MEASURING WATER USE IN A GREEN ECONOMY - UNEP

Measuring water use in a green economy
The following subsections provide details on
these methodologies.
4.1 Water registers
In most parts of the world, the development
of water availability and access registers is in
its infancy. The same is true of systems that
enable the efficient management of allocations
during times of scarcity.
Rather than developing registers and systems
in isolation from more general wateraccounting
arrangements, it is possible to
develop them so that they become the primary
source of information about how, where and
when water may be and is used.
It is then possible to construct registers and
systems that can be used to help introduce
water charging systems and develop
arrangements that allow the transfer of
entitlements and allocations from one user
to another. For these systems to work well,
however, there is a need for institutional rigour
and administrative arrangements that ensure
compliance with allocation arrangements.
In fully allocated systems, it is critical that
whenever one person is allowed to take more
water, parallel arrangements are put in place to
ensure that someone else takes less.
Systems built in this manner typically begin by
partitioning a water resource into a number
of ‘pools’ of differing allocation priorities.
Entitlements to access water allocated to
each pool are then distributed among users
or user groups. As the volume of water within
these pools is likely to change from season to
season, each entitlement is defined as a share
of any water allocated to the pool. Sustainable
diversion limits are set for each pool in a
manner that ensures that enough water is
set aside for conveyance, maintaining the
environment and meeting other needs.
4.1.1 Pools
The approach to defining each watermanagement
‘pool’ requires careful
consideration. For a surface water system, the
approach typically involves:
• a pool of sufficient size to maintain enough
base flows to convey water to the end of the
system (Poff et al., 2010). This base flow
provides benefits to all entitlement holders
and also for non-consumptive uses like
recreation and transport;
• one or more consumptive pools. In some
situations, it is appropriate to establish
pools of varying reliability, for example,
to give a city a much more reliable water
supply than a dairy farmer;
• when entitlement systems are put in
place, it is normally necessary to define
and manage flood waters and flood risks
outside the entitlement system;
• when a shared system is used to define
entitlements and the degree of compliance
with entitlements is high, it is possible to
use market arrangements to encourage
each group of users to manage risks
associated with climate change. However,
an appropriate governance mechanism
may be necessary to correct socially
iniquitous effects of the market.
Intense stakeholder dialogue and riskmanagement
arrangements are necessary
to ensure that all water users and relevant
stakeholders understand the complexity of the
hydrological system, including how rivers and
aquifers interact with each other or how adverse
climate change, or alterations of policy, are likely
to affect the value of their access entitlement
and allocations of water. System-wide planning
arrangements are needed to specify how water
is allocated to the environment and all other
users, and to each pool.
Good data is needed to prioritise water uses
efficiently and equitably: the Murray Darling
Basin in Australia provides one of several
examples (See Box 4.1).
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