climate change information for IWRM

Abstract

Integrated Water Resources Management often needs specific climate data, e.g. for water use assessment in agriculture or reservoir design for drinking water supply and flood retention. Needed data are often missing. Climate Change aggravates this problem, as in contrast to the past, measured data only are probably insufficient to be used inIWRMstudies for future impact.Ascheme is presented to replace measured data by climate model output. Model performance assessment is done for General Circulation Models (GCMs) with the example regions of Eastern Europe (Western Bug catchment), the Arabian Peninsula and the region of Brasília (Brazil). The ranking of GCMs was sensitive to region, performance measure and reference data. However, HADCM3 (Hadley Centre) and MPEH5 (MPI Hamburg) show a good resemblance with two differing references for two out of three regions. Regional downscaling is demonstrated with two examples: dynamical with the mesoscale CCLM for the Western Bug, statistical with the SDSM for Brasília. Both approaches differ in observational data requirements (lower for dynamical downscaling) and need for bias correction (more for dynamical downscaling). Impact modelling based on climate model output shows significant changes inSWAT simulations of runoff in the Western Bug catchment for the B1 and A2 scenarios at the end of the 21st century. Climate change is an IWRM relevant problem in all three regions, increasing evaporation of irrigated agriculture in the Middle East, changing soil erosion into drinking water reservoirs in central Brazil or the Bug runoff. Which climate information is adequate depends on many factors, primarily the specific IWRM problem.