Updated: Oct 7

Authored By:

Ms Begumhan Simsir

Junior Associate Editor, Legit


Water has been one of the elemental components of human life for centuries. Most of the human advancements have happened either because of or in relations with water. Today, water is more important than ever, as humanity faces a climate crisis which might change our governance of water. Even in our current situation, we could not find a shared understanding and solution to the problems concerning the water utilisation between different actors. Considering how the amount of water-related conflicts might increase in forthcoming years, it is an urgent issue to rethink the international water law and develop solutions that will include and benefit all.

This paper aims to study, analyse and understand the development of the international water law and its current situation as it is codified in international documents. A particular focus will be given to two of the most popular principles of international water law, which govern most of the conflicts in this field. Furthermore, this paper examines the detail of these principles and their interaction with each other. This paper seeks to summarise the core topics of the field and detect its shortcomings to make improvements possible.

Research Methodology

In the writing process of this paper, various sources were taken into account. The opinions and works of various scholars from all over the globe found in assorted books, journals, databases and research papers were studied. Additionally, the works of the relevant international committees and research centres were examined together with the international documents they affected and created. Two of the most relevant UN Conventions were also studied and included in this paper. With an all-encompassing methodology, this paper is finished with study, assessment and investigation dependent on different writings, legitimate legal sources and official websites. The structure of this paper is isolated into headings, and subheadings, for better understanding.


1. International Water Law

2. Principles of International Water Law

3. Equitable and Reasonable Utilisation Principle

4. No Significant Harm Principle

5. The Relation between the Principle of Equitable and Reasonable Utilisation and Principle of No Significant Harm

6. Conclusion

International Water Law

Water always is a vital part of human life. International waters became a topic of international law after the 19th century when bodies of water started being used in fields other than transportation. The states emerging after the secession and the water started being used in fields like agro-business and industry. The new actors and sectors benefiting from the waters naturally created conflicts of interests and eventually resulted in regional and international conflicts. Even though the topic of water and its usage has been addressed in various international political documents, it usually was limited to the right to passage and similar subjects prior.

The initial official step in the development of international water law was taken with the recognition of the “freedom of navigation principle” on shared rivers in the Vienna Congress in 1815. The said principle was repeated and expanded in various international documents and became a rule of the customary international law in 1929 River Oder Case. After the Second World War, the evolution of international water law gained speed. However, the ones working for this were not the riparian states or international organisations. The relevant international norms were created by international legal associations and international courts and tribunals. The awards of the 1941 Trail Smelter Arbitration and 1957 Lake Lanoux Arbitration together with 1949 Corfu Channel Case Judgement were critical in this process of development.

The principle of “no state can cause and/or permit its territory to cause serious environmental damage to any other state” was established in the Trail Smelter award. The Corfu Channel case affirmed the responsibility of states, in cases of acts that occur in their territory but are non-compliant with international law and cause damage to other states. Lake Lanoux Arbitration had highlighted the rights of downstream riparian states and the importance of observance and collaboration between downstream and upstream riparian states in the usage of shared waters.

The most prominent international legal associations who affected the evolution of this field were the Institute of International Law (IIL) and the International Law Association (ILA). IIL has been working on the topic of non-navigational uses of shared waters from the start of the twentieth century. The Madrid Declaration, which established the “no significant harm principle” was written by IIL in 1911. The ILA has begun working on the topics concerning international water law in the 1950s. Nevertheless, the organisation’s works have shaped and changed the field significantly. Another principle of international water law being a fundamental one today is the “principle of equitable utilisation” which was established in ILA’s 1966 Helsinki Rules on the Uses of the Waters of International Rivers. In time, Helsinki Rules were recognised as one of the most authoritative sets of rules regarding the protection and use of international watercourses. Furthermore, they were accepted as customary international law by the international community.

Both of these organisations’ works concerning the international water law gained recognition in the Preamble of the 1997 UN Watercourses Convention. ILA updated and extended Helsinki Rules under the name of Berlin Rules on Water Resources in 2004.

Principles of International Water Law

Majority of the principles governing the international water law were developed in the last two centuries as outcomes of bilateral and multilateral conflicts over the shared waters. One of the first principles was the concept of “absolute territorial sovereignty”, also known as Harmon doctrine, which does not put any limitations on states’ authority to use the international rivers in its territory and does not bind them with any international legal obligations. This theory does not allow the downstream riparian states any right to object the water usage of the upstream riparian State. It was developed by US Chief Prosecutor Judson Harmon and was used to solve the dispute between the US and Mexico in 1894-1895 on the utilisation of Rio Grande River. As expected, this theory was mostly accepted by the upstream riparian states.

Another one of the earlier theories was “absolute territorial integrity”, which recognised the downstream riparian states’ rights to object to upstream riparian states’ usage of the shared water. According to this theory, the downstream State had the right to demand the continuation of the natural flow of the water in their territories. This theory was highly criticised as it put only obligations to the upper basin states, and rights only to the lower basin.

