- Projections of a drier, warmer climate in the U.S. Southwest would complicate
management of the Colorado River system – yet these projections, often based on coarse
resolution global climate models, are quite uncertain. We present an approach to understanding
future Colorado River discharge based on land surface characterizations that map the Colorado
River basin’s hydrologic sensitivities (e.g., changes in streamflow magnitude) to annual and
seasonal temperature and precipitation changes. The approach uses a process-based macroscale
land surface model (LSM; in this case, the Variable Infiltration Capacity hydrologic model,
although methods are applicable to any LSM) to develop sensitivity maps (equivalent to a simple
empirical model), and uses these maps to evaluate long-term annual streamflow responses to
future precipitation and temperature change. We show that global climate model projections
combined with estimates of hydrologic sensitivities, estimated for different seasons and at
different change increments, can provide a basis for approximating cumulative distribution
functions of streamflow changes similar to more common, computationally intensive full-simulation
approaches that force the hydrologic model with downscaled future climate scenarios.
For purposes of assessing risk, we argue that the sensitivity-based approach produces viable first-order
estimates that can be easily applied to newly released climate information to assess
underlying drivers of change and bound, at least approximately, the range of future streamflow
uncertainties for water resource planners.
- Vano, J. A., & Lettenmaier, D. P. (2014). A sensitivity-based approach to evaluating future changes in Colorado River discharge. Climatic Change, 122(4), 621-634. doi:10.1007/s10584-013-1023-x
|Funding Statement (additional comments about funding)
- Support for this work was provided by NOAA's Regional Integrated Science Assessment program, grant number NA10OAR4310218, to Oregon State University's Climate Impacts Research Consortium.