Figure 21.1 The hydrologic cycle. The movement of water is driven by the energy of the Sun, which causes evaporation from soil and water bodies, and evapotranspiration from plants. Evaporated water condenses into clouds that eventually return the water to Earth as precipitation. Water from precipitation either runs off on the surface or infiltrates the soil. Runoff flows along the surface of the ground until it enters streams and rivers. Water in the soil is taken up by plants or enters the groundwater. Ultimately, excess water returns to the ocean.