Final answer:
Evaporation is the phase of the hydrologic cycle that requires the input of solar energy. This energy heats water surfaces and causes water to transition into vapor, which then forms clouds.
Step-by-step explanation:
The phase of the hydrologic cycle that requires the input of solar energy is evaporation.
Solar energy is crucial in driving the hydrologic cycle, where 44,000 TW of solar input is focused on the evaporation of water from surfaces such as oceans, lakes, and moist land.
The absorbed solar energy heats the water, causing it to transition into vapor and form clouds. Each gram of water evaporated requires 2,250 Joules of energy from the sun.
This process is fundamental to the water cycle, which continues as the water vapor eventually cools, condenses into clouds, and returns to the Earth's surface as precipitation.
Understanding that nearly half of the energy absorbed at the Earth's surface goes into evaporating water helps explain the energy dynamics within the hydrological cycle.
Despite the immense solar energy involved, currently, only a tiny fraction, about 0.001%, is utilized in the form of hydroelectricity, which capitalizes on the gravitational potential energy of water.
This renewable resource remains largely untapped in its potential to generate electricity.