Chapter 13: Water Resources
Will We Have Enough Usable Water?
Most of the Earth’s Freshwater Is Not Available to the Us
Freshwater availability
0.024%--Groundwater, lakes, rivers, streams
Hydrologic cycle: Movement of water in the seas, land, and air. It is driven by solar energy and gravity
Groundwater and Surface Water Critical Resources
Zone of saturation: Spaces in soil are filled with water
Water table: Top of the zone of saturation
Aquifers: Naturally recharge, lateral recharge
Surface Run-off: Precipitation that does not infiltrate the ground or evaporate
Water Shed: The region from which water drains into a body of water
Groundwater: Precipitation that infiltrates the ground and percolates downwards through voids in soil and rocks
Water Footprints
Water footprint: Volume of water we directly and indirectly
The average American uses 260 L per day
Flushing toilets, 27%
Washing clothes, 22%
Taking showers, 17%
Running faucets, 16%
Wasted from leaks, 14%
World’s poorest use 19 liters per day
Causes of Water Shortages
Dry climates
Drought
Too many people using a normal supply of water
Wasteful use of water
30% Earth’s land area experiences severe drought
Will rise to 45% by 2059 from climate change
Potential conflicts/wars over water
Refugees from arid lands
Increased mortality
Is Extracting Groundwater the Answer?
Groundwater Depletion: Worldwide Problem
India, China, and the United States: Three largest grain producers. Overpumping aquifers for the irrigation of crops
India and China
Small farmers drilling tubewells. Effect on the water table
Saudi Arabia
Aquifer depletion and irrigation
Aquifers
Unconfined Aquifer: Aquifer with water table as top
Confined Aquifer: Bounded above and below by semi-permeable beds of rock and clay
Limits future food production
Bigger gap between the rich and the poor
Land subsidence
Mexico City
San Joaquin Valley in California
Groundwater overdrafts near coastal regions
Contamination of groundwater with saltwater
Groundwater Depletion
Prevention
Waste less water
Subsidize water conservation
Limit the number of wells
Do not grow water-intensive crops in dry areas
Control
Raise the price of water to discourage waste
Tax water pumped from wells near surface waters
Set and enforce minimum stream flow levels
Divert surface water in wet years to recharge aquifers
Is Building More Dams the Answer?
Large Dams and Reservoirs
Dams/Reservoirs: They capture and store runoff as well as they release runoff as needed to control:
Floods
Generate electricity
Supply irrigation water
Recreation (reservoirs)
Advantages
Increase the reliable runoff available
Reduce flooding
Grow crops in arid regions
Disadvantages
Displaces people
Flooded regions
Impaired ecological services of rivers
Loss of plant and animal species
Fill up with sediment
This can cause other streams and lakes to dry up
Is Transferring Water from One Place to Another the Answer?
California Transfers Water from Water-Rich Areas to Water-Poor Areas
Water is transferred from north to south by
Tunnels
Aqueducts
Underground pipes
California Water Project: Inefficient water use. Environmental damage to the Sacramento River and San Francisco Bay
Is Converting Salty Seawater to Freshwater the Answer?
Desalination
Desalination: Removing dissolved salts
Distillation: evaporate water, leaving salts behind
Reverse osmosis, microfiltration: use high pressure to remove salts
Removing Salt from Seawater Environmental Costs
Problems
High cost and energy footprint
Keeps down algal growth and kills many marine organisms
Large quantity of brine wastes
How Can We Use Water More Sustainably?
Reducing Water Waste Has Many Benefits
One-half to two-thirds of water is wasted
Subsidies mask the true cost of water
Water conservation
Improves irrigation efficiency
Improves collection efficiency
Uses less in homes and businesses
We Can Cut Water Waste in Irrigation
Flood irrigation
Wasteful
Center pivot, low-pressure sprinkler
Low-energy, precision application sprinklers
Drip or trickle irrigation, micro irrigation
Costly; less water waste
Solutions: Sustainable Water Use
Waste less water and subsidize water conservation
Do not deplete aquifers
Preserve water quality
Protect forests, wetlands, mountain glaciers, watersheds, and other natural systems that store and release water
Raise water prices
Slow population growth
How Can We Reduce the Threat of Flooding?
Flood Plains: Too Much Water
Flood plains: Highly productive wetlands, that provide natural flood and erosion control, maintain high water quality, and recharge groundwater
Benefits of floodplains
Fertile soils
Nearby rivers for use and recreation
Flatlands for urbanization and farming
Human Activities Make Floods Worse
Removal of water-absorbing vegetation
Draining wetlands and building on them
Rising sea levels from global warming mean more coastal flooding
We Can Reduce Flood Risks
Rely more on nature’s systems
Wetlands
Natural vegetation in watersheds
Rely less on engineering devices
Dams
Levees
Channelized streams
Reducing Flood Damage
Prevention
Preserve forests in watersheds
Preserve and restore wetlands in floodplains
Tax development on floodplains
Use floodplains primarily for recharging aquifers, sustainable agriculture, and forestry
Control
Straighten and deepen streams (channelization)
Build levees or floodplains along streams
Build dams
Chapter 13: Water Resources
Will We Have Enough Usable Water?
