The hidden date for this stamp can be found inside the weighing rain gauge.
The growing need for solutions to problems involved in the optimum use of water resources is accented by the Canada Post Office International Hydrological Decade Stamp. Hydrology is defined as a scientific field which covers the entire history of the cycle of water on earth. It refers to the circulation of water from the oceans, through the atmosphere, back to the oceans, or to the land and thence to the oceans by overland or subterranean routes. Included in this science is a study of effects on man and the effects of man's activities on water.
The IHD programme extending from 1965 to 1974 is a cooperative international study sponsored and co-ordinated by UNESCO. Canada is one of 97 member states whose purpose is not only to increase knowledge in the developed countries but to increase the ability of the underdeveloped countries to gain knowledge of their own water resources. A Co-ordinating Council of 21 member countries has as permanent delegations the representatives of the U.S.A., the U.S.S.R., France and England. Remaining member countries serve for two year terms; in this capacity Canada has served for the first two of these two year periods. At the National level Canada's committee consists of 26 senior officers of federal, provincial and university water agencies, supported by a full-time Secretariat, whose efforts are currently concentrated on 185 projects.
A prime objective in the Decade's threefold programme is to improve the ability of nations to evaluate their resources and use them to the best advantage. Canada has frequently been estimated to possess from one-quarter to one-third of the world's fresh water but authoritative circles view this as an unsubstantiated claim. A very recent estimate shows that our nation has approximately one-seventh of the world's fresh water in lakes and about one-tenth of the world's fresh water running through its rivers. Experienced researchers in this field indicate the volume of fresh liquid water in ground-water in Canada is currently unknown, as is the amount of fresh solid water in glaciers.
Although some 90 per cent of our population in habit an area within 200 miles of our southern border, more than one-half of our surface waters flow north and therefore are not immediately usable at demand centres. It is recognized that we have the engineering ability to radically change the natural flow of waters but scientific knowledge does not encompass how best to do this or what the ultimate effects might be. Estimates place the proportion of sea-water as 97 per cent of the world's total. Two-thirds of the remaining 3 per cent is immobilized in polar regions and in glaciers, therefore for his fresh water needs mankind must depend upon the remaining 1 per cent of the world's supply. A significantly increased population cannot for long depend on the availability of sufficient fresh water unless, in the near future, hydrological work of considerable scope and variety is carried out.
The International Hydrological Decade stamp marks the second occasion in 1968 that the Canada Post Office has introduced a newcomer in the field of Canadian stamp design. The chosen rendition was executed by Hungarian born, Canadian by adoption, Prof. Imre von Mosdossy. Versed in widely varied fields of art and design, the artist has to his credit hundreds of stamps chosen for use by postal administrations in many parts of the world. His designs for this project ingeniously incorporates segments, of a symbol adopted by the Canadian National Committee, International Hydrological Decade. Centered in the design is a weighing rain gauge symbolizing instruments used during the 10 year international programme.