Page - 523 - in Book of Full Papers - Symposium Hydro Engineering

2.2. DATA Long-term daily temperature (T) and precipitation (P) time-series obtained from I.R. of Iran Meteorological Organization (IRIMO) and Iran Water Resources Management Company (IWRM Co.). To calculate the average T and P in each sub-basin arithmetic mean and Thiessen polygon method applied, respectively. 2.3. GCM-SCENARIO In order to project the future hydrological condition, two different GCMs were selected (ECHAM5-OM and HadCM3). Description of the applied GCMs is presented in table 1. Also three different SRES emission scenarios (Special Report on Emission Scenarios) of A1B, A2 and B1 were considered to project the future T and P for 2011-2030 (2020’s), 2046-2065 (2050’s) and 2081-2100 (2080’s) time horizons. Table 1 Description of the Global Climate Models and IPCC-AR4 SRES emission scenarios Research Centre GCM GCM Acronym Resolution SRES Scenarios Max-Planck Institute for Meteorology (Germany) ECHAM5-OM ECHAM5 1.9×1.9° A1B, A2, B1 UK Meteorological Office (UK) HadCM3 HadCM3 2.5×3.75° A1B, A2, B1 To downscale T and P under A1B, B1 and A2 SERS scenarios during 2020’s, 2050’s and 2080’s in the study area, the stochastic weather generator of LARS- WG were applied; that generates time-series based on the probability distribution of base period data and correlations between observations. The detailed description of LARS-WG can be found in Semenov (2007). 2.4. HYDROLOGICAL MODELING AND MODEL CALIBRATION AND VALIDATION The HBV-light, semi-distributed hydrological model is used to simulate the runoff in the Dez basin. This model simulates runoff with temperature, precipitation and evaporation inputs and contains snow routine, soil moisture routine, response function and routing routine. The detailed description of the HBV model structure and routines could be found on Seibert and Vis (2012). Prior to the application of the model it is necessary to calibrate its parameters. This is done through try and error procedure as recommended by Bergstrom (1992). 523