Règle correspondante
Practice Relating to Rule 45. Causing Serious Damage to the Natural Environment
Section B. Environmental modification techniques
The Military Manual (2005) of the Netherlands states:
0466. While the prohibition of AP I [1977 Additional Protocol I] addresses the consequences of a method or means used, the Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (also known as the ENMOD Convention) takes a different approach to the environment. This Convention prohibits modification of the living environment (environmental modification techniques) in order to use the environment as a weapon. The threshold of application of this Convention is lower: the consequences must be widespread, long-lasting or severe (ENMOD Article I).
In the negotiations leading to the ENMOD Convention, the following explanations of the terms widespread, severe and long-lasting were accepted:
Widespread: the consequences should be noticeable over a surface area of several hundred square kilometres.
Serious: consequences leading to serious or marked disruption or damage of human existence, natural or economic sources of support, or other assets.
Long-lasting: consequences which are noticeable for a period of several months or around one season.
0467. Environmental modification techniques are defined as any technique for changing – through the deliberate manipulation of natural processes – the dynamics, composition or structure of the Earth, including its flora and fauna, lithosphere (the Earth’s crust), hydrosphere (water on Earth) and atmosphere, or of outer space (ENMOD Article II).
In the negotiations concerning the ENMOD Convention, the following examples were quoted:
provoking an earthquake or tsunami, disrupting the ecological balance of a region, changing weather patterns (clouds, precipitation, cyclones or tornados), changing the climate, the courses of rivers, the ozone layer or the ionosphere.
Thus the diversion of a river or construction of a dam will affect the river basin, thus having a long-lasting impact on water levels and weather conditions. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, §§ 0466–0467.