Humanitarian law is also designed to protect civilian objects, including those indispensable to the survival of the civilian population. Article 29 of the Convention on the law relating to the non-navigational uses of international watercourses [available on http://www.un.org/], adopted by the General Assembly of the United Nations in 1997, stipulates:

“International watercourses and related installations, facilities and other works shall enjoy the protection accorded by the principles and rules of international law applicable in international and non-international armed conflict and shall not be used in violation of those principles and rules”.

General protection under the law applicable to armed conflicts extends to more than international watercourses, and the four main prohibitions laid down in that law are worth noting:

the ban on employing poison or poisonous weapons; the ban on destroying, confiscating or expropriating enemy property; the ban on destroying objects indispensable to the survival of the civilian population; the ban on attacking works or installations containing dangerous forces.

The four prohibitions, to which should be added the provisions on environmental protection, are expressly mentioned in the instruments relating to international armed conflicts, and the last two are also laid down in the law applicable to non-international armed conflicts. Starvation as a method of warfare is explicitly prohibited regardless of the nature of the conflict, and the concept of objects essential for the survival of the civilian population includes drinking-water installations and supplies and irrigation works. Immunity for indispensable objects is waived only when these are used solely for the armed forces or in direct support of military action. Even then, the adversaries must refrain from any action which could reduce the population to starvation or deprive it of essential water.

https://casebook.icrc.org/case-study/water-and-armed-conflicts