About the 2014 Basin Characterization Model Dataset

The Basin Characterization Model (BCM) dataset provides historical and projected climate and hydrology surfaces at a 270 meter resolution. This data has formed the basis for multiple research projects and vulnerability assessments applying climate change projections to conservation decision-making, providing a common base-layer and set of assumptions across these projects. The 2014 CA BCM Dataset is now available-- you can find out how to access it from the Climate Commons catalog record.

There are now two versions of the BCM Dataset and a third one coming soon: See this article listing and comparing them.

What's new in the 2014 Basin Characterization Dataset:

The original BCM for California was based on a southwest US product (Flint and Flint 2007), and refined for the California Energy Commission PIER working group effort. This model relied on 4-km spatial resolution climate data from PRISM, the original southwest US maps of national soils (STATSGO), and a regional snow and potential evapotranspiration calibration (see Flint and Flint 2007). This model had a suite of basins that were used for calibration to calculate basin discharge and compare it to measured streamflow to develop statistics across the state and evaluate relative uncertainties in model performance. Future climate projections used in the hydrologic response to future climates for this version of the model were 4 projections (2 models, GFDL and PCM, and 2 emissions scenarios from CMIP3, A2 and B1) that were bias-corrected to the 4-km PRISM historical climate and applied to the BCM.

The revised modeling for the CA-BCM described in Flint et al. (2013) includes the updated 800-m spatial resolution climate data from PRISM, the county level soils data (SSURGO) for the entire state, and more rigorous snow and PET calibrations for California. This dataset included updates to all the basin calibrations as well. The future climate projections included the original 4 projections that were revised with bias-corrections to the 800-m historical PRISM climate, plus an additional 3 projections from the CMIP3 dataset (IPCC 4th Assessment Report) and 11 projections from the CMIP5 datasets (IPCC 5th Assessment Report). These projections included a range of emissions scenarios and representative concentration pathways. All projections were processed by the BCM to provide hydrologic response to 18 future climates.

Use of the BCM datasets and limitations:

The BCM is developed to calculate relatively unimpaired hydrologic conditions and the available datasets do not consider surface impoundments, urbanization, land surface disturbances such as wildfire or deforestation, diversions or other impairments. These datasets can be used to evaluate strategic choices regarding land use, evaluation of relative landscape resiliency to climate change with implications for wildfire, forest health, pests, species distributions and biodiversity, and invasive species. They can be used to evaluate potential changes to water availability and extremes, including flooding, peak flows, erosion, drought, environmental flows and fisheries and recharge zones. The limitations to the appropriate spatial application can be quite small if the underlying input properties are accurate because the energy load calculations are based on the resolution of the digital elevation model, in this case, 270 m. The variables most closely associated with energy loads (PET, AET, CWD) could potentially be applied at the hillslope scale, given the resolution of SSURGO soils data for most locations. However, it is recommended that most hydrologic applications be considered at no less than the size of planning watersheds (Natural Resources Conservation Service’s California Interagency
Watershed Mapping Committee; CalWater 1999).

The estimate of spatially distributed runoff does not equal basin discharge as measured at a streamgage without post-processing to determine the components of runoff and recharge that contribute to stream channel gains and losses, which must be done using some measured data for a given basin. The resultant parameters corresponding to the gains and losses generally reflect climatic conditions and geologic setting, but at the scale of California have not been determined to a degree that allows for the direct extrapolation of basin discharge to all ungaged basins.

The spatial distribution of runoff and recharge, however, provides relative differences over the region and can indicate the differences in sensitivity of basins to changes in climate. The estimates of changes in soil moisture and CWD do not rely on interpretation of bedrock permeability, and uncertainties correspond more closely with those of the mapped soil properties and climate data. Because the BCM model outputs are calculated on a grid-cell basis, results can be summarized across landscapes using summary units of any size of interest such as watersheds, ecoregions, or political boundaries. The ability to spatially project hydrologic model outputs permits the cross-comparison of these landscape delineations, with mapped outputs of interest to various fields of research.

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