Article 21 of the UN Watercourses Convention addresses transboundary pollution, which is defined as being ‘any detrimental alteration in the composition or quality of the waters of an international watercourse which results directly or indirectly from human conduct’. The intention of this definition is to provide a general, factual definition which does not mention particular types of pollution or polluting agents.344 Additionally, the definition covers ‘any detrimental alteration’, leaving questions over the threshold of pollution under Article 21(2). Also, the types of detrimental effects, for example harm to human health, property, or living resources, are not explicitly listed in this definition.345 By focusing on a factual definition of pollution, rather than stipulating legal parameters, the approach adopted by the UN Watercourses Convention is consistent with the 1966 Helsinki Rules, which defines pollution as, ‘any detrimental change resulting from human conduct in the natural composition, content, or quality of the waters of an international drainage basin’346

In justifying a broad approach to the definition of pollution, the ILA felt that the nature and effect of pollutants are likely to change over time, so it was better to provide a broad definition, for example ‘any detrimental change resulting from human conduct’, irrespective of the effects on subsequent users347 - effects are covered in Article 21(2). The explicit reference to ‘human conduct’ in Article 21(1) is intended to distinguish between natural and anthropogenic changes, and refers to both acts and omissions, or failures to act.348

In obliging states to prevent, reduce and control pollution, ‘that may cause significant harm’; Article 21(2) incorporates pollution issues within the general substantive obligation to prevent significant harm contained in Article 7. Certain harm, even leading to significant pollution, may therefore be tolerated if the polluting watercourse state is making its ‘best efforts to reduce the pollution to a mutually acceptable level.’349 The rationale behind such a condition, is to prevent ‘undue hardship’ or inequitable results, whereby the detriment to the watercourse state experiencing harm is ‘grossly disproportionate’ to the benefit gained by the polluting watercourse state.350However, it should be remembered that the polluting watercourse state is still under an obligation to exercise ‘due diligence’ (see Glossary of Terms) in the reduction of pollution to an acceptable level, and ensure consistency with Article 20 and other obligations to protect the long-term viability of a renewable resource.

According to Article 21(2) states are obliged to ‘prevent’ new pollution, and ‘reduce and control’ existing pollution that may cause significant harm. The use of the term ‘may’ in Article 21(2) also recognises a precautionary approach (see Glossary of Terms).351

Article 21(2) goes further than Article 7 in one respect, namely that harm may be to ‘other watercourse States or to their environment’. As  stipulated in Article 21(2) such harm may include harm to ‘human health or safety’, or the use of water for any beneficial purpose. The choice of the term ‘environment’ – broader than the concept of ‘ecosystem’ – was used to cover impacts such as those on ‘the living resources of the watercourse’, ‘flora and fauna dependent upon the watercourse, and the amenities connected with it’.352

Like the obligation to protect the ecosystems of international watercourses under Article 20, Article 21(2) requires states to adopt joint measures ‘where appropriate’.353

Closely aligned with the obligation to take joint measures is the obligation ‘to take steps’ to harmonise policies relating to pollution. The obligation to harmonise policies, ‘addresses the problems that often arise when states adopt divergent policies, or apply different standards, concerning the pollution of international watercourses’.354 Article 21(3) expands on the need to harmonise polices relating to pollution between states by requiring that, watercourse states consult over joint measures, such as setting joint water quality objectives and criteria; establishing techniques and practices to address point and non-point source pollution; and establish a list of potentially dangerous substances.

The obligation contained in Article 21(3) is one of consultation, in good faith355 (see Glossary of Terms), consistent with the general obligation to cooperate. Although the establishment of such standards will often be critical to ensuring that the substantive obligations to prevent, reduce and control pollution are met.

342 UNEP and Pacific Institute, Clearly the Waters – A focus on water quality solutions (UNEP 2010).

343 Global International Waters Assessment, Challenges to International Waters – Regional Assessments in a Global Perspective (UNEP, 2006), 36-53.

344 1994 Draft Articles at 121.

