ADDITIONAL WATER SUPPLY FOR PARIS.
NOTWITHSTANDING the precautions taken by the municipal authorities of Paris to purify the water supplied to the citizens of the French capital, the conclusion has been forced upon the.n that a stop must be put to using the Seine water, which, owing to the pollution which it contracts in its course through the suburbs and city, is a vehicle for the spead of typhoid fever. A movement has, therefore, been inaugurated to furnish Parisians with spring water brought from a distance. The Dhuys, the Vanne, and the Avre already furnish a total supplyof 220,000 cubic metres a day. If to this is added the 50,000 cubic metres that the Doing and the Dunain will furnish when their waters have been brought into the city,there will then bean average of 100 litres of good water each day for each inhabitant.
This quantity, however, though large in comparison with the supply of 1864, when Baris received only 1,200 cubic metres of water from Arcueil, of 1866, with the 30,000 cubic metres furnished by the Dhuys, and of 1875. with the 80,000 cubic metres supplied by the Vanne water being brought into town,is not sufficient for the needs of the present time, especially if the Seine source of supply is cut off.
Paris has already taken up the greater part of the country about it without having succeeded in getting togethera sufficient amount. Hygienists assert that the amount of drinking water necessary for a city increases with the population; and they give as a minimum too litres per inhabitant per day in towns of 2,000 to 5,000 persons;i2olitres for over 5,000; 15010200 and more in large cities. Paris, therefore, requires from 600 to 800 litres per day per inhabitant—that is to say, seven or eight times as much as the above mentioned rivers can supply.
But Geneva in Switzerland places 1,000 metres a day at the disposal of i’s citizens, and New York 405, while Paris allows them only 234,including the polluted watersof the Seine and of the Ourcq canal, which may or may not have been allowed to settle in subsidence reservoirs in which animalcule of ail kinds abound.
The French capital, of course, requires water for hygienic and cleansing purposes besides what is needed for domestic and manufacturing consumption, and.as it is impossible to secure any more water in its neighborhood, attention is now being directed to what seems a practicable plan of bringing a supply to Paris from the lake of Geneva. M. Duvillard, who has made the most careful study of the question, thinks that water should be taken on the F’rench shore of the lake in the arrondissement of Thonon, in Haute Savoie, at a depth of forty metres, 400 metres from the shore.
Carried along in pipes over viaducts or under ground, according to the country, this water would cross the Rhone and the Saone, and, after going 539 kilometres and falling 270 metres in altitude, would reach Chatillon at a height of 103 metres, whence it could be distributed to the highest points in Paris.
The point that has drawn so much favorable opinion to Duviliard’s project is that the water of the lake of Geneva, taken 400 metres from the shore and at a depth of forty metres, is absolutely healthy. It is not possible to find a water that is purer, more exempt from germs, or better protected from all possible contamination.
This is the result of the fact that the lake,having no current, is in reality an immense subsidence reservoir. The germs suspended in water have a tendency to go to the bottom by the act of gravity; hence, the greater the tranquility of the lake, the more thorough is the action of this means of purification.
The action of light is combined with that of subsidence and is fully as powerful. The maximum purity of the lake water is reached in summer, when its surface is quiet and acted on by the fullest intensity of the solar rays. At that time its quality is fully equal to that of the best springs.
Geneva uses no other water than that taken from the lake, whose quality is one of the purest known; and Paris can use that water under even better conditions than Geneva. This water, when reaching the city, will, if anything, be purer and more agreeable—more agreeable, because its temperature will remain between five degrees and eight degrees Centigrade, whereas the Geneva water, which is taken at a slight depth, varies from one degree to twenty two degrees Centigrade; purer, since the point at which the water will be taken for Paris will always be protected by its position and depth from defilement by contamination of the surface or stirring up of the bottom.
The total expense of introducing the water of lake Geneva, with a large allowance for unforeseen events, is estimated at $100,000,000; the undertaking is, therefore, quite practicable from that point of view. The working expenses, interest,and reimbursement of the capital in ninety-nine years, would,if the water were distributed gratuitously, amount to eight francs ($t.to) per cent, and inhabitant during the period of too years.