WMOD00288 ‎(2)‎

• Title: Twelve Basin Investigation - Volume I
• Prepared For: Bureau of Reclaimation
• Prepared By: Robert D. Elliot, Jack F. Hannaford, Russell W. Chaffer
• Date: 5/15/1973
• Weather Modification - Doc Type: Report

r

1--40

However, detailed investigation indicated that a more sophisticated and intensive ~
hydrologic treatment must be utilized in order to evaluate the full potential incre-/
mental runoff from incremental precipitation as developed in the meteorologic phase
/

of this project.
This section of the report outlines the general approach utilized in analysis,
defines the reasons for using this approach, and describes in detail the techniques
developed and applied in analysis. Section 2 describes results obtained by major
basins and study watersheds. Tabulations supporting described results appear in
Appendix B.
1.3.1 General Approach - Selection of Techni~. Both total precipitation
during the October 1 - April 30 seeding period and the incremental precipitation re-
sulting from weather modification describ.~d in the meteorologic phase, vary with
elevation and location within the massif. As a consequence, it was decided that
massif units s'hould be broken down by elevation zones within the specific study
watersheds and each elevation zone treated independently with respect to its physical
and hydrologic characteristics as well as its estimated incremental precipitation
during each specified season of analysis. Variation in the percentage precipitation
increase with elevation as described along the profile as well as the strong corre-
lation between precipitation and elevation and runoff production and elevation made
this approach desirable in developing a realistic evaluation of incremental runoff.
Selected precipitation index stations representing each massif are utilized to
describe the quantity of precipitation subject to weather modification during each
of the twenty years of analsis. These stations are supplemented with data [rom snow,
courses and streamflow to better define the hydrologic characteristics of the season
within the productive massif areas. AveI~e seasonal i~y~al maps have been used
to describe the areal distribution of individual season precipitation amounts over
elevation zones and massif units.

Precipitation-runoff relationships ~lere developed by massifs and applied sea-.
sonally by elevation zones to incremental precipitation quantities developed in the
meteorologic phase of this proj ecl. Runoff values were accumulated by elevation
zones, by massif units, and finally by study watersheds to represent total additional
water available by seasons from the massif units within study watersheds. Resulting
incremental runoff represents production from massif units within each study water-
shed prior to regulation and incremental consumptive use by man or in some cases
loss of surface flow to ground water. in the lower portions of some watersheds.
Results represent additional supply available within the watershed and therefore may