IRRIGATION IN BRITISH COLUMBIA.

BY E. MOHUN, M. CAN. Soc. C. E.

The art of irrigation may claim to have been practised by the oldest branch of that profession which seeks to direct the great sources of power in nature for the use and convenience of man. Its origin is lost in the mists of antiquity, but the skill and knowledge of hydraulic laws possessed by the first civil engineers are attested by the ruins of the gigantic works constructed by them in Egypt and Assyria. In the former we find the artificial Lake Moris, two hundred and twenty-five miles in circumference, according to Herodotus, supposed to have beenconstructed by Amenemhat III. about 2380 B.C., the great Canal Bahr-Yoosup, 350 miles long, constructed under the Pharaohs, and repaired by Saladin, and the Sweet Water Canal attributed to Sesostris about 1400 B.C. In Assyria, Khammuragas, probably about 2000 B.C., is credited with the construction of numerous canals and the embankment of the Tigris.

About 600 B.C. Nebuchadnezzar embanked the Euphrates; cut canals to carry its overflow into the Tigris; excavated a reservoir, forty miles square and thirty-five feet deep (Herodotus) to receive the waters of the former river, while its channel was being lined with brick; and constructed the far-famed Hanging Gardens of Babylon, on a series of arches at least 75 feet high and 400 Greek feet square. It is said that the water for their irrigation was raised from the Euphrates by an Archimedean screw. In China its history appears to be coeval with that of the Chinese Empire. In India in modern times the Imperial Government spent in ten years on irrigation no less a sum than £10,457,702 sterling. Of this amount £5,673,401 was expended in the North West Provinces, including the great works of the Ganges, the Eastern Jumna, the Agra, and the Lower Ganges canals; the area irrigated in the North West Provinces being 1,461,428 acres.

One of the most gigantic of modern irrigation schemes is proposed in Southern Idaho, and includes the construction of two great canals 300 and 280 miles long respectively, for the purpose of irrigating an estimated area of 4,500,000 acres. At the present day irrigation is in systematic use on every continent, and has proved of inestimable value in adding to the food supplies of the population of the globe.

In 1878 the author received instructions to report upon irrigation as

practised in British Columbia for the information of the Dominion Government, and this paper is principally based upon the notes then taken. He would also bespeak the indulgence of the older members, when entering into details with which they are familiar, but to which, it may reasonably be assumed, some of the younger members have not probably devoted much attention. The main objects of the investigation were to ascertain how much water was required for crops, and whether the existing supplies were properly utilized.

THE MINER'S INCH.

As there will be frequent occasion to refer to the Miner's Inch, the standard measure of water both for mining and agriculture, it may be well before proceeding further to define it.

In California, the inch varies in different localities, and it means the amount which will pass through an orifice one inch square in a two inch plank with a certain head; the usual head is six inches above the top of the orifice. As, however, the depth of the orifice is sometimes made two inches, with a head varying from five to eight inches above it, it is obvious that the inch in California is not a fixed quantity in practice, and the writer believes there is no State law regulating it. Mr. Melville Attwood, a well-known mining engineer in San Francisco, informed the author that the inch recognized by the profession generally was 92 lbs. a minute. About sixteen years ago Mr. Amos Bowman, now of the Geological Survey of Canada, then in California, made a practical and admirable suggestion, namely, that an inch of water should mean 100 cubic feet an hour, or 2400 cubic feet a day. Had his suggestion been adopted, the matter would have been much simplified.

In 1878 the Mining Laws of British Columbia permitted the orifice to be ten inches or less in depth, with any head not more than seventeen inches above the bottom of the orifice. A few years later the author brought the matter to the notice of the Provincial Government; the following is now the definition according to the Land Act:

"In measuring water in any ditch or sluice, the following rules shall be observed:

"The water taken into a ditch or sluice shall be measured at the ditch or sluice head. No water shall be taken into a ditch or sluice except in a trough placed horizontally at the place at which the water enters it, and which trough shall be extended two feet beyond the orifice for the discharge of the water. One inch of water, or any multiple of one inch, shall mean half the quantity that will pass through an

orifice two inches high by one or more inches wide, with a constant head of seven inches above the upper side of the orifice."

These dimensions and head were adopted as being as nearly as possible in accordance with the customary measurement. It is believed that this standard has since been adopted by the Dominion Government.

Taking the value of c. at 0.645 (Greenhill & Unwin):2536 cubic feet a day.. one inch = 0.645 √ 29h × 0.01389 × 43200= And for orifice of different depths with other heads the number of inches = Chx 273.4 × a.

The construction of gauges has for a long time occupied the attention of the hydraulic engineers of Northern Italy; and the researches and experiments made by them, for the purpose of establishing a simple self-acting instrument of that description, led to the discovery of the following curious law of hydrodynamics, upon which is based the principle of the gauges used in Piedmont and Lombardy.

