Climate and Hydrologic Change Assessment for Georgia

This article describes a climate change and hydrological impact assessment for several basins in Georgia. First, a new statistical technique, Joint Variable Spatial Downscaling (JVSD), is developed to produce high resolution gridded hydrological datasets for the Southeast US from 13 different Global Circulation Models (GCMs). A lumped conceptual watershed model (Georgakakos et al., 2010) is then employed to characterize the hydrologic responses under the historical climate and the future climate scenarios. The historical (baseline) assessment is based on climatic data for the period 1901 through 2009. It consists of running the hydrological models under historical climatic forcing (of precipitation and temperature) for the 109 year period from 1901 to 2009 (in monthly steps). The future assessment consists of running the Georgia watershed models under all A1B and A2 climate scenarios for the period from 2000 through 2099 (100 years) in monthly time steps. For the baseline scenarios and each of the 26 future climate scenarios (i.e., 13 A1B scenarios and 13 A2 scenarios), this study assesses the changes of both climate variables (i.e., precipitation and temperature) and hydrologic variables (i.e., soil moisture, evapotranspiration, and runoff) for each watershed. The results show that: (1) the 26 IPCC future climate scenarios (2000-2099) do not indicate any long term change in average precipitation; (2) the precipitation distribution is expected to “stretch” becoming wetter and drier than that of the historical climate; (3) temperature and potential evapotranspiration (PET) show consistently increasing historical and future trends; (4) soil moisture storage exhibits a declining trend historically and for future climates; and (5) watershed runoff, and thus river flow, exhibits a similar historical decline across all Georgia watersheds.