"Life is not a quiet river!" one often hears it said. But are any rivers truly quiet? The natural flow of river water towards the seas and oceans provides an essential economic resource for the countries it crosses. Each State naturally seeks to reap the greatest possible benefit from these bodies of water. From the perspective of sustainable development, however, every country should be able to enjoy a share of this wealth without harming nations downstream or overexploiting the waterways that cross its territory. This is the purpose of Article 6 of the 1997 New York Convention on the Non-navigational Uses of International Watercourses, which entered into force in August 2014. The text specifies how the countries concerned must apply the rule of equitable and reasonable use set out in Article 5 of the same Convention. This entails considering every relevant element, including hydrological factors, the economic and social needs of the countries concerned, the size of their populations and the possible availability of other options that could replace direct use of river water (desalination plants for coastal nations).
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The decision-maker's choice is crucial --------------------------------------
Following these guidelines, a model can be constructed that takes thirteen factors into account: basin area, precipitation, internal renewable water resources, dependence on external water resources, water resources per capita (measured at two points in time), water withdrawal per capita, the size of the population with access to drinking-water sources, total population (measured at two points in time), a human development indicator, gross domestic product and total irrigated area. Taking measurements ten or eleven years apart introduces a dynamic, evolving element into the model.
Taking a large number of criteria into account certainly does not make the problem any easier to solve! Moreover, the assumptions underlying the relevant models could lead to significantly different results. The decision-maker's choice therefore becomes crucial. Several options are available. One is to use methods related to utility theory, such as MAUT (short for multi attribute utility theory, or multi-attribute utility theory). Another is to use so-called outranking methods, such as Electre (from the French for elimination and choice expressing reality), Promethee (short for preference ranking organisation method for enrichment evaluations, or the method for organizing and ranking preferences for enhanced evaluations) or Gaia (short for geometrical analysis for interactive assistance, that is, geometric analysis for interactive decision support).