be little danger of states making frivolous claims in respect of this obligation, despite the lack of a requirement of resulting transboundary harm. States do not normally make claims against other states unless they consider that they have been injured or are threatened, and there is no reason to believe that their behaviour in respect of this obligation would be any different’.340 Along similar lines, a causal link must be established between a state’s activities and the existing or potential damage. The ability of states to prove ecosystem damage, which may not necessarily manifest itself immediately, might also act as a barrier to states making claims against other states.341

307 B Aylward, and others, ‘Freshwater Ecosystem Services’, in R Hassan, R Scholes and A Neville, Ecosystems and Human Well being: current state and trends (Island Press 2005), 216.

308 Ibid.

309 Ibid.

310 World Water Commission, A Water Secure World: Vision for Water, Life and the Environment (World Water Council 1999), at 13.

311 SC McCaffrey, ‘An Overview of the U.N. Convention on the Law of the Non-navigational Uses of International Watercourses’ (2000) 20 Journal of Land Resources and Environmental Law 57, 66.

312 UN Convention on the Law of the Sea (adopted 10 December 1982, entered into force 16 November 1994) (1994) 21 International Legal Materials 1261: Article 192 provides that, ‘States have the obligation to protect and preserve the marine environment’.

313 See McCaffrey, ‘An Overview of the U.N. Convention on the Law of the Nonnavigational Uses of International Watercourses’, at 70.

314 1994 Draft Articles at 119.

315 Ibid.

316 Ibid.

317 Ibid.

318 Declaration of the UN Conference on Environment and Development (Rio de Janeiro) (13 June 1992) UN Doc A/CONF.151/26 (Vol I).

319 P Sands, Principles of International Environmental Law (2nd edn, Oxford University Press 2003), 269.

320 Owen McIntyre, Environmental Protection of International Watercourses under International Law (Ashgate 2007), 265-283. McIntyre observes that the principle is likely to represent customary international law, given its ‘prevalence … in recent environmental treaties, declarations and resolutions as well as its inclusion in the Rio Declarations and the UNCED treaties’, 272.

321 Ibid.

322 ILC, ‘Third Report on the Law of the Non-navigational Uses of International Watercourses, by Mr Stephen M Schwebel, Special Rapporteur’, UN Doc A/CN.4/348 and Corr. 1, 190.

323 Ibid.

324 Ibid.

325 Albert E Utton and John Utton, ‘Adequate Stream Flows’ in Slavko Bogdanovic (ed), International Law of Water Resources – Contribution of the International Law Association (1954-2000) (Kluwer Law International 2001), 405.

326 Ibid.

327 C Sadoff, T Greiber, M Smith and G Bergkamp, Share: managing waters across boundaries (IUCN 2008), 78.

328 O McIntyre, Environmental Protection of International Watercourses under International Law (Ashgate 2007), 292.

329 AE Utton and J Utton, ‘Adequate Stream Flows’, in Slavko Bogdanovic (ed), International Law of Water Resources – Contribution of the International Law Association (1954-2000), 387.

330 See J Scanlon and A Iza, ‘International Legal Foundations for Environmental Flows’, (2003) 14 Yearbook of International Environmental Law 81. See also Article 19 of the Draft International Covenant on Environment and Development, which stipulates that ‘parties must take all appropriate measures, in particular through conservation and management of water resources, to ensure the availability of a sufficient quantity of water to satisfy basic human needs and to maintain aquatic systems’, <> accessed 24 October 2011.

331 Tripartite Interim Agreement for Co-operation on the Protection and Sustainable Utilisation of the Water Resources of the Incomati and Maputo Watercourse (adopted 29 August 2002), Article 9, ‘the need to ensure water of sufficient quantity with acceptable quality to sustain the watercourse and their associated ecosystems’.

332 Agreement on the Cooperation for the Sustainable Development of the Mekong River Basin, Article 6, requires parties to provide for ‘acceptable minimum monthly flows’ to protect the ecological integrity of the Mekong.

333 National Water Act, No. 36 of 1998, 20 August 1998 <>,   accessed 24 October 2011.

334 Refer to Part II of the Online User’s Guide.

335 1994 Draft Articles at 119.

336 SC McCaffrey, ‘An Overview of the U.N. Convention on the Law of the Nonnavigational Uses of International Watercourses’, at 66.

337 Ibid, 66.

338 A Tanzi and M Arcari, The United Nations Convention on the Law of International Watercourses (Kluwer Law International 2001), 246. See also O McIntyre, ‘The Emergence of an ‘Ecosystem Approach’ to the Protection of International Watercourses under International Law’ (2004) 13(1) Review of European Community and International Environmental Law 1, 9.

339 1994 Draft Articles at 291.

340 SC McCaffrey, The Law of International Watercourses (2nd edn, Oxford University Press), 459.

341 D Tarlock, ‘Ecosystems’, in D Bondansky, J Brunnée and E Hey, (eds.), The Oxford Handbook of International Environmental Law (Oxford University Press 2007), 583.

Figure 4.1 - Ecosystem Services and Rivers (Source UK MEA 2011) Figure 4.1 Ecosystem Services and Rivers (Source UK MEA 2011)

An Ecosystem Services approach

The Millenium Ecosystem Assessment (MEA) identifies a range of services that ecosystems provide including provisioning, supporting, regulating and cultural services (Millennium Ecosystem Assessment, Ecosystems and Human Well-being: A Framework for Assessment (Island Press 2003)). Water-related ecosystems services are defined by the UNECE to include:

‘…services such as flood prevention, control and mitigation; regulating runoff and water supply; improving the quality of surface waters and groundwaters; withholding sediments, reducing erosion, stablilising river banks and shorelines and lowering the potential of landslides; improving water infiltration and supporting water storage in the soil; and facilitating groundwater recharge. Water-related ecosystem services also include cultural services, such as recreational, aesthetic and spiritual benefits of forests and wetlands’ (UNECE, Recommendations on Payments for Ecosystem Services in Integrated Water Resources Management, available at <…/PES_Recommendations_web.pdf>, accessed 30 April 2012).

The advantage of an ecosystem services approach is that it provides a powerful instrument by which to justify the protection of ecosystems. As noted by Salzman, ‘while a wetland surely provides existence and option values to some people, the benefits provided by the wetland’s nutrient retention and flood protection services are both universal and undeniable. Tastes may differ over beauty, but they are in firm accord over the high costs of polluted water and flooded homes’ (James Salzman, Barton H. Thompson Jr and Gretchen C Dailey, ‘Protecting Ecosystem Services: Science, Economics and Law’ (2001) 20 Stanford Environmental Law Journal 309, 312). Similarly, Tarlock observes that, ‘much energy has been devoted to the development of environmental ethics, but the strongest case for environment protection can be justified by hard numbers’; and ‘because ecosystem services provision is either tied to a market or to government subsidies, it can be a fair and equitable way of reallocating resources’ (Dan Tarlock, ‘Ecosystem Services in the Klamath Basin: Battlefield Causalities or the Future?’ (2007) Journal of Land Use 207, 217).

An ecosystem services approach has yet to become widely implemented within the context of international watercourses, however, examples of such an approach do exist within the context of the Red River, the Okavango Rive and the La Plata Basin (see Dimple Roy, Jane Barr and Henry David Venema, Ecosystem Approaches in Integrated Water Resources Management – A Review of Transboundary River Basins (UNEP 2011)).

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