Subsurface flow

Subsurface flow is the movement of water underground as part of the water cycle. When rain or snow falls on land, some of it stays on the surface and forms streams and rivers. But some water seeps into the soil through a process called infiltration. This water travels beneath the Earth's surface, helping to keep the soil moist and filling up underground stores of water called aquifers. The extra water that flows underground is known as subsurface runoff, and scientists study this movement using special equations to understand how groundwater moves.

Runoff

Water moves from places where the water table is higher to places where it is lower. This water can flow on the surface in rivers and streams, or it can travel underground through rocks and soil. How much water reaches the surface or underground depends on many things like rain, how wet the soil is, how easily water can pass through the ground, how much water is already underground, and whether the ground is frozen. The way underground water moves is mostly decided by how much the water level slopes, what kind of ground it is moving through, and any obstacles in its path. The time it takes for this underground water to move can be from many years to hundreds of years. Maps of this movement are made on scales ranging from 1:250,000 to 1:2,000,000.

Surface return

Subsurface water can come back up to the surface in different ways, like from a spring, seep, or water well. It can also flow back into streams, rivers, and oceans. This water returns to the land at a lower place than where it first soaked into the ground, moving because of gravity. Groundwater moves very slowly and can stay underground in places called aquifers for many thousands of years. Eventually, much of this water makes its way to the ocean, where the water cycle starts over again.

Subsurface flow

When rain falls on the land, some water stays on the surface and forms streams and rivers. But some water seeps into the ground. This water moves through the soil underneath us. This movement of water below the surface is called subsurface flow.

Subsurface flow can happen even when the soil isn't fully wet, but it moves faster when certain parts of the soil are soaked with water.