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Waimdiai] ^ocicty o[ {^m\ (fngiiiici's,

INCORPORATED 1887.

TRANSACTIONS.

^f.B• — This Booicty, as a body, does not hold itself responsible for tlio fails
and opinions stated in any of its publications.

THE DISUIIAHGK OF THE ST. J.AWilENCK lUVKll.

By Prop. C. H. MoLeod, Ma.F<;., M.Can.Soo.C.E.

Head at Toronto Meeting, June i%th, 1836.

The extreme low water of the S t. Lawrence in tiic! autumn of the past
year called especial attention to the variations in tlio discharge of
the river, and it seemed to the writer to bo a matter of no small im-
portance to obtain a mcasuroment of it at the oxceptioniilly low stage
existing in the early part of November.

From inquiry made at tiie time, it was learned that it was not the
business of anyone in Canada to f;auge the St. Lawrence, and that the
only measurement ever made below Montreal was that by Mr. W. J.
Sproule, M.Cau.Soc.C.K., under the dircetion of the Montreal Flood
Commi.ssiou, in 188C. Having in view the intere.-t of a measurement at
this special time, and iis the work happened to fall into line wilh one of
the courses of Survey ing lectures tiion in progress in MeGill College, the
writer induced some of the students of tlie Uuiver.sity to undertake the
work under his dircetion, a.ssisted by I'rol. 0. F}. Smith, M.Can.Soc.C.E.,
and Mr. J. G. Kerry, A.M.Cau.Soe. CIl. 'I'lie Hon. G. A. Drummond
very kindly placed his private yacht al the disposal of the college for the
purpose, and ^Mr. J'rank Kedpatb gave up two days of his valuable
time to take charge of the yacht during the work.

The position elicseii for the gauging i.s situated about forty miles be-
low Montreal, its upper limit being approximately 0.2(10 feet below the
wharf on the north shore of the river, at Lauoraio. This choice was
made not only beeau.se it is the position best suited lor the work with-
in easy reach ol Montreal, but al.«o chiifly for the purpose of conipar-
i.sou with Mr. Sproulc's tturk, I lie position being that in wiiich his
measurements were made.

It waf9 intended that the gauging shoulil be made during the first
week in November, but owing to unavoidable eircunistauces it had to
be postponed, and was not made until the 13th and 14tli of the month,
llelcrcnce to diagram No. 11 will show that the lowest water levels in
1805 occurred on Oct. 28th, Nov. 2nd and 7ih. On the firstday of the
measurement, Nov. 18lh, thi^ water level was seven inches above its
lowest point, and it rose three inches while the work was in progress.

For a mile or more both above and below the gauging area, the river
runs u straight cour.se and has a very uniform cross section. Over this
distance also, the levels wliieti weie taken under the direction of the
Flood (Jommission in 188tJ showed a einistaiit surl'aco slope.

lu order that the measurements iiiight be entirc^ly comparable with
those of Mr. Sproule, similar methods to those employed by him were
adopted. The velocity observations were made on rod floats immersed
to the greatest possible depths. In the reduction of the work, the ob-

Hci'ved vclooitios were corrootod bj refori'ncc lo a vertionl velocity ourvn
obtaiaud tVimi infitxiii'eiiiL'niM witli nn cicctriual uiirn^iit iiiutcr, by Aiiifilcr.
Nuo page — . Tlio rods wcrcoruniforiii seolioii, i.iid woro loadud w''li liad
weiglitH witliin tin cylinders, liiivinj,' tlie same .seolioii iih tlie rods. The
ininicrscd depths of the rods, as will he seen on llic arconipanying plate
No. 10, ranged I'roui ti I'ect to 42J feet. The aver;i(ie velocities were
obtiiined from the tinieH at erofiaing of the two ranges, and were cheeked
by the velocities between the ^tationB along tlje lines, the positions of
which were fixed by box Sfxtiint angles to points on the shore. All
data as to soundings wero, tlirough the kindness of Mr. John Kennedy,
taken iVuni the plans of the Montreal Flood comniinsion.

