Updates to the 2010 RPA Water Assessment
The following three studies are planned:
Analysis of adaptation options in light of projected water supply shortages
Using the modeling framework of the 2010 Water Assessment, we will examine the effect on projected water supply shortages of a set of adaptation measures including additional reservoir shortage, new trans-basin diversions, and reductions in the drivers of water demand.
Enhanced national assessment of future water supply vulnerability
Changes from the 2010 assessment will include: (1) a finer spatial scale (the 204 4-digit basins of the contiguous U.S.), (2) a finer temporal scale (monthly), (3) a different water yield model (VIC), (4) updated estimates of demand for water in the agricultural and thermoelectric sectors, and (5) a different set of scenarios and GCMs. The downscaled estimates of climate variables are taken from the CMIP5 (Coupled Model Intercomparison Project Phase 5) website. The seven GCMs and the related scenarios are as follows:
| GCM | Scenarios |
| CSIRO Mk3.6.0 | RCP 26, 45, and 85 |
| BCC-CSM1.1 | RCP 26, 45, 60, and 85 |
| CanESM2 | RCP 26, 45, and 85 |
| GFDL-ESM2M | RCP 45, 60, and 85 |
| IPSL-CM5A-LR | RCP 26, 45, 60, and 85 |
| MIROC-ESM | RCP 26, 45, 60, and 85 |
| MPI-ESM-LR | RCP 26, 45, and 85 |
The RCP (representative concentration pathways) scenarios represent four possible greenhouse gas concentration trajectories adopted by the IPCC for its Fifth Assessment Report. They correspond to increases in global radiative forcing, from preindustrial times to 2100, of 2.6, 4.5, 6.0, and 8.5 W/m2. Data for many GCMs are available at the CMIP5 site. Among the criteria we used for selection of the seven GCMs we chose is that they provide data needed for implementing the VIC hydrologic model.
Future water supply vulnerability in the Colorado River Basin
Employing the enhanced framework summarized above, we will include a detailed analysis of water demands obtained using a CGE (computable general equilibrium) framework for the Upper Colorado River Basin. This study will allow a more nuanced projection of water supply shortages and analysis of adaptation options.
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