Calibration & Verification

Methods

A forward stepwise regression procedure was used to calibrate the observed flow record with a pool of potential predictors consisting of ~30 tree-ring chronologies from Colorado. The residual chronologies, with the low-order autocorrelation removed, were used. Six predictor chronologies were selected by the stepwise procedure for the reconstruction model for the Colorado River near Kremmling. Validation statistics were computed using a leave-one-out (cross-validation) approach.

Predictor Chronologies: Dillon (CO), Gould Reservoir (CO), Pump House (CO), Montrose (CO), Cochetopa Dome (CO), Princeton Douglas-fir (CO)

(For explanations of these statistics, see this document (PDF), and also the Reconstruction Case Study page.)

Figure 1. Scatter plot of observed and reconstructed Colorado River annual flow, 1916-2002.

Figure 2. Observed (black) and reconstructed (blue) annual Colorado River annual flow, 1916-2002. The observed mean is illustrated by the dashed line.