St. Vrain River at Lyons, CO

The St. Vrain River is augmented by water from the Colorado-Big Thompson project, operated by the Northern Colorado Water Conservancy District ("Northern"). The City of Longmont is the primary municipal user of water from the St. Vrain. 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 St. Vrain reconstruction using more recently collected chronologies. The updated reconstruction is shown here. This reconstruction was used for the analyses in Woodhouse and Lukas (2006).


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.

Calibration & Validation 


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. 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.

Predictors: Pump House (CO), Deer Mountain Update (CO), Big Thompson Update (CO), Hot Sulphur Springs (CO)


Statistic Calibration Validation
Explained variance (R2) 0.65  
Reduction of Error (RE)   0.61
Standard Error of the Estimate 23,419 AF  
Root Mean Square Error (RMSE)   24,259 AF

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


Figure 1.  Scatterplot of observed and reconstructed St. Vrain River annual flow, 1896-1999.

Figure 2. Observed (black) and reconstructed (blue) annual St. Vrain River annual flow, 1896-1999. The observed mean is illustrated by the dashed line.

Long-Term Reconstruction 

Figure 3. Reconstructed annual flow for the St. Vrain River (1571-1999) 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 St. Vrain River flow, 1571-1999. Reconstructed values are shown in blue and observed values are shown in gray. The long-term reconstructed mean is shown by the dashed line.