"It was ascertained that, in a vase constantly supplied, but divided into two portions by a diaphragm susceptible of being moved vertically, with a discharging orifice on one side of the vase, a constant difference of level existed in the surfaces of the respective portions of the reservoir so long as the water flowed; and that this difference of level was greater in proportion as the opening of the diaphragm was less compared to that of the orifice. And it was also observed that if, by any change in the direction of the supply or the flow, the level were made to alter on either side of the diaphragm, the corresponding variations in the level upon the two sides continued always to be proportional to the respective difference of level first established." (Burnell.)

A sketch of one of these modules is shewn in Plate VII, Figure 1, in which the water is admitted into the regulating chamber A by the movable sluice b. The water is maintained at the proper height in the regulating chamber when discharging through the orifice O, by raising or lowering the sluice b. The chamber A is covered with a ceiling at the exact level of the required head (which is indicated by a gauge) to still the The unit of measurement varies in agitation of the entering water. different localities as follows:Height of

Orifice.

Width of Head above
Orifice. top of Orifice.

Discharge i cubic feet

ft.

ft.

ft.

a second.

0.61655

Canal of Cremona.

1.31816

0.131

0.131

0.722

Sardinian Module.

0.6562

0.6562

0.6562

2.046

Oncia Magistrale

of Milan......... 0.655

In Spain a module giving very good results is in use on the Madrid Canal, Figure 2. Its construction, however, involves a serious loss of level between the canal and the irrigation ditch. This module consists of two chambers, one above the other. To the upper one the water has free access from the canal, in its floor, which is also the roof of the lower chamber; there is a circular sharp-edged orifice in a bronze plate, in which hangs a circular plug of varying diameter suspended from a float. The plug is so shaped that as the water in the upper chamber rises and falls and the float and plug with it, the free passage in the orifice is diminished or enlarged, so that the quantity discharged is uniform, though the head may vary. From the lower chamber the water is discharged through a culvert into the irrigation ditch.

An ingenious method of measurement has been proposed in England. In this module the orifices are in a sliding metal plate, connected by a link to a lever, attached at one end to a float in the regulating chamber, and so proportioned that the plate rises and falls with the float, maintaining the top of the orifice at a uniform depth below the surface of the water. Mr. Appold has also invented a module in which the water passes through a pipe having an enlarged chamber, in which swings a heavy pendulum, so proportioned that the discharging orifice diminishes as the pendulum under increased pressure approaches a horizontal position.

The general rules for irrigating crops, laid down by DeCandolle, are thus briefly enumerated by Dempsey :

1st. That the water should be well ærated; the presence of atmospheric air is good, but that of carbonic acid gas much better; and it is desirable that the water should contain fertilizing matters.

2nd. In the winter there should be little irrigation, because the plants are then dormant, and water is then superabundant. In spring water is usually abundant. In summer it is wanting; and at that time the water should be given in the evening.

3rd. The quantity of the water to be applied should be varied according

a. To the object of the culture:-When for leaves, more water should be given than when for flowers; less water should be given when for grains or fruits.

b. To the depths of the roots:-The application should be more frequent to the plants of which the roots are superficial; less frequent to deeper roots.

c. To the structure of the foliage:-Those which evaporate much (such as plants with large leaves) more frequently than perennial, or plants with thick leaves.

d. To the consistence of the stalks and of the roots:-Roots with fleshy fibres do not thrive if too abundantly watered; at the same time they are injured by dryness. Tuberculous or bulbous plants, or plants with fleshy leaves, can bear a long-continued dryness, and therefore infrequent, yet abundant, watering suits them well.

e. To the stage of vegetation:-It is important to bear in mind. that young germinating plants require light and frequent waterings; those that are in the height of growth abundant waterings; and when the fruit or seed is being matured the waterings should be infrequent.

Those that have been transplanted require abundant watering.

f. To the nature of the soil, according to which the rules must be modified-The lighter the soil the more frequent and plentiful must be the waterings. If it is a compact and clayey soil, less watering will be required.

g. To the state of the atmosphere:-It will be readily conceived that the watering must be more frequent when the temperature is high, the sky clear, and the air dry, and during drought.

Quantities necessary in Europe, Africa and Asia.

In connection with the subject it will be well to consider the quantities estimated to be necessary in different localities, when irrigation on an extensive scale is carried on; and Mr. Burnell gives the following figures:

The first and last of these quantities Mr. Burnell (and probably the reader will agree with him) considers excessive. He also states that the successful cultivation of rice is estimated to require 1440 cubic feet a day; but as rice is an essentially aquatic plant, requiring to be constantly immersed in water during its growth, while it cannot be cultivated with success north of the 46th parallel, its irrigation need not now be taken into consideration.

In that part of the Sahara which is contiguous to the French possessions in North Africa, much has been done in the way of irrigation, during the last few years, by means of artesian wells. Throughout the low-lying portions of the Algerian Sahara, there appears to be