The hydrological cycle begins with the evaporation of water from the ocean surface. This moist air rises and begins to cool; the cooling water condenses and forms clouds. Then water from the clouds falls to the Earth as precipitation. The precipitation may infiltrate the ground and be incorporated as ground water and or it may become runoff. Some runoff evaporates from the ground surface and some flows into streams and/or rivers back into the ocean where cycle begins again. Groundwater penetrates the surface and eventually enters back into the streams and rivers or back into the atmosphere through transpiration and again the cycle continues.
Freshwater inflows are flows from rivers to estuaries. It is important to make the distinction between freshwater inflows and instream and outstream flows. Instream flows come primarily through runoff of the land, which flows, into streams and rivers. Outflows are the flows from estuaries to the coastal ocean.