345 Ibid.

346 Slavko Bogdanovic (ed), International Law of Water Resources – Contribution of the International Law Association (1954-2000), 109.

347 Ibid, 11.

348 Ibid, 111.

349 1994 Draft Articles at 122.

350 Ibid.

351 Also refer to Article 20

352 1994 Draft Articles at 122.

353 See Section 20.1.

354 1994 Draft Articles at 123.

355 Refer to Section 3.1.4.

Figure 4.2 The World Health Organisation Water Quality Standards

Water quality criteria, objectives and standards under the 1992 UNECE Water Convention

Water quality criteria: The UNECE Guide to implementation defines ‘water quality criteria’ as being, the ‘minimum concentration levels for oxygen and maximum concentration levels for substances in water that do not harm a specific single form of water use (e.g. drinking water use, use of water for livestock watering, irrigational water use, water use for recreational purposes, use of water by aquatic life)’. Water quality objectives are described as constituting a numerical concentration or narrative statement that has been established to support and protect designated uses of water.

Annex III of the 1992 UNECE Water Convention contains guidance on the establishment of water quality objectives and criteria, which should:

1. Take into account the aim of maintaining and, where necessary, improving the existing water quality;
2. Aim at the reduction of average pollution loads (in particular hazardous substances) to a certain degree within a certain period of time;
3. Take into account specific water-quality requirements (raw water for drinking-water purposes, irrigation, etc);
4. Take into account specific requirements regarding sensitive and specially protected waters and their environment e.g. lakes and groundwater resources;
5. Be based on the application of ecological classification methods and chemical indices for the medium- and long-term review of water quality maintenance and improvement;
6. Take into account the degree to which objectives are reached and the additional protected measures, based on emission limits, which may be required in individual cases.

The 1992 UNECE Water Convention also provides further guidance on ‘techniques and practices to address pollution from point and non-point sources’. Pursuant to the latter Convention, such techniques and practices include the establishment of water discharge limits based on best available technology; biological treatment or equivalent processes should be applied to municipal wastewater; appropriate measures should be taken, such as the application of best available technology, in order to reduce nutrient inputs from industrial and municipal sources; and appropriate measures and best environmental practices should be developed and implemented for the reduction of inputs of nutrients and hazardous substances from diffuse sources, especially where the main sources are from agricultures.

Annex I of the 1992 UNECE Water Convention defines ‘best available technology’ as being:

‘…the latest stage of development of processes, facilities or methods of operation which indicate the practical suitability of a particular measure for limiting discharges, emissions and waste. In determining whether a set of processes, facilities and methods of operation constitute the best available technology in general or individual cases, special consideration is given to:

1. Comparable process, facilities or methods of operation which have recently been successful tried out;
2. Technological advances and changes in scientific knowledge and understanding;
3. The economic feasibility of such technology;
4. Time limits for installation in both new and existing plants;
5. The nature and volume of the discharge and effluents concerned;
6. Low- and non-waste technology’

The Annex to the Convention goes on to comment that, ‘what is “best available technology” for a particular process will change with time in the light of technological advances, and economic and social factors, as well as in the light of changes in scientific knowledge and understanding.’ Additionally, the Annex to the Convention provides guidelines for development of best environment practices, thus stipulating that the following measures should be considered,

1. Provision of information and education to the public and to users about the environmental consequences of the choice of particular activities and products, their use and ultimate disposal;
2. The development and application of codes of good environmental practice which cover all aspects of the product’s life;
3. Labels informing users of environmental risks related to a product, its use and ultimate disposal;
4. Collection and disposal systems available to the public;
5. Recycling, recovery and reuse;
6. Application of economic instruments to activities, products or groups of products;
7. A system of licensing, which involves a range of restrictions or a ban.

When determining the suitability of such practices, factors that should be taken into account include:

1. the environmental hazard of the product, its production, use or ultimate disposal;
2. substitution by less polluting processes or substances;
3. scale of use;
4. potential environmental benefit or penalty of substitute materials or activities;
5. advances and changes in scientific knowledge and understanding;
6. time limits for implementation; and
7. social and economic implications.

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