Untitled DocumentClimate Change Impacts on Southwestern Basins
Macro Theme Area:
Knowledge Transfer [Project ID: K53]
PI:
Juan Valdes
CO-PI(s):
N/A
Basin focus:
Regional SW, San Pedro
Specific area in
basin /
field sites:
N/A
Summary/Goals: A study in the San Pedro Basin combining climatic data series analysis with climate change projection and global circulation models aims at providing a basis for the inclusion of climatic variability scenarios into the Valley's decision and policy-making process. A preliminary assessment aiming to evaluate the climate change impacts on the water resources of the San Pedro Basin has been completed and the first paper published. Ongoing detailed research on the individual water balance components of the basin is continuing, namely on the Evapotranspiration of the Riparian Area and the Recharge in the Basin.
Distinct rivers with different hydrological regimes have been chosen, including the transboundary San Pedro River Basin, where this study begins and is most advanced. Evaluating climate change impacts in basins with different hydrologic regimes will provide a powerful insight on the degree of vulnerability of Arizona and Sonora watersheds to such changes. The emissions scenarios defined by the Intergovernmental Panel on Climate Change (IPCC) have been used as reference inputs for the climate change estimations. Changes in precipitation can result in significant changes in mountain-front recharge. The long term changes in the basin's water budget will be assessed using existing MODFLOW models of the San Pedro Basin.
Activities and outcomes during past year:
As an outcome in itself: methodology to spatially and seasonally downscale regional estimates of circulation models using principal components analysis and other numerical tools in order to fit the appropriate data requirements for an accurate hydrological study. In addition, the effects of hydrological changes on the riparian socio-ecological systems are evaluated through the lens of a cross-disciplinary approach with aims to support and inform local water policy actions.
The yearly evoultion of the San Pedro Water Balance has been modeled under the four representative Emission Scenarios (A1,A2,B1,B2) and using an ensemble of 17 GCM models to obtain a highest probability outcome as well as a range of uncertainty. A groundwater model for the basin has been run under these different forcings and simulated the evolution of the water balance from 2000 to 2100. Changes in Recharge, Riparian Evapotranspiration and Net Stream Gain are some of the numerical outcomes obtained from these modeling work.
The most important outcome of this project has been providing insights to the San Pedro Partnership on the range of impacts of climate change. This research has been widely diffused within the Upper San Pedro Partnership thanks to our links with its Technical Committe. More detailed insights on the evolution and behavior of riparian ET and basin recharge under warmer climates are currently being pursued.
Plans for the upcoming year:
An effort has been made to clearly present a broad range of results corresponding to different scenarios to water managers and policy makers. In facts, the potential climate change impacts on the hydrology of the San Pedro Basin will be included in the Decision Support System (DSS) model of the basin. This will allow the Upper San Pedro Partnership, a stakeholder consortium in the basin, to evaluate strategies to meet safe yield and cope with a changing water balance under future scenarios. A more detailed analysis regarding the seasonal impacts of climate change in the region is being pursued. Riparian Evapotranspiration and its changes due to increasing temperatures is being studied using historical ET data in three sites in the basin's riparian area. Changes in recharge due to seasonal rainfall and temperature changes are also being looked into.
