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Record 1,  Textual support,  English

Record number: 1, Textual support number: 1 CONT

Normal thermal stratification of a pond, if it is to occur, generally begins in May or early June and ends in September or early October. Ponds can stratify because water attains maximum density at 39°F. It becomes less dense (lighter in weight) both above and below 39°F. Soon after the ice melts in the early spring, the water temperature throughout the pond rises to 32°F. Winds blowing across the pond's surface cause the water to pile up on the downwind side. The water moves downward, across the pond bottom, to the upwind side. The entire pond begins to circulate from top to bottom, maintaining a uniform temperature. As long as winds are strong enough, the pond temperature will remain uniform, even as the pond begins to warm during spring. This is a period known as "spring overturn."  5, record 1, English, - spring%20overturn

Record number: 1, Textual support number: 2 CONT

When surface water reaches 39 degrees in spring, it becomes heavier than the water immediately below it and therefore sinks. The downward movement of surface water forces water in the deeper parts of the lake upward. The resulting circulation of water is called spring turnover. Spring winds also help promote water circulation.  2, record 1, English, - spring%20overturn

Record number: 1, Textual support number: 1 OBS

turnover: A phenomenon usually occurring in spring and fall because of the increase in density of water above and below the temperature of minimum density. In the spring, as the surface of the water warms above the freezing point, the water increases in density, becomes heavier, and tends to sink, producing vertical currents, while in the fall, as the surface water becomes colder and therefore heavier, it also tends to sink. Also see overturning.  6, record 1, English, - spring%20overturn

Record number: 1, Textual support number: 2 OBS

spring overturn: term extracted from the “Glossaire de l’environnement” and reproduced with permission of the Organisation for Economic Co-operation and Development.  7, record 1, English, - spring%20overturn

Record 1,  Textual support,  French

Record number: 1, Textual support number: 1 OBS

renversement printanier; brassage de printemps : termes extraits du «Glossaire de l’environnement» et reproduits avec l’autorisation de l’Organisation de coopération et de développement économiques.  2, record 1, French, - renversement%20printanier

Record 1,  Textual support,  Spanish