Inter-basin water transfer
An inter-basin water transfer is the abstraction of water from a river basin A and
move it – through pipelines, canals or bulk transport (for example, by lorry or
ship) – to another river basin B. According to the blue water footprint definition,
moving water away from a river basin is a blue water footprint within that basin,
because it is ‘consumptive water use’. The blue water footprint of the total transfer
will be allocated to the beneficiaries of the water in the receiving river basin.
Thus, processes in basin B that use water from another basin A have a blue water
footprint located in basin A, the size of which is equal to the amount of water
they receive plus the possible losses on the way. If the water users in the receiving
river basin B return (part of ) the used water to their own basin, we see that
water is ‘added’ to the water resources in river basin B. This ‘added’ water may
compensate for the blue water footprint of other users that have consumed water
from basin B; in that sense one may argue that the inter-basin water transfer creates
a ‘negative blue water footprint’ in the receiving river basin (insofar as the water
does not evaporate and indeed adds to the water system of the receiving basin).
The negative blue water footprint in basin B partly compensates the positive blue
water footprint of other users in basin B. Note that it does not compensate for the
blue water footprint in river basin A! When the goal is to assess the overall water
footprint of humans in basin B, we recommend to include a possible ‘negative
blue water footprint’ that exists as a result of real water transfer into the basin
(provided that it indeed compensates for a positive blue water footprint in the
basin in the same period). In the case of water footprint accounts for individual
processes, products, consumers or producers, one should leave calculated negative
blue water footprints out of the footprint accounts in order to make a clear
separation between the discussion about the gross water footprint of a process,
product, consumer or producer and the discussion about possible compensation.
The issue of compensation (subtractability) is debatable and should be dealt with
separately from the accounting phase. It has been argued that doing good in one
basin (for example, through a negative blue water footprint in that basin) cannot
compensate for the positive blue water footprint in another basin, since water
depletion and resulting impacts in one place will not be solved by adding water
somewhere else. In this case, adding a calculated negative blue water footprint to
the calculated positive blue water footprint would result in a misleading figure.
Read more on the impossibility to compensate a water footprint in one basin by
adding water in another basin in Chapter 5 (Box 5.2).