The third theory was “limited territorial integrity/sovereignty” doctrine. Mentioned doctrine aimed every riparian State to have equal right to use the shared water, while not causing any significant damage to others.

The fundamental principles governing today’s international water law can be named as:'equitable and reasonable utilisation of shared watercourses', 'no significant harm principle' and 'prior notification of and consultation on planned measures with a transboundary impact'. All of the named principles can be found in the articles of the UN Watercourses Convention.

Equitable and Reasonable Utilisation Principle

This doctrine foresees all the riparian states of the transboundary water to utilise the said water inequity with reason, and for all riparian states to have equal rights on this water. Furthermore, it is the most recognised and used doctrine in a water-based conflict. The principle implies that all riparian states have equality of rights, but this does not mean that there will be an equal share of the benefits and uses of the watercourse. The principle emphasises that even though all states are sovereign in their territories, they still cannot do everything they want when it comes to the shared waters in their territories. The states are under the obligation to act equitably and reasonably. The principle does not mean that the quantity of water will be divided into equal shares or that each State will be entitled to utilise the water equitably.

The principle is also recognised and codified in the UN-Watercourses Convention (UNWC) and reads in Article 5 as follows:

“1. Watercourse States shall in their respective territories utilise an international watercourse in an equitable and reasonable manner. In particular, an international watercourse shall be used and developed by watercourse States with a view to attaining optimal and sustainable utilisation thereof and benefits therefrom, taking into account the interests of the watercourse States concerned, consistent with adequate protection of the watercourse.

2. Watercourse States shall participate in the use, development and protection of an international watercourse in an equitable and reasonable manner. Such participation includes both the right to utilise the watercourse and the duty to cooperate in the protection and development thereof, as provided in the present Convention.”[1]

Above mentioned article has brought a new perspective to the idea of equitable utilisation as the idea of cooperation between the riparian states to achieve the equitable and reasonable utilisation of the water was introduced to the international community. The UNWC was encouraging the states to cooperate by taking affirmative steps concerning the transboundary waters they shared, individually or collectively.

The definitions and scopes of “equitable and reasonable” are not clear enough by themselves, and they need to be determined in every case individually. Several relevant factors were determined in the UN Watercourses Convention to take into consideration to help the riparian states determine the equitable and reasonable share of the waters and encourage cooperation between the riparian states. These factors can be found under

Article 6 of the UNWC:

“1.Utilization of an international watercourse in an equitable and reasonable manner within the meaning of article 5 requires taking into account all relevant factors and circumstances, including:

(a) Geographic, hydrographic, hydrological, climatic, ecological and other factors of a natural character;

(b) The social and economic needs of the watercourse States concerned;

(c) The population dependent on the watercourse in each watercourse State;

(d) The effects of the use or uses of the watercourses in one watercourse State on other watercourse states;

(e) Existing and potential uses of the watercourse;

(f) Conservation, protection, development and economy of use of the water resources of the

watercourse and the costs of measures taken to that effect;

(g) The availability of alternatives, of comparable value, to a particular planned or existing use.

2. In the application of article 5 of paragraph 1 of this article, watercourse States concerned shall, when the need arises, enter into consultations in a spirit of cooperation.

3. The weight to be given to each factor is to be determined by its importance in comparison with that of other relevant factors. In determining what is a reasonable and equitable use, all relevant factors are to be considered together and a conclusion reached on the basis of the whole”.[2]

Although the list mentioned above enlightens the idea and elements of the “equitable and reasonable” utilisation of the water, it does not provide a particular method or a process, that could be used in a possible conflict. It also carries the risk of “equalisation” rather than “equitable” water allocation. The principle by itself also has the risk of allowing significant harm, in the case of when “inflicted the endeavour to achieve equitable and reasonable utilisation of an international watercourse.”

This doctrine was reminded by the International Court of Justice in its Gabcikovo-Nagymaros Project Dispute when the Court concluded that a state “basic right to an equitable and reasonable sharing of the resources of an international watercourse”. The same decision also showed the possible neglect of socio-environmental impacts such as environmental issues and climate crisis, when the Court failed to take into consideration, the outcomes and effects of the river diversion on the environment and the ecology of the region.

No Significant Harm Principle

The 'no significant harm principles' have its roots on the good neighbouring principle, or as it is known in Latin “sic uteretuoutalienum non laedas”, “use your own not to harm that of other”. In the light of international law, it also was interpreted as “a reflection of sovereign equality of states”. The said principle in the context of international water law is a result of the limited territorial sovereignty doctrine. The main idea of this principle is that the states' duties is to avoid causing significant harm to other riparian states in the utilisation of shared waters. For harm to be qualified as a significant one, the harm should objectively impair the use of others. In line with the rule of good neighbourliness, states are expected to tolerate minor disturbances and mere inconveniences. Similar to other few principles, the “no significant harm” has gained supremacy in time with the application. Furthermore, it is one of the cornerstone principles of international water law.