The plate No. 8 shows the contour lines of the river bottom and
shore lines for the length of 3000 feet, over which the float ob.serva-
tions were made. It shows also the courscH of tlie several floats, with
their observed velocities and the immersed depth of each float. The
plate No. 9 gives similar information for Mr. 8proulc's ineasuremento,
The plate No. 10 shows the average cross sections for the entire length
of 3000 feet. The upper section refers to the work in 1886 and the
lower one to that in 189&. The mean position iind liiteial range of ench
float is also represented on the diagrams. The dotted lines below re-
present the most probable velocity carves resulting from the observa
tions. In both cases the plotted velocity curve is that which results from
the float observations, after applying the .small correction due to depth
of immersion, as compared with the average depth of ihe water along
its path. This method of reduction gives, of course, slightly smaller
values than those arising I'roin the observed velocities, and the dis-
charge as here computed for 1886 is somewhat less thau the ofiiciul
tigures of the Flood (..oinuiission. The area of the cross section in 1886
was 115,298 square tect, and the discharge 311,101 cubic feet per
Second. 'I'he area of the 189,5 cro9S-.section — when the water was one
foot nine inches below oflicial low water— was 105,432 square feet, and
the ilischarge amounted to 216,621 cubic I'ect per second. At the
period of lowest low wali'r in 1895, iu which the water level was, as
nearly as can be r.sceriiaiied, two feet seven inches holow oflieial low
water, or correspoudeil lu a depth of seven feet eleven inches on the
Hats of Like Ht, Feter, and 24'9 feet minimum depth in the navigable
channel of the river, the cross section was reduced about two per cent,
below that of Nov. 13 and 14, 1896. Assuming that the discharge of
the river varies proportionally to the area of the cross section, and taking
as data tha results of the measurements above given, the discharge at the
lowest water stage 'if ISitS amounted to about 196,000 cubic feet per
second .

Keferriug now to the degree of accuracy which should be expected
in work of this kind, the position." of the lines I, ill, VII, VIII, X, XI,
XIV and XV, Plate No. 8, will bo found to accord somewhat closely with
those upon which the 1886 discharge depends. The additional lines
in groups ucai' to some of these aflford an excellent means of estimating
the limits of precision of such measurements. The lines V, VI and vii
were practically iu the same position and the rods were all immersed
to the depth of 42 feet, yet there was a differehje iu the average velo-
cities of two of the rods of 13-lOOths of a foot per second, amounting
to over six per cent, of the whole velocity. The two lines which show
the extreme velocities 2.07 feet per .second and 2.19 feet per second were
ruu within a few minutes of each other and under precisely similar
conditions, on the morning of the second day of the work, with a
strong wind blowing at right angles to their directions, whereas
No. VII was run on the previous day during very calm weather. It is
perhaps worth noting that although about 10 \v:r cent, of the length
of the poles projeeled abjve the water surface, there was no appreci;ible
drift in the lines.

A similar, hut not quite to great cliserepaney occurred in the veloci-
ties of the rods IX and x. There the difference amounted to about 5 per
cent, of the whole.

Tho writer onnnot but cnnfeis tn foine Huiprinu that under cnnditiont
HO Tory I'avouriiblL' to uniform inntioii in tlic wrtical fllaiuunUof wntor,
8U('h great digorcpancics aH thene Hhniild \w found.

po^rrf /^' o/t 0»fiAan aye* f^e re/-
ae*f)*S t^j^ii» //r»c/ are p/offaj
• fAus-

In tho above diagram the vertical velocity curve resulting from tho
measurements by meter at the position marked (A) on the plate 8 Is
exhibited. The velociiirs at the several depiliH nre the averngis of two
independent nieii8urem(ntg extending: over nhout three uiimiies each..
The velocities lit the surface and iit the 4 feet depth are iiifeordnnt,
owini; to their proximity to the yacht. Similarly, the variations in the
two lower positions arise probably from deflieted currents dne to irre-
gularities in tho bottom. The average velocity given by the curve
afirccB very closely with that wliicii would be obtained from a float
passing through thin jiosition. Owing in lack of time it was itn]iOf.'*ible
to obtain more than one set of men.-uri nicnfs, and tliis curve hss been
tiiken as a typical one in the reduction of the work.

