Water Supply and Management
Discussion Objectives
Important Properties of Water
 Distribution of Water
 The Water Cycle
 Major Uses of Water
 Human Impacts on the Water Cycle

Properties of Water

Hydrogen bonding:
Properties of Water

Hydrogen bonding leads to the
important characteristic of high specific
heat.
– Takes a lot of energy to melt or vaporize
water;
– Implications:
• Does not change temperature rapidly;
• Influences climates;
• Organisms can regulate temperature.
Climate Effects Near Large
Bodies of Water
Properties of Water

Water is the “universal solvent”:
– Dissolves some materials rapidly (salts)
and some materials very slowly (granite).
– Major transport mechanism in plants and
animals: nutrients and pollutants.
– Major transport mechanism of Non-Point
Source Pollutants locally and regionally.
Properties of Water
Properties of Water

Water has a high surface tension:
– Implications:
• Facilitates movement through membranes and
vascular tissues;
• Water surface is a habitat to organisms.
Properties of Water

The solid form of water is less dense
that it liquid form.
– Implications:
• Global temperature;
• Ice floats…important characteristic for fish?
Properties of Water

Water is transparent, therefore light can
penetrate the surface and allow
photosynthesis to occur.
– Implications:
• Oligotrophic systems vs. Eutrophic systems
Groundwater and Streams

Groundwater
– Water found below the Earth’s surface, within the zone of
saturation, below the water table
– Water table, recharge zones, discharge zones, aquifer, cone
of depression

Effluent Stream
– A type of stream where flow is maintained during the dry
season by groundwater seepage into the channel

Influent Stream
– A type of stream that is everywhere above the groundwater
table and flows in direct response to precipitation
How Much Water is There?
Approximately 97% of the Earth’s water
is in the oceans.
 About 2% is in the polar ice caps
(freshwater).
 The remaining 1% is freshwater found
in rivers, streams, lakes, groundwater
and atmospheric water vapor.

Global Water Supply
Global Distribution of Water

Is the global distribution of water
uniform?
Water Usage

Do All Nations Use Water the Same?
– Developed nations that have high industrial
and/or agricultural output consume large
quantities of water.
– Global per capita water usage is
approaching 200 gallons/day.
Major Water Use Categories

Off-stream use:
– Uses that temporarily or permanently remove
water from its source (e.g., irrigation or cooling
waters).
– If not returned, it called “consumptive use”.

In-stream use:
 Uses that do not remove water from its
source (e.g., hydroelectric power or
recreation).
 Multiple uses can cause conflict between
users.
In Stream Water Use
Water Use Trends In The U.S.
Water for irrigation and and the
thermoelectric industry have been the
largest water users since the 1950s.
 Water usage for domestic consumption
has increased with the population
increase, but industrial consumption has
decreased.

Water Use Trends in The U.S.
From 1950-1975, water use steadily
increased with the population increase.
 From 1975 to the present, water use
has remained constant although the
population has grown.
 This trend suggests that water
conservation and management
techniques have been mildly successful.

Water Budget for the U.S.
Factors Influencing Water
Distribution

Global Air Flow Patterns:
Factors Influencing Water
Distribution

Local Air Flow Patterns:
Factors Influencing Water
Distribution





Evaporation
Precipitation
Run-off
Infiltration
Percolation
Evaporation
Approximately 66% of total precipitation
is lost through evaporation or
evapotranspiration processes.
 Evaporation and transpiration rates vary
depending on season, vegetation, soils,
land use and local climatic conditions.

Precipitation
Precipitation rates are a function of
relative humidity.
 Approximately 34% of the total
precipitation enters groundwater or
surface water supplies.
 Is this enough to compensate for
current water usage patterns?

Precipitation as a function of
relative humidity:
Mean Annual Precipitation
Water Run-Off

Water stays on the land surface.

Influenced by local topography.
Percolation
Sources of Our Water Supply

Drinking water supplies come from surface
water bodies and groundwater aquifers.
 Approximately 51% of the U.S. population
gets drinking water from underground wells.
 A higher percentage in Southeast Missouri
gets its water from private wells.
 Are these private wells required to be tested
to determine if the water is free of biological
or chemical contamination?
What is an Aquifer?

Aquifer:
– Underground soil or rock formations that
contain pore space or fractures that may
become filled with water.
– Aquifers near the ground surface are called
surficial or unconfined aquifers (any
potential problems with this type?).
– Aquifers separated from surficial aquifers
by an impermeable layer are called
confined aquifers.
Aquifer Recharge and Discharge
Aquifers can be recharged by surface
infiltration and by streams.
 This is a long-term process…takes
years to replace lost water.
 Groundwater moves very slowly.
 Aquifers can recharge surface water
bodies.

Groundwater Overdraft
The total groundwater supply in the U.S.
is large, however, it is unevenly
distributed and withdrawals exceed
recharge in some areas (e.g., Ogallala
Aquifer).
 The excessive removal of groundwater
is called “overdraft”.

Human Impacts on the Water
Cycle

Physical Impacts:
– Deforestation;
– Dams/Flow Diversion/Channelization;
– Creating Impervious Surfaces.
Impacts of Deforestation
Damming of Rivers
Effects of Stream Channelization
Stream channelization is the widening,
deepening, clearing or lining of existing
streams.
 Positive effects:

– Improve drainage;
– Flood control;
– Erosion control;
– Improve navigation.
Effects of Stream Channelization

Environmental effects:
– Alteration of stream habitat;
– Alteration or removal of streamside
vegetation and habitat;
– Removal of water storage capacity in
wetlands;
– Removal of wetlands;
– Loss of aesthetic quality of the stream.
Impervious Surfaces



Increased runoff.
Source of
pollutants.
Reduction in
groundwater
recharge.
Ex. 5 cm rain
¼ acre wood: 6 mm runoff
¼ acre housing project:
18 mm runoff
Overdrawing of Water Supplies
Overdrawing from surface sources
causes a drop in water levels that may
affect habitat and organisms occupying
the reservoir or lake.
 Groundwater:

– Lowering of the water table;
– Land subsidence;
– Saltwater intrusion.
Overdrawing of Groundwater
Overdrawing of Groundwater
Land Subsidence
Land Subsidence
Saltwater Intrusion
Saltwater Intrusion
Sustainable Water Use

Sustainable water use:
– The use of water resources by people that
allows society to develop and grow into an
indefinite future without causing the
degradation of the components of the
water cycle or the ecological systems that
depend on it.
Sustainable Water Use Planning

Sustainable use criteria:
– Sufficient water volume to maintain human
health;
– Sufficient water volume to maintain
ecosystems;
– Maintaining water quality standards;
– Providing for the renewal of water
resources;
– Promoting water-efficient technology and
practice;
– Appropriate pricing of water resources.