Earth’s Role in the Water Cycle Water Underground Earth’s Role in the Water Cycle

Water Underground About 70% of Earth is made up of water! Only about 2.7% of all that water is freshwater – the rest is found in oceans, lakes or bays – but that’s saltwater and not usable

Freshwater Of that freshwater, while MOST is ‘ locked up’ in glaciers and ice caps, there is freshwater that is available to living things and that is found in places like rivers, streams and groundwater: Groundwater: freshwater that is found and stored underground

Groundwater gets into the ground by falling on the ground (via rain, streams, rivers, etc) and then being soaked into the soil – this area is called the Zone of Aeration: Zone of Aeration – Zone underground where soil allows water to flow through it to deeper levels

Then what…? After moving through the Zone of Aeration, water then moves past the Water Table and into the Aquifer Water Table: the top level of the aquifer / zone of saturation Aquifer: a layer of rock that allows water to flow freely

OMG….complicated… Yeah…. The aquifer is also known as the Zone of Saturation Zone of Saturation: the zone underground that is saturated (filled) with water

Wait….water inside ROCKS? Different rocks have different porosity: Porosity: how much of a rock is ‘open space’ (usually between grains or cracks and cavities) This trait helps determine whether a rock is permeable or impermeable

Permeability Permeable: rock that allows water (or any fluid) to move through it with little resistance (ex. Sandstone) Vs. Impermeable: rock that does not allow any water to move through it – stops the flow of water (ex. Granite)

So how do we get this water??? If the water is located in the ground, below the water table, then we need to build a well: Well – a tool used to access water underground; usually a deep hole in which water can be pumped to the surface

Okay….. By using a well, you create a ‘dip’ in the water table where you are pulling out water – this is called the Zone of Depression Zone of Depression: zone around a well where the water level drops because the water is being removed

Let’s Review…..

Try it yourself….