New-York tribune., 1903-01-25
MEASUREMENT OF STREAMS
WORK OF INDUSTRIAL VALUE OF GEO
LOGICAL SURVEY.


One of the many useful classes of work con-
Quoted by the United State Geological Survey
is the measurement of such streams as have
any industrial valUe. Wherever water is likely
to be employed for power or irrigation the
amount available is ascertained by that bureau
Such work is not as easy one might suppose
The volume varies greatly from season to sea-
son, and sometimes from year to year Amy cal
culation by the manufacturer or farmer which
does not take this variability into account would
be misleading. Moreover. streams differ among
themselves in straigktness, the character OF
their beds and other particulars Accurate
measurement is still further complicated by the
lack of uniformity in the movement in a given
cross section. What might be true for one point
would not be true for other points TO the right or
left of it, or al a higher or lower level.
The first step in the work is to place gauge
in a permanent position. and employ a suitable
observer to read it every day. The gauge Is
graduated TO feet and tenths- Usually it is up
right 1t may be laid over slanting, however
In that case, the spacing is widened so as 20
give accurate results. Frequently, perhaps IN
the majority of cases, the station is net located
at the most desirable place for getting the
needed information. The photographer is able
TO pay the observer only from 81 to 80 a nonth
for such service, and must therefore pick out d
spot near the man pace OF IeSlutlte- Ci'N y"
servation a day is made, and its result is trans
mitted on a postal card to Washington
The second factor in the photographers com
putation is the velocity Of the at differ
ent heights To ascertain this only occasional
measurements are necessary. These are made
by experts, but with their aid it is possible to
prepare tables showing the total discharge OF
that particular stream for all the different gauge
readings. After such tabulation is effected the
maximum, minimum and mean flow for any
month in the year can be told at a glance.
Velocity is ascertained with a meter lowered
into the water The instrument contains tiny
screw propeller, the number of whose rotations
under the pressure of the fluid is automatically
registered. Many types of meter have been de-
vised The kind which the bureau prefers has
an electric wire leading up TO a buzzer in the
operators pocket There a click or ether audible
sound indicates TO him the speed of the screw
He counts the number of revolutions IoF
some definite period usually fifty seconds, re-
cords il in his notebook and moves along snort
distance to make another observation.
If measurements are made at various depths
along a vertical line, the results VIII not De
equal For this reason photographers have
studied TO find, if possible, a level that Woulu
fairly represent the average velocity 1or any
vertical. in this way they can simplify the
labor. 1t mas been found that such an average
can be secured by taking the speed at depth
of from six-tenths to two-thirds of the way
down from the surface. To obtain a correct ldea
for the whole stream, though, these tests must
he made 1T a number Of places between one
shore and the other No measurement at
single point oan be trusted to be fairly repre-
sentative.
rroperly 10 space the observations with a
meter in making series that extends across
-. liver \ bridge is a great convenience. When
,o s,,cb structure exists other means are utilized
Coz that purpose A stout cable is sometimes
s,,etcrr-s rom one bank to the other at 4 SUI
fcient elevation 10 sustain a box, or car III
which the operator crouches or kneeis. "ith
The aid Of an assistant he can easily pun MN