WSPC04476

• File Number: 8283.200
• Description: Colorado River Basin-Colorado River Computer Models-Colorado River Decision Support System-RAY
• State: CO
• Water Division: 5
• Date: 12/29/1993
• Title: Hydrosphere-Colorado River Model-Technical Overview
• Water Supply Pro - Doc Type: Report/Study

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0021Q2

Hydrosphere's Colorado River Model

December 29, 1993
Page 9

Severe and Sustained Drought Hydrology

A hydrologic trace was developed to study the effects and possible coping mechanisms
during a severe and sustained drought. The trace was developed from the tree-ring
reconstruction of pre-historic annual flows from 1579 to 1600. This period was found to
contain the most severe drought in the over 500 years of tree-ring reconstructed streamflows.
The annual flows in this period were then re-arranged in a descending order, resulting in a
clustering of the extremely low flows about a single point. This configuration then produced
the most severe and sustained drought hydrology. The annual reconstructed flows as arranged
were then disaggregated over time into monthly flows at Lee Ferry, and again disaggregated
over space to the 29 inflow points in the Colorado River Model.

Indexed Sequential Hydrology

Two indexed-sequential traces are available with Hydrosphere's Colorado River Model.
With the indexed sequential method multiple traces are generated by wrapping the first five
years from the beginning of the historical trace to the end. This is repeated until all possible
sequences (16 sequences in a 78-year trace) have been generated. Each sequence differs from
the next only by the fact that the first streamflow year is incremented by five and wrapped to
the end of the sequence. A second indexed-sequential trace which increments by one year
rather than five is also available. These traces are provided for comparisons between CRSM
and Hydrosphere's Colorado River Model.

Hydrosphere Resource Consultants 1002 Walnut Suite 200 Boulder, Colorado 80302