Our honey bees need a reliable source of clean water even though their major source of water comes from nectar. In hot summers a bee colony may need several litres of water per day which they collect from puddles, rivers, lakes, or water troughs which are close to the their hive.
Every colony has worker bees whose main task is collecting water and if necessary foraging worker bees will quit forage and help with water collection. Each water collecting bee usually makes about 50 daily trips, each time collecting about 25 mg of water.
Our bees keep the humidity and temperature in the beehive at an optimal level of 35°C. In hot summers however, temperatures inside the hive would go higher, endangering the colony or even melting the honey combs, if bees would not use evaporative cooling by spreading a thin film of water on top of sealed brood cells or on the rims of cells with larvae or eggs. Worker bees flap their wings quickly and create an airflow inside the hive which evaporates the water and cools the interior of the hive.
Bees also need water to digest and metabolise their food properly. The food for developing bee larvae contains around 70% water and is secreted by hypopharyngeal glands of worker bees using honey, pollen and water.
Adult bees also need water as they eat honey. Raw organic untreated honey that bees store in their honeycomb crystallises naturally after some time due to its glucose content. Because of this concentration of glucose, bees need water to dilute the honey.