Geology 1001-section 4
Dr. Dutrow
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WATER

 

· WATER - the essence of life; necessary for survival of our species

-it is a CRITICAL resource  

· Reserves are limited:

 

1. they are rapidly decreasing in quality and quantity.

 

2. they are non-renewable

 

3. Will there be sufficient quantities to sustain our future needs?

 

4. Is the quality adequate for uses intended? Is it being used efficiently with a minimum of waste?
e.g. Running water while brushing teeth wastes 5 gallons!

 

· Properties of water

 

1. a unique substance

 

2. it participates in all geologic processes

 

3. Hydrology -

  
DISTRIBUTION OF WATER ON EARTH

1. Water covers ca. 70% of Earth's surface;

 

2. Reservoirs of water (in volumetric %):

Oceans
=
1.35x109 km3
=
97.3%
Glaciers/polar ice
=
2.9x107 km3
=
2.1%
Aquifers
=
8.4x106 km3
=
0.6%
Lakes/rivers
=
2.0x105 km3
=
0.01%
Atmosphere
=
1.3x104 km3
=
0.001%
Biosphere
=
6.0x102 km3
=
0.00004%
 

 

HYDROLOGIC CYCLE

 

1. is a description of the pathways water moves through the various reservoirs

 

2. gravity of Earth insures that, although water may move around the Earth, that it is CONSERVED.

 

3. Solar driven:

 

4. water evaporates efficiently in the tropics, is transported by winds, and condenses to clouds and rain

 

5. Precipitation:

 

- rain soaks into the ground

- or it runs off the surface

 

- Surface Runoff-

 

- The pattern of rainfall relates to the prevailing weather patterns as well as topography

   - Lakes and wetlands are important repositories for runoff

 

- caution to builders wanting to drain wetlands!

  

 

- Of the total precipitation:

(a) 71% falls on unirrigated land

 

(b) 7% is used for agriculture, industrial, cities needs

 

(c) 22% is in streams/rivers.

  

6. Evaporation -

 

(a) oceans are primary source

 

(b) transpiration

 

(c) sublimation

  

7. There is a LIMIT to the amount of freshwater available

 

8. This hydrologic cycling of water makes fresh water a renewable resource (renewed by rain).

 

HOWEVER, because percolation rates are so slow (50,000 yrs!) groundwater is essentially a NON-renewable resource  

9. Projections suggest that by 2000 our needs will required 25-50% more water. US has only 3 times amount!

 

10. Will Louisiana be part of a future water cartel???

 

 

GROUNDWATER
(Details to be given in class)

 

· Water in the ground -

 

1. ca. 1% total water budget

 

2. 1/3 of that water is in glaciers

 

3. 40x the amount of surface water

  

 · > 50% of groundwater is within 750m of surface

 

 · forms as a result of infiltration of precipitation

 

 

· WATER TABLE -

 

 

* Zone of saturation -

 

* Zone of aeration -

   - Water table mimics topography

 

- in dry regions -

 

    

· Aquifer -

 

 

GROUNDWATER MOVEMENT

 

· Groundwater is in motion,

 

· Movement of water depends on:

 

1. POROSITY -

 

2. PERMEABILITY -

  

 

3. Po and Pe highly variable in rocks  

 

· In zone of aeration, soil retains water on clays

 

 

· Percolation -

 

 

· Recharge -

 

 

· Discharge -

 

 

· Velocity of groundwater movement depends on:

 

1. difference in height (h) between two places and the distance (l)

 

 

2. permeability of material,

   3. cross-sectional area (A)

 

4. Discharge (Q) =

   Darcy's Law - derived from experiment  

 

5. Velocities are variable  

 

WATER CARRIERS

· AQUIFER -

 

 

1. Unconfined aquifer-

 

 

2. Confined aquifer-

  

 

 

· AQUICLUDES -

 

 

· ARTESIAN SYSTEM -

 

 

· PERCHED WATER TABLE

 

 

CONSEQUENCES of GROUNDWATER WITHDRAWAL

 

When mining groundwater removes water faster than it recharges:

 

1. the water table is lowered Cone of Depression -

 

 

· Example: Chicago -  

 

2. Land subsidence -

 

 

· Example: Houston -

 

· Example: New Orleans -

 

· Example: Venice -

  

3. Saltwater Intrusion -

 

 

e.g. New Orleans  

 

WATER QUALITY AND GROUNDWATER CONTAMINATION

 

1. Depends on groundwater chemistry;

 

(a) Hard Water -

 

(b) Soft Water -

 

(c) measure TDS; potable water

  

 

2. Ground Water is easily contaminated

 

(a) Sewage Pollution (wells, springs)

 

i.

 

ii.

 

iii. cleansing

  A. mechanical filtration of bacteria

B. oxidizing bacteria

C. destruction of bacteria

  

 

(b) Industrial Waste -

 

(c) Seawater Contamination - coastal areas

 

(d) Toxic Waste

 

i. Toxic leachates from garbage and industrial waste;

ii. dispersed

iii. major problem

iv. La is largest importer of hazardous waste

v. pesticides and herbicides

   (e) Underground Storage of Hazardous Waste   i. Industrial highly toxic and radioactive materials must be disposed of

ii. High level nuclear wastes can remain dangerous

iii. Criterion:

   A. chemical alteration from groundwater

B. physical alteration by earthquakes

C. accidental or purposeful release by humans

   iv. Current site is Yucca Mtn, NV  

 

GEOLOGIC ACTIVITY OF GROUNDWATER

 

Occurs where underlying rocks are susceptible to chemical weathering.

 

· Dissolution -

 

1. important

 

2. carbonates are highly soluble

 

3. leaves little residue

 

 4. relatively fast process

  

· Chemical Cementation

· Chemical Replacement -

 

· Carbonate Caves -

 

 

· Cave Deposits -

 

- form in

 

- key to

 

- Stalactite -

 

- Stalactite

 

- clay and silt

  

· Sinkholes -

 

· Karst topography -

 

 

 

Other items:

 

· Meteoric water -

 

· Hydrothermal water -

 

 

· Where did water originate?

 

 

· Factoid: It takes 120 gallons of water to produce

one egg!

 

 

· CONSERVE!