AQUA: A framework for integrated water policy analysis

Abstract

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.

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.