What factor contributes most to pool water evaporation?

The factor that contributes most to pool water evaporation is temperature. As temperature increases, the kinetic energy of water molecules also increases. This means that more molecules have the energy needed to overcome the forces holding them in the liquid state and transition to vapor. Higher temperatures typically lead to a significant rise in the rate of evaporation, especially when combined with other factors such as wind speed and humidity.

While humidity plays a role in evaporation—since high humidity means the air is already saturated with moisture, which slows evaporation—temperature remains the primary driver. Water quality can influence evaporation indirectly through temperature (for example, water with a high level of dissolved solids may absorb and retain heat differently), but it is not a direct factor. Wind speed can enhance evaporation by moving moist air away from the water surface, but again, it is the temperature that fundamentally determines the rate of evaporation.