freshwater
water that contains very low levels of dissolved salts
access to freshwater is a
global health issue, economic issue, national and global security issue, environmental issue
how much of earths water supply is readily available
.024%
groundwater
freshwater found in underground spaces
zone of saturation
zone where all open spaces in sediment and rock are completely filled with water
water table
the top layer of the zone of saturation
-falls in dry weather, when we remove groundwater faster than nature can replenish it
-rises in wet weather
aquifers
caverns and porous layers of sand, gravel, or rock through which groundwater flows
-most are replenished naturally by precipitation
deep aquifers
were filled with water by glaciers that melted thousands of years ago
-cannot be recharged
surface water
the freshwater from rain and melted snow that flows or is stored in lakes, reservoirs, wetlands, streams, and rivers
surface runoff
precipitation that does not return to the atmosphere by evaporation
watershed
The land from which surface water drains into a particular river, lake, wetland, or other body of water.
hydrologists
study water and its properties and movement
reliable surface runoff
water we can count on as a source of freshwater from year to year.
water footprint
rough measure of the volume of freshwater that we use or pollute, directly or indirectly, to stay alive and to support our lifestyles
virtual water
the freshwater that is not directly consumed but is used to produce food and other products
largest water footprints
india, us, china
freshwater scarcity stress
measure based on the amount of freshwater available compared to the amount used for human purposes
Aquifers provide drinking water for how much of the world's population?
1/2
overpumping of aquifers
contributes to limits on food production, rising food prices, and widening gaps between the rich and poor in some areas
land subsidence
the sinking or settling of land to a lower level in response to withdrawing large amounts of groundwater
5 problems with tapping deep aquifers
1. nonrenewable
2. little is known about geological and ecological impacts of pumping large amounts of freshwater
3. no international treaties govern access to these aquifers that flow beneath 1 or more countries
4. costs could be high
5. much of the wate
dam
a structure built across a river to control the river's flow
reservoir
Artificial lake created when a stream is dammed.
-purpose is to store surface runoff and release it to control floods, generate electricity, and to supply freshwater for irrigation
Desalination
the process of removing dissolved salts from sea water in aquifers or lankes
Distillation
involves heating saltwater until it evaporates and condenses as freshwater
reverse osmosis
uses high pressure to force saltwater through a membrane filter with pores small enough to remove the salt
3major problems with desalination
1. high cost
2. requires use of chemicals
3. produces huge quantities of wastewater
snowpacks
bodies of densely packed, slowly melting snow
y we have major losses of freshwater
1. freshwater to most uses is low due to gov subsidies
2. lack of gov subsidies for improving the efficiency of water use
flood irrigation
water is pumped from a groundwater or surface water source through unlined ditches where it flows by gravity to the crops being watered
-most used and inefficient
spray irrigation
sprays huge volumes of water onto large fields and as much as 40% is lost
center pivot irrigation
-Uses pumps to spray water on a crop
-Allows 80% of water to reach crops
drip irrigation
the practice of using small pipes that slowly drip water just above ground to conserve water to use for crops
-90-95% reaches crops
flushing toilets with freshwater
largest use of domestic freshwater in us
gray water
wastewater from baths, showers, bathrooms, and washing machines
floodplain
The land adjacent to a river flood
flood benefits
created some of the worlds most productive farmland by depositing nutrient rich silt on floodplains, help recharge groundwater and refill wetlands that are commonly found on floodplains
Human Activities that increase flooding
1. removal of water absorbing vegetation
2. draining of wetlands
we can reduce floods
-channelization
-levees
-damming
- preserve existing wetlands and restore degraded ones
water pollution
any change in water quality that can harm living organisms or make the water unfit for human uses such as drinking, irrigation, and recreation
point source
discharge pollutants at specific locations through drain pipes, ditches, or sewer lines that are easy to identify monitor, and regulate
-factories
nonpoint sources
are broad and diffuse areas where rainfall or snowmelt washes pollutants off the land into bodies of surface water. Difficult to control
-runoff of eroded soil
-chemicals from cropland, etc
leading cause of water pollution
agricultural activities
most common pollutant
sediment eroded from ag land
wastewater
water that contains waste from homes or industry
most serious threats to us stream and lake water quality
mercury, pathogens from leaking and broken sewage pipes, sediment from land disturbance and stream erosion, metals, nutrients that cause oxygen depletion
oxygen sag curve
breakdown of biodegradable wastes by bacteria depletes dissolved oxygen
Lakes and reservoirs are less effective at diliuting pollutants than streams b/c
1. often contain stratified layers that undergo little vertical mixing
2.they have low flow rates or no flow at all
Eutrophication
is the natural nutrient enrichment of a shallow lake, a coastal area at the mouth of a river or a slow-moving stream
Olgiotrophic Lake
low in nutrients and clear water
cultural eutrophication
human activities can greatly accelerate the input of plant nutrients to a lake
How to prevent cultural eutrophication
1. advanced waste treatment processes
2. mimic earths natural cycling of nutrients by recycling the removed nutrients to the soil instead of dumping them into waterways
Maximum contaminant level (MCL)
The standard for safe drinking water established by the EPA under the Safe Drinking Water Act
3 recommendations for us safe drinking water act
1. combine many of the drinking water treatment systems that serve fewer than 3,300 people with nearby larger systems to make it easier for these smaller systems to mee fed standards
2. strengthen and enforce requirements concerning public notification of
harmful algal blooms
release waterborne and airborne toxins that poison seafood, damage fisheries, kill fish eating birds, reduce tourism
crude petroleum
oil as it comes out of the ground
refined petroleum
fuel oil, gasoline, and other processed petroleum products
largest source of oil pollution from human activities
urban and industrial runoff
ways to reduce nonpoint
-Reducing soil erosion and fertilizer runoff by keeping cropland covered with vegetation and using conservation tillage and other soil conservation methods
-Using fertilizers that release plant nutrients slowly.
-Using no fertilizers on steeply sloped lan
septic tank
A large container that receives wastewater from a house as part of a septic system
primary sewage treatment
a physical process that uses screens and a grit tank to remove large floating objects and to allow solids such as sand and rock to settle out
secondary sewage treatment
a biological process in which oxygen is added to the sewage in an aeration tank to encourage aerobic bacteria to decompose as much as 90% of dissolved and biodegradable, oxygen-demanding organic wastes
advanced sewage treatment
uses a series of specialized chemical and physical processes to remove specific pollutants left in the water after primary and secondary treatment.