Final answer:
Surface runoff comes from snowmelt and other forms of precipitation like rain. If precipitation does not evaporate or is not absorbed by the soil as groundwater, it can turn into runoff, contributing to rivers, streams, and lakes that flow to the oceans.
Step-by-step explanation:
Water that can flow across the surface as runoff comes from snowmelt and precipitation, such as rain. After water from rain or melting snow reaches the Earth's surface, it can follow different paths. Some of it may evaporate back into the atmosphere, a process often intensified if it encounters vegetation, as some amount of water will immediately evaporate from plant surfaces, a phenomenon that, together with transpiration (the evaporation of water from plant leaves), is known as evapotranspiration.
Water that doesn't evaporate or isn't used by plants may percolate into the soil, becoming groundwater. Groundwater can move through the soil and rock layers of the Earth, sometimes seeping out at springs or flowing into bodies of water like lakes and oceans, or be stored in underground aquifers.
Conversely, when soil is saturated and cannot absorb more water, excess water becomes surface runoff, which is the flow of fresh water over land. This runoff can make its way through streams, rivers, and lakes to the oceans, replenishing these bodies of water.