WSP05233

• File Number: 8029
• Description: Section D General Correspondence - Colorado Agencies ‎(Alpha, not Basin Related)‎
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 10/4/1960
• Author: Colo River Project
• Title: CSU, Colorado Natural Resources - Dr Garnsey - Corres 1959-1962 - Western Resources Conference - Tentative Program
• Water Supply Pro - Doc Type: Report/Study

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With such an approach we can construct a so-called "synthetic hydrology"

for the Colorado River by relatively straightforward sampling methods. For

example, we have used a table of randarn numbers to instruct us which of the

forty years of record to use, and in which order. We mow the random number

table is applicable because of the fit of the normal curve. Thus, we have been

able to generate thousands of years of run-off, silnply from the forty years of

record.

It must be emphasized that these thousands of years of run-off are based

on two crucial assumptions:

1. That the conditions that applied to the river basin from

1929-1959, the years of our sample, are representative of

the conditions of the future; or, in other words, we are

assurn:iJlg a homogeneous and 1lllchanging universe.

2. That the river flows are not sequentially related through time,

but that they are randomly distributed through time.

If these assumptions hold, then we can generate thousands of years of

run-off and use these years to help us decide how to fill the Powell Reservoir,

and how to develop optL~ operating procedures on the river.

Vii th such an approach we are not improving our predictive ability. Vie

are silnply taking the run-ofi's for the past forty years and re-using them, but

in a random fashion. We are not puzzled by which year to start with, and

which year to end with. Moreover, we have many more years to use than just

the forty years. Finally, and most ilnportant, we are then able to make such

statements as the following: 90% of the time, the river flows will average

between x million acre feet and y million acre feet for a 10 year period; or for