THE APPLICATION OF A STATISTICAL DOWNSCALING PROCESS TO DERIVE 21{sup ST} CENTURY RIVER FLOW PREDICTIONS USING A GLOBAL CLIMATE SIMULATION

Abstract

Executive SummaryThe ability of water managers to maintain adequate supplies in coming decades depends, in part, on future weather conditions, as climate change has the potential to alter river flows from their current values, possibly rendering them unable to meet demand. Reliable climate projections are therefore critical to predicting the future water supply for the United States. These projections cannot be provided solely by global climate models (GCMs), however, as their resolution is too coarse to resolve the small-scale climate changes that can affect hydrology, and hence water supply, at regional to local scales. A process is needed to 'downscale' the GCM results to the smaller scales and feed this into a surface hydrology model to help determine the ability of rivers to provide adequate flow to meet future needs.We apply a statistical downscaling to GCM projections of precipitation and temperature through the use of a scaling method. This technique involves the correction of the cumulative distribution functions (CDFs) of the GCM-derived temperature and precipitation results for the 20 th century, and the application of the same correction to 21 st century GCM projections. This is done for three meteorological stations located within the Coosa River basin in northern Georgia, and is used to calculate future river flow statistics for the upper Coosa River. Results are compared to the historical Coosa River flow upstream from Georgia Power Company's Hammond coal-fired power plant and to flows calculated with the original, unscaled GCM results to determine the impact of potential changes in meteorology on future flows.

Effect of Climate Change on Watershed Runoff Flow - Upper Coosa River Basin Upstream From Plant Hammond

“…In this study, the watershed runoff model parameters were developed from Section 2. The runoff flows (hydrography) for the period 2040-2049 were calculated using downscaled meteorological data (Werth, 2011). The downscaling was performed using three GCMs i.e., the Goddard Institute of Space Studies (GISS) Model E, the Meteorological Research Institute (MRI) of Japan's model, and the Canadian Climate Center (CCC) model to provide hourly precipitation and temperature data for NWS Dalton, GA, Jasper, GA and Rome, GA.…”

“…The process for this study is discussed in two reports. In the first report (Part 1), future weather conditions are predicted by using a statistical technique to downscale future climate produced by Global Climate Models (GCMs) to a regional/local area (Werth, 2011). This second part (Part 2) estimates the watershed runoff flow based on the future climate generated in Part 1.…”