TreeFlow - Arkansas River at Canon City, CO

Arkansas River at Canon City, CO

Calibration & Validation

Long-term Reconstruction

Background

Aurora Water uses the Arkansas River at Canon City gage to represent contributions from the Arkansas Basin to its water supply. In 2004, Connie Woodhouse developed this reconstruction of the Arkansas River at the request of AMEC Earth & Environmental (formerly Hydrosphere), consultants for Aurora Water. Because the model was calibrated prior to the updating of a key chronology (Van Bibber) that ends in 1987, the reconstruction only extends through 1987. Given the chronologies currently available, this reconstruction could be re-calibrated and extended through 2002.

Metadata

Observed Record

Location: Arkansas River at Canon City, CO
USGS Gage: 07096000

Source: AMEC Earth & Environmental, Boulder, CO

Adjustment: Natural flow record, with extensive adjustments for depletions, diversions, augmentations

Observed Flows

Period: 1896-1987

Mean flow:	490 KAF
Median flow:	487 KAF
Minimum:	149 KAF
Maximum:	837 KAF

Reconstructed Flows

Period: 1685-1987

Mean flow:	489 KAF
Median flow:	492 KAF
Minimum:	115 KAF
Maximum:	738 KAF

Calibration & Validation

Methods

A forward stepwise regression procedure was then used to calibrate the observed flow record with a pool of potential predictors consisting of tree-ring chronologies from Colorado. Five chronologies were selected by the stepwise procedure for the reconstruction model. Validation statistics were computed using a leave-one-out (cross-validation) approach.

Predictor Chronologies: Pump House (CO), Cathedral Creek (CO), Van Bibber (CO), Sargents (CO), Jefferson County (CO)

Statistic	Calibration	Validation
Explained variance (R2)	0.63
Reduction of Error (RE)		0.58
Standard Error of the Estimate	88,196 AF
Root Mean Square Error (RMSE)		90,799 AF

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

Figure 1. Scatter plot of observed and reconstructed Arkansas River annual flow, 1896-1987.

Figure 2. Observed (gray) and reconstructed (blue) Arkansas River annual flow, 1896-1987. The observed mean is illustrated by the dashed line.

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Long-Term Reconstruction

Figure 3. Reconstructed annual flow for the Arkansas River (1685-1987) is shown in blue. Observed flow is shown in gray and the long-term reconstructed mean is shown by the dashed line.

Figure 4. The 10-year running mean (plotted on final year) of reconstructed Arkansas River flow, 1685-1987. Reconstructed values are shown in blue and observed values are shown in gray. The long-term reconstructed mean is shown by the dashed line.

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