Abstract
Abstract. General circulation models (GCMs) have been widely used to simulate current and future climate at the global scale. However, the development of frameworks to apply GCMs to assess potential climate change impacts on regional hydrologic systems, ability to meet future water demand, and compliance with water resource regulations is more recent. In this study eight GCMs were bias-corrected and downscaled using the bias correction and stochastic analog (BCSA) downscaling method and then used, together with three ET0 methods and eight different water use scenarios, to drive an integrated hydrologic model previously developed for the Tampa Bay region in western central Florida. Variance-based sensitivity analysis showed that changes in projected streamflow were very sensitive to GCM selection, but relatively insensitive to ET0 method or water use scenario. Changes in projections of groundwater level were sensitive to both GCM and water use scenario, but relatively insensitive to ET0 method. Five of eight GCMs projected a decrease in streamflow and groundwater availability in the future regardless of water use scenario or ET method. For the business as usual water use scenario all eight GCMs indicated that, even with active water conservation programs, increases in public water demand projected for 2045 could not be met from ground and surface water supplies while achieving current groundwater level and surface water flow regulations. With adoption of 40 % wastewater reuse for public supply and active conservation four of the eight GCMs indicate that 2045 public water demand could be met while achieving current environmental regulations; however, drier climates would require a switch from groundwater to surface water use. These results indicate a high probability of a reduction in future freshwater supply in the Tampa Bay region if environmental regulations intended to protect current aquatic ecosystems do not adapt to the changing climate. Broad interpretation of the results of this study may be limited by the fact that all future water use scenarios assumed that increases in water demand would be the result of intensification of water use on existing agricultural, industrial, and urban lands. Future work should evaluate the impacts of a range of potential land use change scenarios, with associated water use change projections, over a larger number of GCMs.
Highlights
The Intergovernmental Panel on Climate Change (IPCC) along with many other studies have indicated that climate change is likely to alter both the global hydrologic cycle and regional hydrologic cycles (Aalst et al, 2014; Déry et al, 2009; Georgakakos et al, 2014; Hawkins et al, 2014; Milliman et al, 2008)
The variance-based global sensitivity analysis was conducted for both the wet season (June–September) and the dry season (October–May) to evaluate the relative variation of projected changes in hydrologic response attributed to the choice of General circulation models (GCMs), choice of water use scenario, and choice of ET0 method
94.4 % of the variance of the change in wet season Hillsborough River streamflow in the future 1 period (2030–2060) is attributed to differences among GCMs, 0.2 % of the variance is attributed to differences among the ET0 method, and 1.6 % of the variance is caused by the water use scenario, respectively
Summary
The Intergovernmental Panel on Climate Change (IPCC) along with many other studies have indicated that climate change is likely to alter both the global hydrologic cycle and regional hydrologic cycles (Aalst et al, 2014; Déry et al, 2009; Georgakakos et al, 2014; Hawkins et al, 2014; Milliman et al, 2008). These studies have indicated that climate change is likely to increase the frequency of droughts, as well as the magnitude of floods in many regions (Diffenbaugh and Field, 2013; Georgakakos et al, 2014; Walsh et al, 2014). S. Chang et al.: Impacts of climate change and water use scenarios
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