hydrogeology lecture 1

93-482:

Hydrogeological Engineering

Summer 2012

2

Hydrogeology

• Hydrogeology

– study of the laws of occurrence and

movement of subterranean water

• Geohydrogeology

• Contaminant Hydrogeology

3

Groundwater Contamination Cases • Walkerton May 2000

• Woburn Case – Civil Action

– Contamination of TCE near W.R. Grace's Cryogenic plant and J.J. Riley's (Beatrice Foods) tannery, MA.

• Pacific Gas and Electric Company, California

– contamination of drinking water with hexavalent chromium, also known as chromium (VI), in the southern Calif. Town of Hinkley

• Amherstburg – Arsenic Contamination

• Ville Mercier in Quebec;

• Highway de-icing salt problem in Nova Scotia;

• industrial effluents in Elmira, Ontario;

• various pesticides in the Prairie provinces;

• industrial contamination in Vancouver, British Columbia

http://en.wikipedia.org/wiki/Hexavalent_chromium



http://en.wikipedia.org/wiki/Hinkley%2C_California

4

Questions to be Addressed?

• What is groundwater?

• Why is it important?

• Where does it come from?

• How does it move?

• How much can we take for water supplies?

• What is its role in transporting contaminants?

5

Objectives

• To impart knowledge on fundamentals of groundwater hydrology, contaminant transport and remediation

• To train students on applying the fundamentals to real world problems

• To equip the students with some of the techniques and tools required for practicing profession in hydrogeology

6

Hydrological Cycle

Todd and Mays (2005)

7

What is Groundwater?

• Subsurface water that occurs beneath the water table in

soils and geologic formations that are fully saturated

• found underground in the spaces between particles of

rock and soil, or in crevices and cracks in rock.

• flows slowly through water bearing formations (aquifers)

at different rates.

• In places where groundwater has dissolved limestone to

form caverns and large openings, its rate of flow can be

relatively fast but this is exceptional

8


Groundwater

9

Why is it important?

Groundwater is a major link in the hydrologic cycle

Areas of interest

1. Fluid Motion

Flow rates, direction and amounts

Important for transport of chemical substances/

contamination studies

2. Storage

Amount of fluid available in pore/fractures to exploit.

Involves porosity and compressibility

Important for water resources evaluation, land subsidence

10

Groundwater Use in Canada

• Almost nine

million (30.3%)

Canadians

depend on

groundwater

http://www.ec.gc.ca/wate

r/en/nature/grdwtr/e_

sixmil.htm

http://www.ec.gc.ca/WATER/images/nature/grdwtr/a5f6e.htm

http://www.ec.gc.ca/water/en/nature/grdwtr/e_sixmil.htm



11

Alfonso Rivera, Chief

Hydrogeologist, 2006

Groundwater Use in Canada

12

World Water Supply - Groundwater

http://www.ec.gc.ca/water/images/nature/grdwtr/a5f7e.htm

13

How Old is Groundwater?

• Residence time varies from as little as days or weeks to

as much as 10,000 or more years

• By comparison, average turnover time of river water is

about two weeks

14

Hydrologic Cycle


15

Hydrologic Cycle

Reference???

16

Published by AAAS W. M. Alley et al., Science 296, 1985 -1990 (2002)

Hydrological Cycle - Water Fluxes

17

Hydrological Cycle


18

Groundwater Hydrology –

Its Connection to Mass Transport

• Groundwater flow transports the solutes

and/or contaminants along with it.

• Mechanisms

– Advection

– Dispersion

19


Local vs Regional Groundwater flow

20

Local vs Regional Groundwater flow


21

Definitions

• Aquifer

– Saturated permeable geologic unit that can

transmit significant quantities of water under

ordinary hydraulic gradients

• Confined Aquifer

• Unconfined Aquifer

• Semi-Confined Aquifer

• Aquitard

• Aquiclude

22

Definitions

• Aquifer

• Aquitard

– Beds of lower permeability in the stratigraphic sequence that contain water but do not yield water to pumping wells

– Generally referred to as low permeability formations overlie major aquifers

– Aquifer and aquitard separation is ambiguous

• Aquiclude

23

Definitions

• Aquifer

• Aquitard

• Aquiclude

– Saturated geologic unit that is incapable of

transmitting significant quantities of water

under ordinary hydraulic gradients

– e.g., Clays

24

Confined-Unconfined Aquifers

25


26


• Unconfined Aquifers –Also water table aquifer

an aquifer in which water table forms the upper

boundary

– Water level – water table

• Confined aquifers – confined between two

aquitards

– Potentiometric surface

– Concept of potentiometric surface is valid in

horizontal flow in horizontal aquifers

27

Aquifers

Todd and Mays, 2005

28

Recharge-Discharge Areas

• Process by which some of the water from rainfall and melting snow seeps into the soil and percolates into the saturated zone

29


Gaining and Losing Streams


Losing Gaining

Streams

30

Basic Material Properties of

Media and Fluid

• Media – Porosity (n), permeability (k) and

compressibility (α)

• Fluid – Density (ρ), dynamic viscosity (μ) and

Compressibility (βw)

• Others are derived….

– Hydraulic Conductivity (K), Specific Storage (Ss);

Transmissivity (T) and Storativity (S) in confined

aquifers; Transmissivity (T) and specific yield (Sy) in

unconfined aquifers etc.

31

Physical Properties and Principles

• Porosity – void volume/total volume

• Effective porosity – amount of

interconnected pore space available for

fluid flow

• Permeability – Ease with which fluid can

move through a porous rock

32


Types of Pore Spaces

33

Todd and Mays, 2005

Porosities of Different Porous Media

34

Particle Sizes of Different Soils

Todd and Mays, 2005

35

Capillary Rise

Todd and Mays, 2005

36

Specific Yields

41

Summary

• Introduction to Hydrogeology

• Aquifer, Aquitard, Aquiclude

• Confined and Unconfined aquifers

• Recharge and discharge areas

• Gaining and Losing streams

• Properties – Porosity, Effective porosity, Permeability

• Specific Yield

hydrogeology lecture 1

Documents