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TEMPERATURE OF THE WATER.
Perhaps the only data with regard to the water temperatures that have a bearing on the question at issue, is the difference found in the narrows when the temperature after the flood stream from the direction of the sea has run its course, is compared with that after the ebb running from the lake above.
On the surface, temperatures were 4° to 6° warmer after the ebb stream than after the flood stream.
At 18 fathoms similarly the difference was 1° to 3°.
The notes of temperature found are given in the appendix along with the details regarding densities.
Duration of rise and fall of the Tide at Rigolet.—In river estuaries the tide takes a longer time to fall than it does to rise for the simple reason that during the period of rise the water of the river has been held back or the current even reversed, and consequently the river water of both tidal periods has to flow out perhaps entirely during the fall of the tide, which is thus prolonged.
This feature, common to all estuaries, is characteristic of this river, as shown by the tidal record obtained from the gauge placed at Rigolet. On the average for the lunar month, the period of rise of tide was 5 hours 56 minutes and of fall 6 hours 29 minutes.
The rate of progress of the Undulation in the Estuary.—The nature of the progress and recession of the tide as indicated by the times of high water and low water at Indian Harbour, Ticoralak Island and Rigolet is also note worthy. (Appendix “ d ” first part.)
The summit of the tidal undulation progresses from Indian Harbour to Ticoralak Island, a distance of forty miles, in 17 minutes, while to Rigolet it takes 47 minutes ; or 30 minutes additional for the upper eleven miles. This is in accord with the behaviour of the tide in estuaries, although the retardation is greater than is usually the case.
The trough of the tidal undulation progresses from Indian Harbour to Ticoralak Island in 21 minutes, and to Rigolet in 61 minutes, or 40 minutes additional for the upper eleven miles. This retardation is also greater than in ordinary estuaries. The point of importance is that the time of low water is delayed relatively to the time of high water, which corresponds with the shorter period of rise and longer fall which the figures above clearly indicate. This feature is well exemplified on the St. Lawrence, and it is a characteristic which is common to all estuaries.
AMPLITUDE OF THE TIDAL UNDULATION.
Very little change occurs in the amplitude of the tide up to Ticoralak Island, but between there and Rigolet it drops off to 78% of what it is at Indian Harbour, as the best mean value that could be deduced from the observations obtained. Such a change may take place in the upper part of the estuary where the tidal undulation in its progress up the river is reduced in range by the river slope, but this explanation would be only partial. As the
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tide rises at Rigolet, the water flows off into the areas of Double Mer and Lake Melville, which prevents it from rising so high as it otherwise would. Also during the fall of the tide, the immense volume of water flowing out of the expanse above, tends to prevent the tide from falling as low as it otherwise would, which has a further effect in decreasing the range.
The usual behaviour of the tide in estuaries is to increase its rise so long as the shores are converging, and to attain greatest proportions at the true head of the estuary where the river begins. In Hamilton Inlet the shores converge towards Turner Headland on one side, and Ticoralak Point or island on the other, and the tide here has its greatest amplitude. To be more explicit, the tides of most amplitude, i.e., perigee spring tides, are greater than at Indian Harbour ; mean spring tides are equal or slightly greater, while neap tides are nearly 10% less. This may therefore be considered a crucial point representing the head of the estuary for the tide here reaches a maximum in amplitude, notwithstanding the adverse conditions against its rising as already explained in the last paragraph.
In the great expanse of Lake Melville the amplitude of the tidal undulation is reduced to a small amount as might be expected. A table showing the change that takes place in this respect from Indian Harbour to the far end of the lake is given in the appendix. (Appendix “ d ” second part.)
A COMPARISON WITH THE ST. LAWRENCE RIVER.
To draw an analogy with the St. Lawrence river and its mouth, the locality of Turner Headland and Ticoralak Point, described as “ crucial ” may be compared with the region at the lower end of Orleand Island where the tide reaches its maximum rise, and where the river may be properly considered to begin.
Continuing the comparison, the following points of similarity and other-wise may be noted. A diagram to assist in following the purports of the statements is included in the appendix as sheet “ e.”
In the St. Lawrence the tide reverses the current regularly up to Cape Roche and sometimes up to Batiscan, within 25 miles of, but never up to Lake St. Peter the undulation however, does reach the lake causing a variation in level roughly from one quarter to half a foot when the river is not in its freshet stage. In the case of the waterway to Lake Melville, the tide reverses the current all the way, and it flows quite strongly back into the lake, where there is a continuous and regular undulation.
OTHER INFORMATION.
Enquiries were made with regard to the fishing of cod-fish and it was learned that occasionally, and late in the fall only, they were caught in the vicinity of Double Mer Point, presumably for food supply, and not as an industry. The strength of the current makes fishing difficult, and it is not customary to make the attempt. Thus, one party said that three years ago
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cod-fish were caught here, and another said that none to his knowledge had been caught in the last five years.
A fisherman who had spent the last eleven seasons on the Labrador coast, said the farthest up the Inlet that he had known cod-traps to be set was at Black Island on the north side and at Turners Bight on the opposite shore. These places are twenty-five and thirteen miles respectively, below Rigolet.
No boundary line between the waters of the sea fishery, and of the inland fishery, in this locality was known to anybody so far as I could find out.
The foregoing facts regarding the nature of the tidal flow, and character of the water in Hamilton Inlet and Lake Melville and the connecting river, are the results of the work of the Tidal and Current Survey party during the season of 1923. In 1921 data was also obtained by the Hydrographic Survey and this is included partially in the appendix, where the information supplements the greater detail obtained in 1923.
Respectfully submitted,
H. W. Jones,
(B.Sc. : M.E.I.C.)
Senior Tidal and Current Surveyor.
2nd November, 1923.
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