The role of hydrological model complexity and uncertainty in climate change impact assessment

摘要

Little quantitative knowledge is as yet available about the role ofhydrological model complexity for climate change impact assessment. Thisstudy investigates and compares the varieties of different model response ofthree hydrological models (PROMET, Hydrotel, HSAMI), each representing adifferent model complexity in terms of process description, parameter spaceand spatial and temporal scale. The study is performed in the Ammerwatershed, a 709 km2 catchment in the Bavarian alpine forelands,Germany. All models are driven and validated by a 30-year time-series(1971–2000) of observation data. It is expressed by objective functions,that all models, HSAMI and Hydrotel due to calibration, perform almostequally well for runoff simulation over the validation period. Somesystematic deviances in the hydrographs and the spatial patterns ofhydrologic variables are however quite distinct and thus further discussed.Virtual future climate (2071–2100) is generated by the Canadian RegionalClimate Model (vers 3.7.1), driven by the Coupled Global Climate Model(vers. 2) based on an A2 emission scenario (IPCC 2007). The hydrologicalmodel performance is evaluated by flow indicators, such as flood frequency,annual 7-day and 30-day low flow and maximum seasonal flows. The modifiedclimatic boundary conditions cause dramatic deviances in hydrologic modelresponse. HSAMI shows tremendous overestimation of evapotranspiration, whileHydrotel and PROMET behave in comparable range. Still, their significantdifferences, like spatially explicit patterns of summerly water shortage orspring flood intensity, highlight the necessity to extend and quantify theuncertainty discussion in climate change impact analysis towards theremarkable effect of hydrological model complexity. It is obvious that forspecific application purposes, water resources managers need to be madeaware of this effect and have to take its implications into account fordecision making. The paper concludes with an outlook and a proposal forfuture research necessities.