English Abstract In order to design water policy as part of a strategy
for sustainable development, an insight into the dynamics of the water
system is necessary but not sufficient. It is hypothesized that
understanding today's water policy issues requires integrated analysis of
hydrology, water quality, water demand and water supply in relation to land
use changes, soil degradation, element cycles and climate change, as well as
in relation to food and energy supply, human development and economics. The
analytical tools for water policy analysis presently available only partly
meet the requirements of such integrated analysis. To fill this gap, the
new modelling framework AQUA has been developed. AQUA is part of the more
extensive modelling framework TARGETS: a Tool to Assess Regional and Global
Environmental and health Targets for Sustainability. This report discusses
the policy issues to be dealt with by AQUA, the main structure of the tool
and the underlying definitions and assumptions. Since the aim of the report
is to provide a methodological outline, the preliminary results shown should
be considered no more than illustrative. AQUA consists of a simulation
model and a framework of indices linked to this model. The simulation model
describes the "pressures" on the water system, the dynamics of the water
system itself, the impacts on various socio-economic and ecological
functions of the water system and the societal responses to these impacts.
To enable the user of the model to analyse the effects of certain measures,
the model contains a set of policy variables, representing some of the major
policy options of the water policy maker. The hierarchical framework of
indices linked to the model aims at providing information to the policy
analyst at different levels of comprehensiveness. The generic framework of
AQUA has been elaborated for the world as a whole and for two specific river
basins: the Ganges-Brahmaputra Basin and the Zambezi Basin. The world model
starts simulating in the year 1900, the Ganges-Brahmaputra model in 1950 and
the Zambezi model in 1990. All models run through to 2100. Among the
outcomes of the simulations are time series for: the (stable) fresh water
availability, the depletion of fossil ground water, the distribution of the
total fresh water stock over four functional water quality classes, the
effects of climate change on the fresh water availability, water demands,
water supply efficiencies, actual supplies and supply costs, the percentages
of the population with proper water supply and sanitation, the area of
cropland irrigated and the fraction of the surface water meeting ecological
requirements. The world model also provides information on sea level rise,
its various causes and the coastal impacts. AQUA differs from other water
modelling frameworks in four respects. First, the tool is quite
comprehensive: it takes into account more water-related phenomena than do
most other tools. Besides, through integration within TARGETS, it can
support the development of water policy that is coherent with other
environmental and socio-economic policy. Second, the tool is relatively
simple in all its individual parts. For most of the submodels, especially
for the water system submodel, far more detailed models are available.
However, these generally require more data and have longer run times. A
third characteristic of AQUA is the link of a framework of indices to the
simulation model. In this way, the results of the model can be communicated
towards the user of the model in a more comprehensive way. Finally, a
fourth characteristic of AQUA is its genericity, i.e. applicability at
different spatial scale levels and with different degrees of spatial
differentiation. Although the modelling results are preliminary, they show
that the integrated and generic approach is feasible. The scientific
reliability of the results is presently being studied in more detail by
comparing the simulated historical values with observed data and by
analysing the processes simulated under varying assumptions, parameter
values and scenarios. Besides, the performance of the hydrological submodel
of the Ganges-Brahmaputra model is compared with the performance of a more
detailed grid-based runoff model of the Ganges-Brahmaputra Basin. Finally,
whether and how the mixture of characteristics of AQUA will benefit the
policy analyst in understanding today's water policy issues will be studied
more thoroughly during the coming year, if both the world model and the
river basin models will be used in the actual process of policy analysis
within the UNEP Earthwatch Programme.
Rapport in het kort
Voor het ontwikkelen van waterbeleid als onderdeel van
een strategie voor duurzame ontwikkeling, is het nodig om inzicht te hebben
in de dynamica van het watersysteem, maar dat is niet voldoende. Er wordt
gesteld dat we alleen vat kunnen krijgen op de huidige waterbeleidsproblemen
door het uitvoeren van integrale analyses met betrekking tot hydrologie,
waterkwaliteit en watervraag en -aanbod in relatie tot
landgebruiksveranderingen, bodemdegradatie, element cycli en
klimaatsverandering alsmede in relatie tot voedsel- en energievoorziening en
sociaal-economische ontwikkeling. De momenteel beschikbare
beleidsanalytische hulpmiddelen kunnen slechts in beperkte mate zulke
integrale analyses ondersteunen. Om deze leemte op te vullen is het nieuwe
model AQUA ontwikkeld. AQUA is onderdeel van het grotere modelraamwerk
TARGETS, een acroniem voor Tool to Assess Regional and Global Environmental
and health Targets for Sustainability. Het rapport bespreekt eerst de
beleidsvragen waarbij AQUA als analytisch hulpmiddel ingezet zou moeten
kunnen worden; vervolgens wordt uitgebreid ingegaan op de structuur van
AQUA en de onderliggende definities en aannamen. Het generieke raamwerk van
AQUA is geoperationaliseerd voor de wereld als geheel en voor de
stroomgebieden van de Ganges-Brahmaputra en de Zambezi. De voorlopige
resultaten van deze toepassingen laten zien dat de integrale benadering
haalbaar is. Het is de verwachting dat er inzichten kunnen worden verschaft
over de samenhang tussen water-gerelateerde problemen en andere
milieuproblemen en sociaal-economische vraagstukken die op de traditionele -
reductionistische - wijzen van analyse niet verkregen kunnen
worden.