TreeFlow - Rio Grande near Del Norte, CO

Rio Grande Basin

Rio Grande near Del Norte, CO

Calibration & Validation

Long-term Reconstruction

Background

The Rio Grande Water Conservation District (RGWCD) works to protect water rights and promote efficient and sustainable water use within the San Luis Valley in south-central Colorado, in the upper portion of the Rio Grande basin. In 2005, after consultation with the RGWCD, Connie Woodhouse developed reconstructions for four gages (on the Rio Grande near Del Norte, Saguache Creek, Alamosa River, and Conejos River) which represent most of the surface water supply for the San Luis Valley. In 2008, Connie generated an updated reconstruction of the Rio Grande at Del Norte in which the calibration extends through 2002, and this updated reconstruction is archived in TreeFlow.

Metadata

Observed Record

Location: Rio Grande near Del Norte, CO
USGS Gage: 08220000

Source: Colorado State Engineer's Office

Adjustment: Very minor adjustments, nearly identical to gage record

Observed Flows

Period: 1890-2002

Mean flow:	651 KAF
Median flow:	652 KAF
Minimum:	164 KAF
Maximum:	1140 KAF

Reconstructed Flows

Period: 1508-2002

Mean flow:	644 KAF
Median flow:	662 KAF
Minimum:	74 KAF
Maximum:	1166 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 15 tree-ring chronologies from Colorado and northern New Mexico. The residual chronologies, with the low-order autocorrelation removed, were used. Four 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: Slickrock (CO), Trail Gulch (CO), Natural Arch (CO), Cathedral Creek (CO)

Statistic	Calibration	Validation
Explained variance (R2)	0.71
Reduction of Error (RE)		0.69
Standard Error of the Estimate	121,640 AF
Root Mean Square Error (RMSE)		123,784 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 Rio Grande annual flow, 1890-2002.

Figure 2. Observed (black) and reconstructed (blue) Rio Grande annual flow, 1890-2002. The observed mean is illustrated by the dashed line.

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Long-Term Reconstruction

Figure 3. Reconstructed annual flow for the Rio Grande (1508-2002) 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 Rio Grande flow, 1508-2002. 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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