How do I know what scale is appropriate for using the data?

The data that is used as input to the BCM is available at different scales. For example, soils data for this version of the BCM were used at two different spatial scales, with different degrees of accuracy. The San Francisco Bay Area and adjacent watersheds were modeled using soil maps generated at the county level. However, the national scale soils maps were used for the rest of the state, thus the data is not as accurate at a fine spatial scale. This model input is likely the biggest factor in evaluating the minimum spatial scale at which results should be applied. Large scale application of model results (such as regions or large watersheds) is always appropriate. However, if small regions are of interest it is important to evaluate if that region is likely to be homogeneous or not, and if general soil mapping would reflect local conditions. It is always important to remember that these model simulations and estimates of hydrologic conditions are based on input data, soils, geology, and climate, all of which have spatial uncertainty.