TreeFlow - Little Popo Agie River near Lander, WY

Upper Missouri Basin

Little Popo Agie River near Lander, WY

Calibration & Validation

Long-term Reconstruction

Background

The Wind River (which then becomes the Bighorn River) supplies water for 80,000 people and 600,000 acres of irrigated agriculture in north-central Wyoming. Much of the Wind River Basin lies within the Wind River Indian Reservation, home of the Northern Arapaho and Eastern Shoshone.

In 2005-2007, Tom Watson, Anthony Barnett, Glenn Tootle, Steve Gray, and colleagues at the University of Wyoming conducted a research effort to collect new chronologies in the Wind River basin and generate streamflow reconstructions for several gages. Their work resulted in three reconstructions of annual (water-year) streamflow, two of which are archived in TreeFlow: the Wind River near Dubois, WY, and the Little Popo Agie River near Lander, WY.

Note: The reconstruction shown below is the PP1/3 model described in Watson et al. (2009).

Reference:

Watson, T. A., F. A. Barnett, S. T. Gray, and G. A. Tootle. 2009. Reconstructed Streamflows for the Headwaters of the Wind River, Wyoming, United States. Journal of the American Water Resources Association 45(1):224-236.

Metadata

Observed Record

Location: Little Popo Agie River near Lander, WY
USGS Gage: 06233000

Source: USGS

Adjustment: No adjustments to gaged flows

Observed Flows

Period: 1946-1999

Mean flow:	51 KAF
Median flow:	48 KAF
Minimum:	19 KAF
Maximum:	102 KAF

Reconstructed Flows

Period: 1560-1999

Mean flow:	49 KAF
Median flow:	50 KAF
Minimum:	2 KAF
Maximum:	89 KAF

Calibration & Validation

Methods

A forward stepwise linear regression procedure was used to calibrate the observed flow record with a pool of potential predictors consisting of tree-ring chronologies from Wyoming, Colorado, Montana, and Utah that were pre-screened for significant (at >99%) relationships with the observed record. The residual chronologies, with the low-order autocorrelation removed, were used. Three 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: Dutch John Mtn. (UT), North Park Update (NPU), Clarks Fork of the Yellowstone (WY)

Statistic	Calibration	Validation
Explained variance (R2)	0.58
Reduction of Error (RE)		0.50
Standard Error of the Estimate	13,247 AF
Root Mean Square Error (RMSE)		14,179 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 Little Popo Agie River annual flow, 1946-1999.

Figure 2. Observed (black) and reconstructed (blue) annual Little Popo Agie River annual flow, 1946-1999. The observed mean is shown by the dashed line.

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Long-Term Reconstruction

Figure 3. Reconstructed annual flow for the Little Popo Agie River (1560-1999) 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 Little Popo Agie River flow, 1560-1999. 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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