Water Underground

Water Underground Most of the fresh water on the Earth that is not frozen is underground. Dig almost anywhere on the Earth and you will eventually hit water, and the hole will start to fill!

Precipitation Infiltration Water from precipitation trickles into the soil through cracks and spaces. Spaces between rocks and soil are called pores. Porosity is the percentage of open spaces in the rock or soil. The pore size determines how easily the water will sink into the ground.

Underground Layers

Permeable Allows water to easily pass through. Your clothes are permeable, so you get wet when it rains. Sand and gravel will have large pores between the grains, so they are very permeable.

Impermeable Does not allow water to easily pass through. Has few pores or cracks. Will cause water to pool on top of it. Clay and granite are impermeable as are umbrellas!

Saturated Zone When water reaches an impermeable layer, it cannot soak in any deeper. The water will start to fill the spaces above the impermeable layer. This layer that is totally filled with water is called the saturated zone. If you dig a hole this deep you will see your hole start to fill with water. Saturated means to soak or fill completely.

Water Table The top of the saturated zone is called the water table. The more it rains, the higher the water table will get. The more water you take out through a well, the lower the water table will get. Knowing the depth of the water table will tell you how far down you must dig to find water. Where the water table is above ground you will find streams, ponds, and lakes.

Unsaturated Zone The area above the water table is the unsaturated zone. This permeable layer allows the water to infiltrate down to the water table. Also called the Zone of Aeration

Aquifers Underground layer of rock that holds water. Range in size to small underground patches to an area covering several states. Great places to dig wells.

Aquifer Diagram

Bringing Groundwater to the Surface

Springs If the water table is at ground level, water may flow out of the ground. This is called a spring. Usually occur on sides of hills or in low areas.

Water Table Wells A human made hole that extends down past the water table. Well head is above the water table. Water must be pulled or pumped up to be used.

Artesian An artesian aquifer is a confined aquifer containing groundwater that will flow upward through a well, called an artesian well, without the need for pumping. Water may reach the surface if the well head is below the confined water table, this is called a flowing artesian well.

Artesian Wells Work just like an artesian spring. Since the well head is below the water table, water pressure forces the water up out of the well. So you don’t need to pump the water out, it comes to you.

Recharge Aquifers need a constant supply of water to maintain the water table. The water added is the aquifer’s recharge. The surface where the water enters the aquifer is the recharge zone. It may be many miles from the aquifer.

How Homes Get Water Works by gravity. Water from water tower is above your home, so the water flows downhill through pipes to give you water. The higher the source, the more pressure you have.