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Evaporation from lakes and reservoirs in the semiarid region of the Canadian prairies amounts to between two and three times the amount of precipitation and may exceed 40 inches (1.0 m) annually. Because this constitutes a significant portion of the water budget it is important that estimates of evaporation be as accurate as possible, both from an engineering and from an agronomic stand point. All methods of measuring or estimating evaporation have some limitations. Water budget techniques are laborious and may be unsatisfactory because of the problem of accurately determining input data. Evaporation pan conversion methods, with careful on-site correlation of evaporation and certain climatic variables, are fairly satisfactory but their widespread application requires an extensive network of evaporation pan installations (10). The energy budget and mass transfer equations are fundamentally sound but require either elaborate instrumentation or a backlog of meteorological data that are not available on a wide spread network basis. Even the Meyer equation (8), one of the simpler methods of estimating evaporation, requires water temperature data as an input parameter. Water temperature provides, in effect, an integration of the energy balance indices of a specific lake. The biggest problem in applying the Meyer equation is the paucity of water temperature data for Canadian lakes, and small inaccuracies in the estimate of water temperature cause large errors in calculated evaporation.
air-water temperature relations of small shallow prairie reservoirs
Hobbs, E.H. 1972. AIR-WATER TEMPERATURE RELATIONS OF SMALL SHALLOW PRAIRIE RESERVOIRS. Canadian Agricultural Engineering 14(2):75-78.
75 - 78