|The Convention applies to land-based activities taking place within the river basin, but only to the extent that such activities might be relevant for the use, protection, and management of an international watercourse. For example, where state A builds a tannery plant located a distance from an international watercourse, but toxic waste and chemical pollution from the plant are discharged onto the surrounding land which then filters through soil into a connected aquifer or is carried by surface runoff into an international watercourse. These activities may cause significant harm to riparian state B and will thus fall under the scope of the Convention.
Green water, another example of a land based water us activity covered by the UN Convention is the water stored in soil as soil moisture. Upstream state A changes the landscape within a section of an international river basin from natural vegetation to arable farming and cattle grazing. Removal of the natural vegetation increases the evaporation from the soil surface, and increases the level of soil erosion, which reduces the degree of infiltration capacity of the land and leads to greater overland flow. Downstream state B is affected by the changing land use practices through increased surface water run-off leading to greater risk and magnitude of floods, and also from rising sedimentation loads – which in turn reduces the storage capacity of its dam reservoirs. The latter scenario potentially falls within the scope of the Convention, particularly in relation to the requirement to utilise international watercourses in an equitable and reasonable manner, taking into account all relevant factors and circumstances, and the obligation to protect the ecosystems of an international watercourse.
But not all activities fall under the scope of the Convention. Acid Rain, for instance, is not covered by the Convention: say non-riparian State C has an industrial plant which emits nitrogen and sulphur gases into the Earth’s atmosphere – the gases then react with water vapour to produce ‘acid rain’, which then falls onto riparian state D, thereby polluting the watercourse of state D. This type of activity will not be covered by the Convention because the origin of pollution is not continuously traceable through the land based watercourse system or drainage basin and is instead traceable through the atmospheric water system, meaning it could have originated from a state in another continent.145
A further potential pollution scenario which is caused by anthropogenic allocation of atmospheric water is pollution from cloud seeding. This is not covered by the Convention, although it is provided for to a very limited extent in other legal frameworks at national and international level.146
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Relationship with UNECE Water Convention