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At what scales do climate variability and land cover change impact on flooding and low flows?

Abstract:

To provide a road map of how to address the issues of climate variability and land cover change impact on flooding and low flows, the working group has singled out a number of specific research questions. These are given below for each of the themes discussed above. Change and methods of change analysis: • What do various earth-sciences consider change? • How do they deal with it? • What are the results of agents of change on hydrological response, and time scales of change? • What are suitable methods of change analysis/detection? • When does the delta change approach (or incremental change approach) fail? Transitional climate regimes: • How can one best use climate model results in view of the scale gap? • How does uncertainty propagate from climate to hydrological models? • How can analyses by the analogue method be combined with results from climate models? • If circulation patterns change, does this decrease/increase floods? • How can one relate changes in the mean atmospheric characteristics to changes of the extremes? Catchment processes and flow paths: • How do land use change and climate variability modify flow pathways and storage? • What are the changes in soil structure due to vegetation changes (e.g. break-down of fabric, mineralogy)? • What are the changes in the time scales, e.g. over • what time scales does soil structure change occur in response to land cover change? • What is the resilience of soil hydraulic characteristics to change? • What is the recharge for different settings and how does it change with climate/land use changes? Feedbacks: • How do floods and low flows change with time and what are the feedback mechanisms controlling them? • What feedbacks of land cover/climate impacts on water resources exist? • What are the positive and negative feedback loops? • How does the water balance affect runoff components (interactions between long and short time scales)? • What are the changes in the coupling between groundwater and surface water linked with land cover change? Heterogeneity and scaling: • What percentage of catchment area can be changed to another land cover type before a significant change in the flood regime occurs? • How do changes in the soil's hydraulic characteristics due to vegetation changes transfer to larger scales? • How can one upscale local information on soils, vegetation, groundwater and groundwater-surface water interactions to the scale of HELP basins (10 000 km2)? • What are integrative concepts of upscaling/downscaling in the context of impact analyses? • What is the relative role of climatic variability and land cover change on floods and low flows as a function of scale in different environments? Generalization and potential of typologies: • How can climate/rainfall, catchments, aquifers, soils and vegetation be classified (with a view on floods and low flows)? • What processes switch between regimes (in time, spatially)? • How to best overcome data scarcity to assess the impacts on water resources due to land cover change, and what are the low-cost options for measuring hydrological response at various scales? • What is the necessary network density required to address a management problem such as the ecological consequences in a stream after catchment area development? • What variables should be strategically collected that would more directly address impact on hydrological response? Copyright © 2007 John Wiley & Sons, Ltd.