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XXI
HYDROLOGICAL YEAR BOOK PUBLICATION
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Introduction
Great Attempt has been made all along to expedite the engineering processing of the stream flow
data to be ready for publication, and to translate the publication plan into implementation. Efforts from various
working units as well as personnel concerned pulled together to drive this work into reality. Publication of
stream flow data has begun since 1966. The first yearbook publication came out as Volume 8 for the 1965
water year. It presents records of stage and discharge of 113 gauging stations in 59 streams.
Definition of terms and abbreviations
Table for converting Metric Units to English Units is on page XXX Terms related to stream flow and
other hydrologic data, as used in this report, are defined as follows:
CMS-day is the volume of water represented by a flow of 1 cubic meter per second for 24 hours. It
is equivalent to 86,400 cubic meters, 0.0864 million cubic meter, or 3,050,784 cubic feet, or 70.07 acre-feet,
and represents a runoff of 86.4 millimeters from 1 square kilometer.
Control designates of feature downstream from the gage that determines the stage-discharge
relation at the gage. This feature may be a natural constriction of the channel, an artificial structure, or a
uniform cross section over a long reach of the channel.
Cubic meter per second (cms.) is the rate of stream discharge expressed in volume per a unit of
time, One cubic meter per second is the rate of discharge representing a volume of 1 cubic meter passing a
given point during 1 second.
Discharge is the volume of water (or more broadly, total fluids), that passes a given point within a
given period of time.
Mean discharge is the arithmetic average of individual daily mean discharge during a specific
period.
Momentary peak discharge is the peak discharge at a particular instant of time, at least once a year.
Drainage area of a stream at a specified location is that area, measured in a horizontal plane,
enclosed by a topographic divide from which direct surface runoff from rainfall would normally drains by
gravity into the stream above the specified point. Figures of drainage area given herein are determined from
Royal Thai Survey Department AMS map with scale of 1 to 50,000, unless otherwise noted. They include all
closed basins, or noncontributing areas, with in the area unless otherwise noted.