A state’s duty to do “no significant harm” is more of a due diligence obligation of prevention, than an absolute prohibition on cross-border harm. The mentioned principle is codified and clarified in Article 7 of the UNWC and reads as follows:

“1.Watercourse States shall, in utilising an international watercourse in their territories, take all appropriate measures to prevent the causing of significant harm to another watercourse States.

2. Where significant harm nevertheless is caused to another watercourse State, the States whose use causes such harm shall, in the absence of agreement to such use, take all appropriate measures, having due regard for the provisions of articles 5 and 6, in consultation with the affected State, to eliminate or mitigate such harm and, where appropriate, to discuss the question of compensation.”[3]

The duty to do “no significant harm” does not prohibit the possible harm that can be done as the harm is not preventable in every case. However, it carries the obligation to take appropriate measures within itself to minimise the possibility of happening of this said harm. This obligation is still relevant when the harm comes from natural reasons such as floods, desertification, erosion, drought or water-borne diseases. In the case significant harm still affects a riparian state, the State who caused the harm has to “take all appropriate measures, having due regard to different factors, in consultation with the affected State, to eliminate or mitigate such harm, and where appropriate, to discuss the question of compensation” according to the Article 7 of the UNWC. The “no significant harm” principle is also a vital norm in international environmental law.

As mentioned above, this principle is closely related to the limited territorial sovereignty theory, as it puts a limit on states’ freedom on the utilisation of transboundary waters with the reciprocal rights of other riparian states. However, as it is a limiting article for the upper riparian states, it is not very popular with them.

Principle of Prior Notification

States are under the obligation of informing and notifying fellow riparian states who might suffer from the “the implementation of planned measures which may have a significant adverse effect upon other watercourse States” before they take any measure or act affecting the shared waters. The principle was codified in Article 12 of the UNWC as follows:

“Before a watercourse State implements or permits the implementation of planned measures which may have a significant adverse effect upon other watercourse States, it shall provide those States with timely notification thereof. Such notification shall be accompanied by available technical data and information, including the results of any environmental impact assessment, in order to enable the notified States to evaluate the possible effects of the planned measures.”

The Relation between the Principle of Equitable and Reasonable Utilisation and Principle of No Significant Harm

There is a controversy on the application of these principles, especially in the choice-making process of which principle to use to solve the conflict at hand. Lower riparian states, in many cases, favour the 'no significant harm principle' as it provides them with a right to object and protection against the harmful activities of the upper riparian states. Upper riparian states, on the other hand, prefer the application of the 'equitable and reasonable utilisation principle' because this principle does not limit their activities as much as the 'no-harm principle'/former principal does. Moreover, it gives them more scope to utilise their share of the transboundary water.

However, this does not mean that the principles are not to be applied together. There have been various international legal works and reports that tried to find a consensus application that would be accepted by both upper riparian and lower riparian states while benefiting both and minimising conflicts on the topic of international shared waters.

The debates on the priority of these principles went on the International Law Commission for 23 years. Every rapporteur who worked on the issue made a different remark and prioritisation or equation of the principles. In the current situation, it will not be wrong to say that the international community favours the 'equitable and reasonable utilisation principle' over the 'principle of no significant harm'. None of the principles is openly prioritised in the UNWC, but scholars seem to point out that with the interpretation, the priority of the first one can be read from the Convention. Similarly, the principle of equitable and reasonable utilisation has been recognised as the fundamental guiding principle of the UNWC in the Helsinki Rules.

Even the International Court of Justice, in its previously mentioned Gabcikovo-Nagymoros Case, emphasised the principle of equitable and reasonable use but did not reference the principle of no significant harm. A more significant issue arises when significant harm comes from equitable and reasonable use of transboundary water. States should put an effort to prevent potential significant harm to other riparian states as an obligation of conduct when they establish and act on equitable and reasonable utilisation method. Nothing more is expected of the State, because, the primary principle is the equitable and reasonable use/utilisation. As previously mentioned, in case of significant harm, the causing State is expected to compensate the affected riparian State and mitigate the harm caused. The mitigation does not mean to stop the utilisation in this case, but to take all appropriate measures to make mitigation possible and compensate for the harm.


Even though transboundary water has been an essential part of human history for ages, the international water law is a considerably growing field, which still has its controversial topics and an issue in need of a solution. The principles of no significant harm and equitable and reasonable utilisation are the driving principles of the field. However, their interaction with each other is still a controversial topic. As both benefits, a different side of the conflict, their application in practice has raised many questions. In light of the climate crisis and the growing importance of water, all States must find a mutual solution to water relating conflicts with an environmental point of view. Considering that the risk of water wars is higher than it was at any point of history, international water law should be transformed from a field of disputes to a field of cooperation.


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[1] United Nations WaterConvention, Article 5

[2] UNWC, Art 6 [3] UNWC, Art 7 (plz follow a pattern whether it is Art. or Article or Art... and also follow the citation style) Legit Originals, Volume 1, Issue 1 (September 2020)

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