Water Resources Management - Practices of Irrigation and On-farm Water Management - page 175

5.4.2 Scales of Sustainability
If we maintain too broad an interpretation of sustainable development, it becomes
difficult to determine progress toward achieving it. In particular, concern only with
the sustainability of large river basins could overlook the unique attributes of partic-
ular local watershed economics, environments, ecosystems, resource substitution,
and human health. On the other hand, not every hectare of land or every reach
of every stream in watershed need be sustainable or self-sufficient. Even at river-
basin or regional levels, it may not be possible to meet the “needs” or demands
of even the current generations, if those needs or demands are greater than what
can be obtained on a continuing basis at acceptable economic, environmental, and
social costs. This highlights the need to consider the appropriate spatial scales when
applying sustainability criteria to specific water resources systems.
We also need to consider the appropriate temporal scales when considering the
sustainability of specific river basin water resource systems. The achievement of
higher levels of water resource system sustainability does not imply that there will
never be periods of time in the future in which the levels of welfare derived from
those systems decreases. Given the variations in natural water supplies - the fact that
floods and droughts do occur - it is impossible, or at least very costly, to design and
operate water resources systems that will never “fail.” During periods of “failure”
the economic benefits may in fact depend on these events. One of the challenges
of measuring sustainability is to identify the appropriate temporal scales in which
those measurements should be made.
Sustainability measures provide ways by which we can quantify relative levels
of sustainability. This can be defined in a number of ways. One way is to express
relative levels of sustainability as separate or weighted combinations of statistical
measures of various criteria that contribute to human welfare. These welfare criteria
can be economic, environmental, ecological, and social. For many criteria, the time
duration as well as the extent may be important.
5.4.3 Achieving Sustainability
In order to achieve sustainable development and protection of the environment in
the context of water management, the Dublin statement identified four principles
to guide action at local, national, and international levels. Each of these princi-
ples - an integrated approach, a participatory approach, explicit involvement of
women, water as an interconnected package - is the basis for sustainable water
management and development in the current twenty-first century. At least three
themes fundamental in Agenda 21, publication from the Earth Summit in Rio de
Janeiro, are directly relevant to water management and development. First, it was
argued that planning should be well informed, systematic, and rigorous. Second, it
was mentioned that more attention should be given to equity issues in the future.
And third, Agenda 21 consistently advocates a need for greater decentralization in