Bulletin 1.pdf - California Department of Water Resources - State of ...

CHAPTER III. METHODS AND PROCEDURES
The complexity and magnitude of the task of assembling and interpreting
basic data presented in this bulletin justify some explanation of
the procedure followed. In explaining this procedure it has been found
desirable in some instances to indicate the nature and scope of the physical
data available, and in other instances to review historically the technical
approach to solution of the problems involved.
DEFINITIONS
Basin--Total drainage area above the mouth of a stream.
SubbaSin-Total drainage area of any subdivision of a basin.
Stream Group-Two or more minor streams within a drainage
basin, designated either by the name of the principal stream or by reference
to a geographical feature.
Seasonal Precipitation--Total precipitation from July 1st of one
year to June 30th of the following year.
Mean Seasonal Precipitation--Average seasonal precipitation for
the 50-year period from 1897-98 to 1946-47.
Average Seasonal 'Precipitation--Average seasonal precipitation
for a period other than the 50-year period from 1897-98 to 1946-47.
Weighted Mean Seasonal Precipitation-Summation of the products
of means of adjacent isohyets and the areas between them, divided
by the summation of the areas.
Natural Flow-Flow of a stream unaltered by diversions or storage
of its waters, or by importation of water from another drainage basin.
Seasonal Runoff-Total runoff at any station from October 1st of
one year to September 30th of the following year.
Mean Seasonal Runoff-Average seasonal runoff for the 53-year
period from 1894-95 to 1946-47. This is taken to be the long-time mean.
Average Seasonal Rttnoff-Average seasonal runoff for a period
other than the 53-year period frorp. 1894-95 to 1946-47.
Flood Plain--Valley areas subject to periodic inundation by a
stream are collectively termed its flood plain.
LOCATION MAPS
Plate 1, "Map of California," referred to previously, shows location
of physical features and place names. Even greater detail was desirable
for congested portions of the San Francisco Bay and South Coastal
Areas. Accordingly, larger scale maps of those vicinities are included as
Plate 10, "Portion of the San Francisco Bay Area," and Plate 16, "Los
Angeles Coastal Plain of the South Coastal Area." Plate 1 has been
placed inside the back cover of this bulletin for convenience of use, while
Plates 10 and 16 appear in Chapters V and VII, respectively.
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