There is much talk about water temperature, mostly the perspective of the user: “Is the water cold?”
Let’s talk about water temperature as an important factor in the aquatic ecosystem. The photo shows the temperature curve of a biological pool in the Alentejo middle of February. Two characteristics are quite evident. The temperature produces a typical curve during the day. These are the oscillations of day and night hours. At sunrise the temperature is at its lowest and at the end of the afternoon it has its maximum. The other feature is the steady rise over the month. The water becomes a little warmer each day and this regardless of the weather.
The rise in the temperature of the water depends less on the sunny days, but much more on the calendar, that is, the days are getting each time a little longer, until the longest day in June. But it is not mainly the temperature of the air that raises the water temperature, it is more the global radiation. And that is relatively independent of the weather. Only on very overcast days or with constant rain, it is noticed that this energy, also coming from the sun, does not have great effects to the “heating” of the water of the biological pool.
This process leads to the phenomenon that in the South of Portugal, Algarve and Alentejo, almost guaranteed, we can count on water temperatures of 20ºC or more already during the month of March. So everything is ready for the debut of the biological pool later this month!