the water is absorbing sunlight & if a substance absorbs solar energy then that substance will increase in temperature & water is a kind of substance ->  the water will increase in temperature  the water will increase in temperature & temperature is a measure of heat energy ->  the water will increase in heat energy  the water will increase in heat energy & evaporation means a substance changes from a liquid into a gas by increasing heat energy & water is a kind of substance -> the water will evaporate