An attempt to measure evaporation from a Class-A pan using naphthalene sublimation


Abstract: Determination of water losses via evaporation from a natural and man-made reservoir is of crucial importance for water budget calculations. However, the problem of evaporation measurement from free water surfaces has not been solved completely. In many applications, Class-A pans are generally used for measuring evaporation from free water surfaces. However, it is impossible to measure the evaporation by a Class-A pan when the air temperature is below freezing point. Therefore, Class-A pans must be removed from measurement stations during winter months. Under these considerations, we aimed to develop a new measurement method in order to overcome the disadvantages arising from measurements using a Class-A pan. For this reason, a relationship between mass losses due to naphthalene sublimation and evaporation from the free water surface has been investigated experimentally. In the experiment, evaporation from the Class-A pan and the sublimation from naphthalene block were measured using a hook-gauge and a precision balance, respectively. The Pearson correlation coefficient between these 2 mass losses is found to be 0.86, which is fairly encouraging for this first attempt.

Keywords: Class-A pan, Evaporation, Naphthalene, Sublimation.

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