Most of the Earth’s Freshwater Is Not Available to the Us
Freshwater availability
0.024%--Groundwater, lakes, rivers, streams
Hydrologic cycle: Movement of water in the seas, land, and air. It is driven by solar energy and gravity
Groundwater and Surface Water Critical Resources
Zone of saturation: Spaces in soil are filled with water
Water table: Top of the zone of saturation
Aquifers: Naturally recharge, lateral recharge
Surface Run-off: Precipitation that does not infiltrate the ground or evaporate
Water Shed: The region from which water drains into a body of water
Groundwater: Precipitation that infiltrates the ground and percolates downwards through voids in soil and rocks
Water Footprints
Water footprint: Volume of water we directly and indirectly
The average American uses 260 L per day
Flushing toilets, 27%
Washing clothes, 22%
Taking showers, 17%
Running faucets, 16%
Wasted from leaks, 14%
World’s poorest use 19 liters per day
Causes of Water Shortages
Dry climates
Drought
Too many people using a normal supply of water
Wasteful use of water
30% Earth’s land area experiences severe drought
Will rise to 45% by 2059 from climate change
Potential conflicts/wars over water
Refugees from arid lands
Increased mortality
Is Extracting Groundwater the Answer?
Groundwater Depletion: Worldwide Problem
India, China, and the United States: Three largest grain producers. Overpumping aquifers for the irrigation of crops
India and China
Small farmers drilling tubewells. Effect on the water table
Saudi Arabia
Aquifer depletion and irrigation
Aquifers
Unconfined Aquifer: Aquifer with water table as top
Confined Aquifer: Bounded above and below by semi-permeable beds of rock and clay
Limits future food production
Bigger gap between the rich and the poor
Land subsidence
Mexico City
San Joaquin Valley in California
Groundwater overdrafts near coastal regions
Contamination of groundwater with saltwater
Groundwater Depletion
Prevention
Waste less water
Subsidize water conservation
Limit the number of wells
Do not grow water-intensive crops in dry areas
Control
Raise the price of water to discourage waste
Tax water pumped from wells near surface waters
Set and enforce minimum stream flow levels
Divert surface water in wet years to recharge aquifers
Is Building More Dams the Answer?
Large Dams and Reservoirs
Dams/Reservoirs: They capture and store runoff as well as they release runoff as needed to control:
Floods
Generate electricity
Supply irrigation water
Recreation (reservoirs)
Advantages
Increase the reliable runoff available
Reduce flooding
Grow crops in arid regions
Disadvantages
Displaces people
Flooded regions
Impaired ecological services of rivers
Loss of plant and animal species
Fill up with sediment
This can cause other streams and lakes to dry up
Is Transferring Water from One Place to Another the Answer?
California Transfers Water from Water-Rich Areas to Water-Poor Areas
Water is transferred from north to south by
Tunnels
Aqueducts
Underground pipes
California Water Project: Inefficient water use. Environmental damage to the Sacramento River and San Francisco Bay
Is Converting Salty Seawater to Freshwater the Answer?
Desalination
Desalination: Removing dissolved salts
Distillation: evaporate water, leaving salts behind
Reverse osmosis, microfiltration: use high pressure to remove salts
Removing Salt from Seawater Environmental Costs
Problems
High cost and energy footprint
Keeps down algal growth and kills many marine organisms
Large quantity of brine wastes
How Can We Use Water More Sustainably?
Reducing Water Waste Has Many Benefits
One-half to two-thirds of water is wasted
Subsidies mask the true cost of water
Water conservation
Improves irrigation efficiency
Improves collection efficiency
Uses less in homes and businesses
We Can Cut Water Waste in Irrigation
Flood irrigation
Wasteful
Center pivot, low-pressure sprinkler
Low-energy, precision application sprinklers
Drip or trickle irrigation, micro irrigation
Costly; less water waste
Solutions: Sustainable Water Use
Waste less water and subsidize water conservation
Do not deplete aquifers
Preserve water quality
Protect forests, wetlands, mountain glaciers, watersheds, and other natural systems that store and release water
Raise water prices
Slow population growth
How Can We Reduce the Threat of Flooding?
Flood Plains: Too Much Water
Flood plains: Highly productive wetlands, that provide natural flood and erosion control, maintain high water quality, and recharge groundwater
Benefits of floodplains
Fertile soils
Nearby rivers for use and recreation
Flatlands for urbanization and farming
Human Activities Make Floods Worse
Removal of water-absorbing vegetation
Draining wetlands and building on them
Rising sea levels from global warming mean more coastal flooding
We Can Reduce Flood Risks
Rely more on nature’s systems
Wetlands
Natural vegetation in watersheds
Rely less on engineering devices
Dams
Levees
Channelized streams
Reducing Flood Damage
Prevention
Preserve forests in watersheds
Preserve and restore wetlands in floodplains
Tax development on floodplains
Use floodplains primarily for recharging aquifers, sustainable agriculture, and forestry
Control
Straighten and deepen streams (channelization)
Build levees or floodplains along streams
Build dams