TreeFlow - South Boulder Creek near Eldorado Springs, CO

South Boulder Creek near Eldorado Springs, CO

Calibration & Validation

Long-term Reconstruction

Background

The City of Boulder obtains about 80% of its water supply from the Boulder Creek watershed, and return flows from the city are extensively used for agriculture downstream. While the city does not draw water directly from it, South Boulder Creek meets Boulder Creek above the city wastewater treatment plant and thus it is monitored by the city.

The first reconstruction for the South Boulder Creek near Eldorado Springs gage was developed by Connie Woodhouse in 2001. An updated reconstruction was developed in 2005, by Jeff Lukas and Connie Woodhouse, for AMEC Earth & Environmental (formerly Hydrosphere), consultants for the City of Boulder. The calibration period includes the extreme drought year of 2002.

Reference:

Woodhouse, C., and J. Lukas. Streamflow Reconstructions for Boulder Creek, South Boulder Creek, and the Colorado River. Report to City of Boulder and Hydrosphere Resource Consultants, January 2006.

Metadata

Observed Record

Location: South Boulder Creek near Elsorado Springs, CO
USGS Gage: 06729500

Source: AMEC Earth & Environmental, Boulder, CO

Adjustment: "Natural flow" record, extesively adjusted to account for depletions

Observed Flows

Period: 1907-2002

Mean flow:	54 KAF
Median flow:	52 KAF
Minimum:	18 KAF
Maximum:	99 KAF

Reconstructed Flows

Period: 1566-2002

Mean flow:	53 KAF
Median flow:	54 KAF
Minimum:	7 KAF
Maximum:	94 KAF

Calibration & Validation

Methods

A forward stepwise regression procedure was used to calibrate the observed flows with a pool of potential predictors consisting of ~25 tree-ring chronologies from Colorado (both east-slope and west-slope). 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: Van Bibber Update (CO), Pump House (CO), Big Thompson Update (CO), Dillon (CO), Chokecherry Canyon (CO)

Statistic	Calibration	Validation
Explained variance (R2)	0.69
Reduction of Error (RE)		0.65
Standard Error of the Estimate	11,100 AF
Root Mean Square Error (RMSE)		11,361 AF

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

Figure 1. Scatterplot of observed and reconstructed South Boulder Creek annual flow, 1907-2002.

Figure 2. Observed (black) and reconstructed (blue) annual South Boulder Creek annual flow, 1907-2002. The observed mean is illustrated by the dashed line.

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Long-Term Reconstruction

Figure 3. Reconstructed annual flow for South Boulder Creek (1566-2002) 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 South Boulder Creek flow, 1566-2002. 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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