Introduction to GroundwaterUnit Essential Questions:

How does the Earth cycle its water through its major reservoirs? How does society’s use of resources affect water quality?

Presentation Objectives: § Define groundwater and the groundwater profile. § Identify and describe factors that influence the amount of groundwater. § Identify and describe factors that influence the speed of groundwater flow. § Define permeability, aquifer, aquiclude, and confined aquifer. § Explain how a water budget works.

How Much Is There?

• Distribution of Freshwater – More than 90% is in the icecaps and glaciers. – 0.31% is in groundwater – 0.009% is in lakes – 0.0001% is in rivers and streams.

Q1

• The hydrosphere includes all of the water both on and in the Earth. • 71% of the Earth is water!

- Saltwater - Freshwater - Water Vapor

Most useable water!

2.6% of Earth’s Water

What is Groundwater?

• Groundwater is the result of infiltration. – Process by which

precipitation or snow melt seeps into the ground and becomes groundwater.

Groundwater is water that is stored in the pore spaces of ground material.

Q2

• It’s all part of the cycle! – Groundwater flows. – Returns to the surface. – Enters lakes, rivers, or the

ocean.

Ready, Set, Infiltrate!

• Porosity - is the amount of pore space in a material. – Well-sorted soil has a higher porosity than unsorted soil. – Cements of sedimentary rocks reduce porosity.

Which will allow water to infiltrate more?

Soil A Soil B Soil C

The higher the porosity, the greater the infiltration!

Q3

The Groundwater Profile

• Zone of Aeration – Pore spaces are filled with air.

• Capillary fringe – Small amount of water present in the zone of

aeration. • Pulled into small spaces by capillary action.

Q4 The Groundwater Profile

• Water Table – The upper boundary of the zone of saturation.

• Zone of Saturation – Pore spaces are filled with water.

Q4

Groundwater is found in the zone of saturation!

The Water Table• The location of the water table depends

on local conditions.

–Climate and Weather • Higher when it is rainy. • Lower when it is dry.

Q5

–Topography • Water table typically follows

the slope of the land.

By Gosh it Moves!

• The speed of groundwater flow depends on the slope of the water table. – The steeper the water table, the faster its flows!

• The pull of gravity is stronger!

Groundwater flows downhill through the soil!

Q6

– Permeability is the ability of a material to let water pass through.

• A soil with a high permeability has large, connected pores.

–Sand, gravel, limestone, fractured bedrock.

Q7A Place To Flow• The speed of groundwater flow also depends on

the soil’s permeability.

• A soil with a low permeability has tiny, unconnected pores.

–Fine-grained silt, clay, and shale.

The higher the permeability, the faster the groundwater flows!

Real World Application• Landfills are lined with clay at the bottom.

Doesn’t allow toxic chemicals to leak out because its impermeable.

Q8

Where’s the Water?• Groundwater flows in an aquifer.

– Permeable layers where groundwater flows. • Top boundary is the water table. • Water can be extracted using a well. !

• Aquiclude - a layer of impermeable rock that groundwater CANNOT flow through.

• Confined Aquifer – An aquifer sandwiched

between two aquicludes.

Q9

Permeable

Impermeable

Impermeable

Recharge Zone• A confined aquifer has to have an opening to the

surface where water can enter into the permeable layer. • Known as recharge zone.

Q10

Would You Like A Drink?• Most groundwater is retrieved using a well, which

is a hole dug into the ground to reach an aquifer.

• Types of wells – Ordinary well

• Taps into a water table/unconfined aquifer.

– Artesian well • Taps into a confined aquifer.

To access a well’s water we use a pump to draw the water upward rather than let it travel on its normal course.

Q11&12 Under Pressure• The water level in a well is determined by pressure.

• The pressure surface is known as the potentiometric surface. • The water level in a well is where the pressure

line intersects the well.

Q13

Under Pressure• Confined aquifers have higher pressure, so the

water level is higher than a normal aquifer.

• Sometimes the potentiometric surface is above the Earth’s surface. - Known as a flowing artesian well.

- Water flows out all by itself!

Q14 Groundwater Discharge• Groundwater flows until it becomes surface

water. – Often enters into streams, lakes, ponds, swamps or

the ocean.

Q15

• Sometimes, the water table will intersect the land surface and groundwater will naturally flow onto the Earth’s surface.

Groundwater Spring!

Nice and Hot!• Spring water is usually the

average annual temperature for a given location. – New England springs are

about 10°C.

• Hot springs – Temperatures are higher than the human body.

• East - aquifers that go deep into the Earth’s crust. – After the first 20 meters, the temperature increase about

1°C every 40 meters. • West - linked to volcanic activity in the area.

Q16 Yellowstone National Park

Special Hot Springs• Mud pots are hot springs

where the groundwater has dissolved rocks into clay.

• Geysers are hot springs that erupt water to the surface.