Great difficulty has been experienced in this woik in aaeertaining
definitely the elevation of the water, owing to some uncertainty as lo
tho setting of the Sorel gauge and also as to tlie reading on it which
corresponds to low water. The gange^^ shniild of course lie ref'encd to
permanent bench mniks, which havo ihenisclves been istnldished from
an accurate line of levels referred to one d.itiim plane. The bench
marks in connection with the Alontrcal Flood ('i>niuii>!-ion were not in-
tended as permanent points of reference, and some of theni, notably that
at Sorel itself, is unfortunately unreliable. Lines of levels have been
run on both banks of the !^t. Lawrence by ,Mr, St(x-kcl of the Depart-
ment of Public Works, but the autlier is not aware that tho gauges
have been established in connection with these.

Plate No. 11 gives the relative water levels in 188Gand 1895 as
nearly as the writer has been able to obtain them. There is an un-
certainty amounting to about 10 inches.

The great question of the causes which lca<l to so phenomenal a low
water period is one which the author has at present not had time to
discuss. He is, however, glad to state here that it hiis recently been
the subject of a paper by Mr. Stupart, director of the Meteorological
Service, an extract of which referring to the low water period under

consideration may perhaps be quoted ; —

" We can now see why Lake Huron is so decidedly low, it is duo

to Lake Superior having been low for some years until 18!>4, combined
with tho effect of an abnormal deficiency of rainfall from 1887 to 1895,
excepting tlie years 1892 imd 1893. At the beginning of this same
period in 1887, Lake Ontario was high, bnt two years of exceedingly
small rainfall rapidly lowered the level. In 1889 and 1890, the rain-
fall was above average, and temporarily checked the fidl which wotild

liavo rcHulted from the low water in tlio Upper Lakes ; hut in 1891, a
mnrkoJ tlclieiunoy of precipitation Lrnught a very low winter stage.
Two yeiirH, 1892 and 189H, of almvo average rainfall now improved the
level a little, but the defieiency of rainfall in 18!)4 iind 1895, nnd parti-
cularly in the hitter year, in uonjunction with the etVect of a Hniall in-
take of water by the Niagara Kivcr, doubtless produced the iilmost
phcDomonally low Htago of the past year. I believe that these I'lictH are

amply sufficient to explain the present state of afTaiis

In view of these facts it Ih quite uiirea.soniiblo to suppose

that Lake Ontario will, tliis year or oven next year, attain a high stage,
the increase is likely to bo gradual, Lake Superior in, as we have seen
already, high ; this will help to rait^e the level of Huron, which lake
will rise if the rainfall be even up to the average, and then with au im-
proving head of water in that lake, and consequently in Krie, the flow
by the Niagara will improve and assist in raising the level of Ontario ;
but with so many factors to be considered, it is impossible to predict
with any certainty how long it will be before a really high stage is
again reached."

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TRANSACTIONS CAN SOC C t.

VOL X, PLATE 8

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TRANSACTIONS CAN. SOC C I
VOL X PLATt 9 .

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' The • DISCH ARGE' OF THt

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Note. - Official Low IflMw corresponds to a depHf of 27-6" a
A> 10' 6" on ihe flats of Lako Sf- Paftr,

TfUNSACTIOHS CAN. SOC. C. E
VOL. X ., PLATE II .

SCH AKGg ' OF- THE - ST- LAWR ENCE - RiVER

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TRANSACTIONS CAN. SOC. C. t
VOL. X. PLATE 10.

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