TreeFlow - Big Thompson River at Mouth of Canyon, CO

Big Thompson River at Mouth of Canyon, CO

Calibration & Validation

Long-term Reconstruction

Background

The Big Thompson River is a key component of the Colorado-Big Thompson project, operated by the Northern Colorado Water Conservancy District ("Northern"). In 2002, Connie Woodhouse developed a tree-ring reconstruction of this gage and several others in Northern's east slope supply, and then in 2004, Woodhouse updated the Big Thompson reconstruction using more recently collected chronologies. The updated reconstruction is shown here. This reconstruction was used in analyses for Woodhouse and Lukas (2006).

Reference:

Woodhouse, C.A. and J.J. Lukas. 2006. Multi-century tree-ring reconstructions of Colorado streamflow for water resource planning. Climatic Change 78: 293-315.

Metadata

Observed Record

Location: Big Thompson River at Mouth of Canyon, CO
USGS Gage: 06738000

Source: Northern Colorado Water Conservancy District

Adjustment: "Undepleted flow" record, extesively adjusted to account for augmentations and depletions

Observed Flows

Period: 1947-1999

Mean flow:	128 KAF
Median flow:	125 KAF
Minimum:	30 KAF
Maximum:	234 KAF

Reconstructed Flows

Period: 1569-1999

Mean flow:	123 KAF
Median flow:	125 KAF
Minimum:	29 KAF
Maximum:	217 KAF

Calibration & Validation

Methods

A forward stepwise regression procedure was used to calibrate the observed flow record with a pool of potential predictors consisting of tree-ring chronologies from Colorado (both east-slope and west-slope). The residual chronologies, with the low-order autocorrelation removed, were used. Six predictor 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: Owl Canyon Update (CO), Escalante Forks Update (CO), Dillon (CO), Big Thompson Update (CO), Cochetopa Dome (CO), Sargents (CO)

Statistic	Calibration	Validation
Explained variance (R2)	0.72
Reduction of Error (RE)		0.65
Standard Error of the Estimate	23,489 AF
Root Mean Square Error (RMSE)		24,604 AF

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

Figure 1. Scatterplot of observed and reconstructed Big Thompson River annual flow, 1947-1999.

Figure 2. Observed (black) and reconstructed (blue) annual Big Thompson River annual flow, 1947-1999. The observed mean is illustrated by the dashed line.

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Long-Term Reconstruction

Figure 3. Reconstructed annual flow for the Big Thompson River (1569-1999) 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 Big Thomspon River flow, 1569-1999. 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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