Climate change impacts on water resources in the southeastern U.S. – Can we adapt? Peter Caldwell USDA Forest Service, Eastern Forest Environmental Threat Assessment Center Raleigh, NC SWPBA Annual Meeting, November 2011

Climate change- The scientific basis IPCC AR4, 2007

Unprecedented rate of change IPCC AR4, 2007

The evidence of change IPCC AR4, 2007 Temperature Sea level Snow cover

IPCC AR4, 2007 “Global warming is unequivocal and primarily human-induced” USGCRP, 2009

Change Variability Variability v. Change Bottom of Hill (current climate) ‏

USGCRP Global Climate Change Impacts in the United States, 2009 Precipitation

USGCRP Global Climate Change Impacts in the United States, 2009 Temperature

Extremes: Drought USGCRP, 2009

Extremes: Heavy precipitation USGCRP, 2009

Global Circulation Models Coupled land & atmosphere models Global coverage Coarse resolution (e.g. 2° - ~100x100 km) Have Biases Spatial resolution Model parameterization Scale not appropriate for impact studies

Bias correction and downscaling Maurer, ° resolution (100x100 km) 1/8° resolution (12x12 km) Dynamic or statistical downscaling

Emission scenarios IPCC AR4, 2007

Predicted global temperature IPCC AR4, 2007

Temperature changes IPCC AR4, 2007 A1B Scenario, change in temp from mean, multi-model mean and range A1B Scenario, change in temperature from by , multi-model mean

Precipitation changes Annual precipitation change Number of models predicting increased precipitation IPCC AR4, 2007 A1B Scenario, change in precipitation from by , multi-model mean

Key Issues for the Southeast Heat-related stresses for people, plants, and animals Decreased water availability Sea-level rise, likely increase in hurricane intensity and storm surge Ecological thresholds likely to be crossed throughout the region USGCRP, 2009

US Forest Service: A Legacy Water Resources Management Organic Act of 1897 “…securing favorable conditions of water flows…” Weeks Law of 1911 “…..regulation of the flow of navigable streams or for the production of timber.” Sustained Yield Forest Management Act of 1944 “….. maintenance of water supply, regulation of stream flow, prevention of soil erosion, amelioration of climate, and preservation of wildlife.” National Forest Management Act of 1976 “…multiple use and sustained yield of the products and services obtained…the coordination of outdoor recreation, range, timber, watershed, wildlife and fish, and wilderness.”

The future of USFS water resources management

SupplyDemand Climate Landuse change Population Reservoir GW Infrastructure Economics J. Am. Water Resour. Assoc. 44:1441 – 1457, 2008 Water Supply Stress Index (WaSSI) Model

Water Balance ET = f(PET, LAI, PPT, SM) Q = PPT – ET +/-  S Carbon Balance GEP = f(ET) Re = f(GEP) NEE = Re - GEP Biodiversity BIO = f(ET) -Birds-Amphibians -Reptiles-Trees -Mammals-Vertebrates PPT ET Q GEP Re Watershed and Land Cover Based

Climate and Population Scenarios Baseline ( ) vs. Future ( ) Climate ScenarioPrecipitationPET CSIROMK2-B214% CSIROMK3.5-A1B5%11% HADCM3-B27%15% MIROC32-A1B8%19%

Simulated water yield

Predicted trend in water yield

Predicted trend in water yield

Simulated streamflow

Predicted change in flow by

Change in water demand by

Water Supply Stress Index (WaSSI) Water Stress: Average annual WaSSI ≥ 0.4 United Nations (Raskin et al., 1997) World Water Council (Alcamo, 2000; Cosgrove & Rijsberman, 2000) Vörösmarty et al., 2000 WaSSI = Demand Surface + Groundwater Supply

Mean WaSSI in

Predicted trend in mean annual stream temperature , mean among four scenarios Stream temperature changes

Sediment delivery changes Predicted change in rainfall erosivity (R) by 2050

What can we do? Mitigate Reduce carbon emissions Enhance carbon sequestration Adapt Enhance ecosystem resilience Enhance infrastructure resilience Embrace uncertainty “If mitigation is about carbon, then adaptation will be about water”

Peter Caldwell Thank you!