06环境概论第6讲 Water A Fragile Resource

Pressure
Salt water salt H2O Fresh water
Water Conservation
Reducing Agricultural Water Waste Drip or trickle irrigation
Water Conservation
Reducing Water Waste in Industry Reducing Municipal Water Waste
1976
1997
GloWater Resources among Countries Potentially Volatile International Water Situations – Jordan River – Nile River
Water Management
Water Problems in the US
Groundwater
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Aquifer depletion
Water Problems in the US
Groundwater Aquifer depletion - Ogallala Aquifer
Global Water Problems
Water Management
Providing a Sustainable Water Supply Water Diversion Projects
Water Management
Providing a Sustainable Water Supply Desalinization Condenses Two methods: 1) Distillation
The Importance of Water
Largest watersheds
The Importance of Water
Aquifers
Water Use and Resource Problems
Problems fall into 3 categories: Too much Too little Poor quality / contamination (Chap. 22)
The Importance of Water
Properties of Water Composition and polarity
Hydrogen bonding properties
The Importance of Water
Properties of Water Chemical composition of seawater
Global Water Problems
Population Growth and Water Problems India – 8,000 villages have no local water China – water table falling 2-3 m / year Pakistan – lack of water led to riots in 2001 Mexico – water table falling 3.5 m / year in Mexico City
Water Problems in the US
Surface Water
– Examples of problems:
• Mono Lake • The Colorado River Basin
Colorado River bed in San Luis Rio Colorado, Mexico
(movement of seawater into freshwater aquifers in coastal areas because the freshwater is so depleted)
Too Little Water
Saltwater intrusion
Too Little Water
Average annual precipitation
Water Problems in the US
Surface Water
– Most problems in the West and Southwest – Aqueducts transport water from distance sources
1.4 billion lack safe water 2.9 billion lack proper wastewater disposal 80% of human illness results from insufficient water supplies and poor water quality
Water distribution globally is very inequitable In addition, stable runoff (portion of runoff from precipitation that is available throughout the year) varies Stable runoff can be low even if total runoff is very high Drinking Water Problems
Too Much Water
Flood Management
Levees with natural river
Too Much Water
Case-in-Point: The Floods of 1993
Too Little Water
Droughts Overdrawing Surface Waters Aquifer depletion – Causes subsidence (sinking of the land) – Can lead to saltwater intrusion
Simplified process: Pure water is collected Salt water Produces steam Water boiled
Water Management
Providing a Sustainable Water Supply Desalinization Two methods: Salt impermeable 1) Distillation membrane 2) Reverse osmosis
Providing a Sustainable Water Supply Sustainable water use seeks to provide water to future generations without damaging ecosystems.
Water Management
Providing a Sustainable Water Supply Dams and Reservoirs Pros – Ensure year-round water supply Hydropower Recreation Flood control
Salinization of Irrigated Soil
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–
The gradual accumulation of salt in a soil, often as a result of improper irrigation methods. Occurs most frequently in arid and semiarid lands. As the water quickly evaporates away, it leaves the salt dissolved in it behind.
Too Much Water
Removing vegetation and constructing buildings increases flooding potential on flood plains
Too Much Water
Flood Management
Channelization
Our Supply of Fresh Water
Aquifers—underground caverns and porous layers
of rock in which groundwater is stored – Unconfined aquifers—layers of rock above are porous and allow surface water directly above them to seep downward, replenishing the aquifer contents – Confined aquifers—groundwater storage area between impermeable layers of rock (aka artesian aquifer) Water table—uppermost level of an unconfined aquifer, below which the ground is saturated with water
环境概论 Introduction to Environment
第6讲 Water: A Fragile Resource
Water: A Fragile Resource
英语成语：Crossing The Lubikon
The Importance of Water
Water:
shapes continents moderates our climate is essential for all living organisms
surface in streams and rivers, lakes, ponds, reservoirs, and wetlands Runoff—movement of freshwater from precipitation and snowmelt to rivers, lakes, wetlands, and ultimately, the ocean Drainage basin—the area of land that is drained by a single river Watershed—area of land drained by a river and all its tributaries (entire river system) Groundwater—supply of fresh water under the Earth’s surface