Check and Maintain Water Level
A lot of water will be lost throughout the swimming season largely because of evaporation and normal wear and tear, such as swimming, splashing and exiting the pool. When you remove debris with your skimmer throughout the week, that's also a good time to check the water level. Ensure it doesn't fall below the level of the skimmer, otherwise the pump could be damaged. If the water is low, use a garden hose to bring it up to safe levels.
If you drain your pool to perform maintenance or once the swimming season has passed, be careful to not let the pool sit empty too long. As a general rule, it's best to leave water in a pool throughout the winter because the weight of the water counteracts with forces from the ground pressing up against the pool from below.