There is now a large published literature on the strengths and weaknesses of downscaling methods for different climatic variables, in different regions and seasons. However, little attention is given to the choice of downscaling method when examining the impacts of climate change on hydrological systems. This review paper assesses the current downscaling literature, examining new developments in the downscaling field specifically for hydrological impacts. Sections focus on the downscaling concept; new methods; comparative methodological studies; the modelling of extremes; and the application to hydrological impacts.

Consideration is then given to new developments in climate scenario construction which may offer the most potential for advancement within the ‘downscaling for hydrological impacts’ community, such as probabilistic modelling, pattern scaling and downscaling of multiple variables and suggests ways that they can be merged with downscaling techniques in a probabilistic climate change scenario framework to assess the uncertainties associated with future projections. Within hydrological impact studies there is still little consideration given to applied research; how the results can be best used to enable stakeholders and managers to make informed, robust decisions on adaptation and mitigation strategies in the face of many uncertainties about the future. It is suggested that there is a need for a move away from comparison studies into the provision of decision-making tools for planning and management that are robust to future uncertainties; with examination and understanding of uncertainties within the modelling system. Copyright © 2007 Royal Meteorological Society

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Linking climate change modelling to impacts studies: recent advances in downscaling techniques for hydrological modelling

Climate Change 1995 is a scientific assessment that was generated by more than 1 000 contributors from over 50 nations. It was jointly co-ordinated through two international agencies; the World Meteorological Organization and the United Nations Environment Programme. The assessment was completed by the Intergovernmental Panel on Climate Change (IPCC) with a primary aim of reviewing the current state of knowledge concerning the impacts of climate change on physical and ecological systems, human health, and socioeconomic factors. The second aim was to review the available information on the technical and economic feasibility of the potential mitigation and adaptation strategies.

Climate Change 1995

Freshwater resources and their management

Managing water in rainfed agriculture—The need for a paradigm shift

Identification and quantification of the hydrological impacts of imperviousness in urban catchments: A review

Detecting changes in streamflow response to changes in non-climatic catchment conditions: farm dam development in the Murray–Darling basin, Australia

Raising water demands and insufficient freshwater resources are the main reasons of water conflicts in transboundary watersheds. Sustainable water allocation can be a resolution for water disputes as it addresses simultaneously economic, social and environmental benefits. In this paper, a multi-objective model is introduced, which leads to sustainable water allocation of transboundary watersheds taking into account all these three aspects. Five water allocation objectives are proposed for this model in which three of them address the social factors and others represent the economic and environmental preferences. The Compromise Programming technique is employed to solve the applied model to the Sefidrud Basin, Iran and several water allocation schemes are provided based on various weights combinations. The results of the model elucidate that the proposed model can allocate 83 percent of the Basin's water resources, to its stakeholders in a sustainable way while the environmental demand is satisfied. Sustainable water allocation requires the triple bottom line approach.Proposed multi-objective model covers economic, social, and environmental aspects.Our model focuses on water allocation of shared basins with competing stakeholders.We analysed the sensitivity of stakeholders to the objectives' weights.We applied the model to a real cases study to demonstrate its applicability.

Optimal water allocation through a multi-objective compromise between environmental, social, and economic preferences

The effects of climate change due to increasing atmospheric CO2 onthe major tributaries to the Swan River (Perth, Western Australia) have been investigated. The climate scenarios are based on results from General Circulation Models (GCMs) and 1000 year time series are produced using a stochastic weather generator. The hydrological implications of these scenarios are then examined using a conceptual rainfall-runoff model, CMD-IHACRES, to model the response of six catchments, which combine to represent almost 90% of the total flow entering the upper Swan River,and hence the Perth city urban area. The changes in streamflow varies considerably between catchments, exhibiting a strong dependence on the physical attributes of the catchment in question. The increase in the magnitudes of rare flood events despite significant decreases in mean streamflow levels found in some catchments emphasizes the importance of estimating changes in the nature of the precipitation (variance, length of storm and interstorm periods), along with changes in the mean, in climate change scenarios.

Hydrological impacts of climate change on inflows to Perth, Australia

Experience in northern Thailand suggests that rapid commercialisation of upland catchments can have significant, and often unpredictable, social, economic and biophysical impacts. The purpose of this paper is to describe a multi-disciplinary methodology that is being used to assess water resource management in northern Thailand. The methodology identifies and integrates contributions from biophysical, economic and socio-cultural disciplines in the development of a scenario-modeling Decision Support System (DSS). The key modeling 'unit' in the DSS is the 'Resources Management Unit' (RMU). The RMU situates the socially and economically constituted agricultural household (the main decision maker) in its biophysical environment. This paper describes the application of the methodology to a case study of water allocation between upstream and downstream villages in the small subcatchment of Mae Uam in northern Thailand. It concludes with an indication of the potential for the methodology to be applied in other catchments.Experience in northern Thailand suggest that rapid commercialisation of upland catchments can have significant, and often unpredictable, social, economic an biophysical impacts. The purpose of this paper is to describe a multi-disciplinary methodology that is being used to assess water resource management in northern Thailand. The methodology identifies and integrates contributions from biophysical, economic and socio-cultural disciplines in the development of a scenario-modeling Decision Support System (DSS). The key modeling 'unit' in the DSS is the 'Resources Management Unit' (RMU). The RMU situates the socially and economically constituted agricultural household (the main decision maker) in its biophysical environment. This paper describes the application of the methodology to a case study of water allocation between upstream and downstream villages in the small subcatchment of Mae Uam in northern Thailand. It concludes with an indication of the potential for the methodology to be applied in other catchments.

A framework for integrated catchment assessment in northern Thailand

This paper presents a method for determining the impact of farm dams on streamflows independent of changes in climate and other land-use. The method is comprised of two components: first, the assessment of the statistical significance of trends in streamflows independent of climatic variation, and secondly, the use of a simulation model to determine the proportion of the assessed trend which is attributable to the impact of farm dams. The method has been successfully applied to a number of catchments throughout Australia. Two case studies have been selected to illustrate its practical application, namely the Marne River catchment in South Australia and the Yass River catchment in New South Wales. The results obtained for these catchments indicate that the nature and magnitude of trends estimated by the two largely independent methods is entirely consistent with the documented changes in farm dam development and other land use changes. There would appear to be a direct correlation between the volume of farm dam development and the decrease in streamflow yield, such that for every 1 ML of farm dam development there is a corresponding decrease in streamflows of between 1 ML to 1.3 ML.

Sergei Schreider

Papers

Detecting changes in streamflow response to changes in non-climatic catchment conditions: farm dam development in the Murray–Darling basin, Australia

Optimal water allocation through a multi-objective compromise between environmental, social, and economic preferences

Hydrological impacts of climate change on inflows to Perth, Australia

A framework for integrated catchment assessment in northern Thailand

Identifying the Separate Impact of Farm Dams and Land Use Changes on Catchment Yield