Chapter 3 Lecture Notes- Groundwater

Chapter 3 Lecture Notes- Groundwater - Prof. Jerry W....

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Prof. Jerry W. Kousen ERTH100 Vincennes University Intro to Earth Science Groundwater Groundwater is water that exists in the pore spaces and fractures in rock and sediment beneath the Earth's surface. It originates as rainfall or snow, and then moves through the soil into the groundwater system, where it eventually makes its way back to surface streams, lakes, or oceans. Groundwater makes up about 1% of the water on Earth (most water is in oceans). But, groundwater makes up about 35 times the amount of water in lakes and streams. Groundwater occurs everywhere beneath the Earth's surface, but is usually restricted to depths less that about 750 meters. The volume of groundwater is a equivalent to a 55 meter thick layer spread out over the entire surface of the Earth. The surface below which all rocks are saturated with groundwater is the water table . The Water Table Rain that falls on the surface seeps down through the soil and into a zone called the zone of aeration or unsaturated zone where most of the pore spaces are filled with air. As it penetrates deeper it eventually enters a zone where all pore spaces and fractures are filled with water. This zone is called the saturated zone . The surface below
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
which all openings in the rock are filled with water (the top of the saturated zone) is called the water table . The water table occurs everywhere beneath the Earth's surface. In desert regions it is always present, but rarely intersects the surface. In more humid regions it reaches the surface at streams and lakes, and generally tends to follow surface topography. The depth to the water table may change, however, as the amount of water flowing into and out of the saturated zone changes. During dry seasons, the depth to the water table increases. During wet seasons, the depth to the water table decreases. Movement of Groundwater Groundwater is in constant motion, although the rate at which it moves is generally slower than it would move in a stream because it must pass through the intricate passageways between free space in the rock. First the groundwater moves downward due to the pull of gravity. But it can also move upward because it will flow from higher pressure areas to lower pressure areas, as can be seen by a simple experiment illustrated below. Imagine that we have a "U"-shaped tube filled with water. If we put pressure on one side of the tube, the water level on the other side rises, thus the water moves from high pressure zones to low pressure zones.
Background image of page 2
The same thing happens beneath the surface of the Earth, where pressure is higher beneath the hills and lower beneath the valleys The rate of groundwater flow is controlled by two properties of the rock: porosity and permeability . Porosity
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 10

Chapter 3 Lecture Notes- Groundwater - Prof. Jerry W....

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online