integrated water resource management groundwater basics

Water Resource Management, Groundwater Basics

Integrated Water Resource Management

Groundwater basics


How wet is our planet?� 70% of the earth’s surface

is covered in water.• The majority of this water is

contained in the oceans as salt water.

• Other sources for water include the polar ice caps, the atmosphere, and groundwater.


How wet is our planet?

� Surprisingly, less than 1% of the earth’s total supply of water is readily suitable for drinking.

� Of this supply of drinking water, 98% of it is found in underground aquifers. • This water source

is called groundwater.


What is groundwater?� Groundwater is water that is

found underground in the cracks and spaces in soil, sand, and rocks.

� Groundwater is stored in—and moves slowly through—geologic formations called aquifers.


Why is groundwater important?

� Groundwater is a source of drinking water for more than 50% of the people in the U.S.

� Agricultural irrigation is the largestuser of groundwater.

� Paper manufacturing, food processing, and other industrial processes also use a large amount of groundwater.


Where is groundwater found?

� Groundwater is available, at least in small amounts, nearly everywhere, though the quantity available varies from one region to another based on geologic materials and other conditions.

� Humans access groundwater with the use of a pump driven water well or windmill.


How does groundwater move?

� Underground, water slowly moves from an aquifer’s recharge areas (areas where water seeps into the aquifer from rain fall, snow melt, etc.) to it’s discharge area (like streams, springs and lakes).

� Groundwater is always moving (this is called groundwater flow) and moves very slowly--only inches per year.

groundwater flow discharge area

evaporation

recharge area

precipitation

condensation

runoff

transpiration

aquifer

water table

infiltration

Hydrologic Cycle


Most available freshwater is groundwater

Oceans97.2%

Atmosphere0.0001%

0.61%(97%)

Streams and Lakes

0.01%(3%)

The Hydrologic Cycle, Quantities


Hydrologic Cycle, Definitions

Fiction: Groundwater is often thought of as an underground river or lake. Only in caves or within lava flows does groundwater occur this way. Instead, groundwater is usually held in porous soil or rock materials, much the same way water is held in a sponge.


Hydrologic Cycle, Unsaturated Zone

Water moves through the unsaturated zone into the saturated zone, where all the interconnected openings between rock particles are filled with water. It is within this saturated zone that the term "groundwater" is correctly applied. Groundwater is held in aquifers.


Groundwater Aquifers

Aquifer is the term given to a rock unit that will yield water in usable quantities to wells or springs. An aquifer can be visualized as a giant underground sponge which holds water and which, under certain conditions, will allow water to move through it.


• Volcanic Processes:– Groundwater controls water

content of magmas– Groundwater injected by

magmas can metamorphose country rocks

– Geysers are an example of volcanic activity interacting with groundwater

Groundwater and volcanoes


Groundwater Movement• It is a common misconception that groundwater is found in

underground rivers, like those that form limestone caverns. In fact, groundwater is more like the water in a sponge, held within the tiny pores of the surrounding aquifer material. Much like the flow of water in a river, however, the flow of groundwater is subject to gravity and is almost always in motion, flowing from areas of higher elevation to areas of lower elevation.

• It is important to note that the rate of groundwater flow, especially in confined systems, is very slow compared to the flow of water on the surface. It is typically in the range of several inches per year to several feet per year.

• For water to move freely through a rock, the pores and/or fractures must be large enough and connected enough so that the friction from the water moving past the rock particle does not impede the flow. The degree of an aquifer's porosity and conductivity is key to the movement of groundwater through an aquifer.


– Permeable pathways are controlled by distributions of geological materials

– Where groundwater is available as a resource is controlled by geology

– Contaminant transport in the subsurface is controlled by geology

Geology controls groundwater flow

Groundwater movement, large scale


Groundwater movement, small scale

Ground water can move through pores or fractures


Groundwater and WellsWhen pumping begins, water begins

to flow towards the well, in contrast to the natural direction of ground water movement. In response, the water level in the well falls below the water table in the surrounding aquifer. As a result, water begins to move from the aquifer into the well.

As pumping continues, the water level in the well continues to decrease until the rate of flow into the well equals the rate of withdrawal from pumping. The movement of water from an aquifer into a well results in the formation of a cone of depression


Typical Groundwater Problem: Well Near a River

Only clean groundwater is pumped out

Both clean groundwater and possibly contaminated river water is pumped out


What causes groundwater

contamination?

� Leaky underground storage tanks

� Poorly constructed landfills and septic systems

� Improperly abandoned mines and wells

� The overuse of fertilizers, pesticides, and road salts

� Runoff from livestock confinement areas

� Careless industrial and manufacturing organizations


What are the effects of groundwater contamination?

