Water Beneath the Surface Groundwater Water Beneath the Surface

What is Groundwater? Groundwater is the water that is beneath Earth’s surface. It is a major source of fresh water in the United States.

What is an Aquifer? Aquifer – a body of rock or sediment that stores groundwater and allows the flow of groundwater In order for water to flow freely, pores or fractures must be present and connected to each other

Factors that Affect an Aquifer The ease with which water flows through an aquifer is affected by porosity and permeability. porosity: the percentage of the total volume of a rock or sediment that consists of open spaces. permeability: the ability of a rock or sediment to let fluids pass through its open spaces, or pores

Factors that Affect Porosity Sorting – the amount of uniformity in the size of the rock or sediment particles. well sorted = sediment are all about the same size poorly sorted = sediment contains particles of many sizes loosely packed particles = many open spaces that can store water, so the rock has high porosity tightly packed particles = few open spaces, so has low porosity

Sorting – draw this sketch in notes well sorted well sorted poorly sorted

Factors that Affect Permeability To be permeable, open spaces must be connected The larger and better sorted the particles are, the more permeable the rock or sediment tends to be

Are All Soils Permeable? Water flows well through gravel and sand Water will NOT flow through clay, which is impermeable

Groundwater Zones Water is pulled down through soil and rock layers by gravity until it reaches an impermeable layer. The water then begins to fill or saturate, the spaces in the rock above the impermeable layer. As more water soaks into the ground, the water level rises underground and forms two distinct zones. 1. zone of saturation 2. zone of aeration

Groundwater Zones

What is the Zone of Saturation? The Zone of Saturation is the layer of an aquifer in which the pore spaces are completely filled with water. It is the lower of the two zones of groundwater The upper surface of this layer is called the water table.

What is the Zone of Aeration? The Zone of Aeration is the zone that lies between the water table and the Earth’s surface It is composed of three regions: The uppermost region holds soil moisture The middle layer is dry, except during periods of rain, and thus contains air in its pores The bottom region is the capillary fringe (causes water to be drawn/soaked up from the zone of saturation)

Groundwater Zones

How does Groundwater Flow? Downward Flows downward in response to gravity This rate is dependent on the rock layers (permeability) Horizontally This rate depends on the permeability of the aquifer and the gradient, or steepness, of the water table

How Deep is the Water Table? The depth of the water table depends on: Surface topography The permeability of the aquifer The amount of rainfall The rate at which humans use the water

How Deep is the Water Table? During periods of prolonged rainfall, the water table rises During periods of drought, the water table falls and flattens

Why Should We Conserve Groundwater? In some areas, groundwater is the only source of freshwater Replacement of this water can take hundreds or thousands of years to replenish

What is a Recharge Zone? A recharge zone is anywhere that water from the surface can travel through permeable rock to reach an aquifer

What is a Recharge Zone? Pollution in a recharge zone needs to be avoided or it can contaminate the groundwater supply

How Does Groundwater Reach the Surface? A well is a hole that is dug to below the level of the water table A spring is a natural flow of groundwater to Earth’s surface in places where the ground surface dips below the water table

What is a Hot Spring? Groundwater is heated when it passes through rock that has been heated by magma Groundwater that is at least 37ºC (98ºF) and rises to the surface before cooling produces a hot spring Hot springs that periodically erupt form surface pools or through small vents are called geysers

What is a Hot Spring?

Create flashcards for the following: ASSIGNMENT: Create flashcards for the following: Groundwater Permeability Porosity Infiltration Aquifer Water table Recharge zone