� Groundwater contaminated with bacteria, chemicals, pesticides, gasoline or oil can result in serious human health problems.

� Although it is possible to clean up groundwater contamination, it may cost communities several millions of dollarsand can double or triple the cost of water.

� It costs far less to prevent contamination than attempt to clean it up.


How can groundwater contamination be prevented?

� Development of wellhead protection areas.� Public information and education on

groundwater.� Proper use, storage, and disposal of

chemicals.� Monitoring activities.� Land use planning and

implementation programs.


Typical Groundwater Problem: Leaking Storage Tank


Too Much Discharge?

In some areas overwithdrawal can make the ground sink because ground water pressure helps to support the weight of the land. This is called subsidence.


Case Study: Groundwater in Great

Lakes Basin (GLB)


Role of groundwater in Great Lakes (GL)

• Provides recharge to aquifers• Discharges to lakes, tributaries and other surface water

bodies– Direct discharge rates to GL estimated 800-6,700

ft3/sec– Indirect discharge accounts for 25-97% of streamflow

• Transports pollutants• Provides withdrawals for drinking water, agriculture,

livestock, mining, hydroelectric and thermoelectric power generation


Quantity

• Great Lakes Basin contains 1,000 mi3 of ground water (~ 20% of the total water volume of lakes)

• Ground water is the source of drinking water for more than 8 million people in the Basin

• Ground water is estimated to contribute 22-42% of the inflow to the net water supply in the Great Lakes

• Millions of dollars have been spent regulating lake levels by the International Joint Commission (IJC) and US Army Corps of Engineers using models that do not directly account for ground water…


Source: USGS, “Indirect Ground-Water Discharge to the Great Lakes”


Hydrogeology

• Two types of aquifer systems in GLB– Surficial system

• Most widespread in Basin• Composed of high yield glacial deposits• Greatest hydraulic connection with surface waters• Recharges underlying bedrock aquifers

– Bedrock systems• Vary throughout the Basin, USGS documented 10 different aquifers• Some confined, some semi-confined, and some unconfined• Yields vary depending on aquifer, but most industrial withdrawals

come from these systems• Most are recharged by overlying Surficial aquifers or directly from

surface waters at outcrops


Surficial Aquifer System

Source: USGS National Ground Water Atlas


Source:

Great Lakes Atlas

3rd ed.


Groundwater withdrawals


Population


Urbanization


Key Management Questions

• How does ground water influence lake levels?• How do lake levels affect groundwater?

– Regulation – Climate change

• At what point do withdrawals of ground water resources begin to have significant adverse affects in the basin? – Reduced inflow to Lakes– Water quality in wetlands– Locations of watershed boundaries (groundwater divides)


Models as management tools• Surface water routing models are currently used by

USACE (United States Army Corps of Engineers) to manage lake levels

• Groundwater models are used extensively for localized analysis but not over entire GL system

• Constructing a model over entire GL system requires decisions regarding:– Level of geographic and hydrologic detail– Data acquisition and management– Numerical and computational approach– Manner of describing surface/groundwater

interactions


Case Study: Groundwater Overdrafts


Example: Ohio1843: Acton v. Blundell

“English Rule”

The landowner can pump groundwater at any rate even if an adjoining property owner were harmed.

1861: Frazier v. BrownEnglish Rule in Ohio

Groundwater is “…occult and concealed…” and legislation of its use is “…practically impossible.”

1984: Cline v. American AggregatesEnglish Rule overturned in Ohio

Justice Holmes: “Scientific knowledge in the field of hydrology has advanced in the past decade…” so it “…can establish the cause and effect relationship of the tapping of underground water to the existing water level.”


Explanation


Example: Wisconsin

1903: Huber v. MerkelEnglish Rule in Wisconsin

A property owner can pump unlimited amounts of groundwater, even with malicious harm to a neighbor.

1974: Wisconsin v. Michels Pipeline Constructors Inc.English Rule Overturned

Landowners no longer have “an absolute right to use with impunity all water that can be pumped from the subsoil underneath.”


• Water-level changes in the Texas--Oklahoma-High Plains area.

• The Ogallala aquifer --composed of water-bearing sands and gravel that underlie about 400,000 km2.

• Water is being used for irrigation at a rate up to 20 times more than natural recharge by infiltration.

• Water level (water table) in many parts has declined and the resource eventually may be used up.

Ogallala Aquifer

S. Hughes, 2003


Groundwater Overdraft in the Conterminous U.S.

(from Keller, 2000, Figure 10.13a)

S. Hughes, 2003

integrated water resource management groundwater basics

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