© 2011 pearson education, inc. ap environmental science mr. grant lesson 72 human activities affect...

© 2011 Pearson Education, Inc.

AP Environmental Science

Mr. Grant

Lesson 72

Human Activities Affect Waterways


Mastery Check

Compare and contrast the main types of freshwater ecosystems. Name and describe the major zones of a typical pond or lake.


Objectives:

• Define the term sinkhole.

• Discuss how we use water and alter freshwater systems.

• TED - With wisdom and wit, Anupam Mishra talks about the amazing feats of engineering built centuries ago by the people of India's Golden Desert to harvest water. These structures are still used today -- and are often superior to modern water megaprojects.


Sinkhole:

Define the term sinkhole.


Discuss how we use water and alter freshwater systems.• Water is a renewable but limited resource, so we must manage it

sustainably.

• We use water for agriculture, industry, and residential use. Globally 70% is used for agriculture.

• We pump water from aquifers and surface water bodies, sometimes at unsustainable rates.

• Some of our water extraction now goes to bottled water, which is hugely popular even though it is no healthier than tap water and creates substantial plastic waste.

• We attempt to control floods with dikes and levees.


Discuss how we use water and alter freshwater systems, con’t.

• We divert water with canals and irrigation ditches to bring water to where it is desired.

• We have dammed most of the world’s rivers. Dams bring a diversity of benefits and costs.

• Some dams are now being removed.

• Many wetlands have been lost, and we are now trying to restore some.


Human Activities Affect Waterways

Water is crucial for human health as well as farms and factories

Water is a limited but renewable resource Withdrawal of water in most of the world is

unsustainable We are depleting many sources of surface water and

groundwater

One-third of the world’s people are affected by water shortages


Human Activities Affect Waterways We have achieved impressive engineering

accomplishments to harness fresh water 60% of the world’s largest 227 rivers have been

strongly or moderately affected by dams, dikes, and diversions


Fresh water and human populations are unevenly distributed across Earth Different areas possess different amounts of water

People are not distributed in accordance with water availability

Asia has the most water of any continent but the least water available per person

Densely populated nations like Pakistan, Iran, India, and Egypt face serious water shortages

Fresh water is also unevenly distributed in time Seasonal rains lead to differences in water availability India can receive half of its rain in a single monsoon Dams are used to store water for dry times


Fresh water and human populations are unevenly distributed across Earth

Climate change will worsen conditions in many region Altered precipitation patterns

Melting glaciers causing early season runoff

Intensified droughts and flooding

One-third of the world’s major rivers experienced reduced flow from 1948 to 2004 Attributed largely to climate change


Water supplies households, industry, and especially agriculture Globally, 70% of water is used for agriculture, 20%

for industry, and 10% for residential and municipal use Arid countries use more water for agriculture Developed countries use more water for industry


Water supplies households, industry, and especially agriculture Consumptive use = when water is removed from

an aquifer or surface water body and is not returned Nonconsumptive use = does not remove, or only

temporarily removes, water

Irrigation = is the water applied to crops

Electricity generation at hydroelectric dams


Water supplies households, industry, and especially agriculture Rapid population growth requires more food and clothes

We use 70% more irrigation water than 50 years ago

Irrigation can more than double crop yields 18% of land is irrigated but produces 40% of our crops

Irrigation is highly inefficient Water evaporates in “flood and furrow” irrigation

Overirrigation leads to waterlogging and salinization Reducing world farm income by $11 billion


Governments subsidize irrigation

Farmers in California’s Imperial Valley pay only 1 penny for 220 gallons of water

Water use for agriculture is subsidized by governmentsFarmers have little incentive to conserve


Excessive water withdrawals can drain rivers and lakes

In many places, we are withdrawing water at unsustainable rates

Many of the world’s major rivers regularly run dry before reaching the sea The Colorado River often does not reach the Gulf of

California, threatening the future of cities and farms that rely on its water

Reduced flow drastically changes the river’s ecology and plant community and destroys fish and invertebrates


Excessive water withdrawals can drain rivers and lakes

The Aral Sea in in present day Uzbekistan and Kazakhstan was once the fourth-largest lake on Earth It lost 80% of its volume in 45 years

The two rivers leading into the Aral Sea were diverted to irrigate cotton fields

60,000 fishing jobs are gone

Pesticide-laden dust is blown into the air

Little cotton can grow on the salty soil


The Aral Sea


Excessive water withdrawals can drain rivers and lakes Worldwide, 15%–35% of water withdrawals for agriculture are

unsustainable

Water mining = withdrawing water faster than it is replenished


Groundwater can also be depletedGroundwater is more easily depleted than surface water

Aquifers recharge slowly

Used by one-third of all people

As aquifers are mined, water tables drop

In many areas, water tables are falling 1–3 m/year Salt water

intrudes in coastal areas, making water undrinkable

Land above the aquifers subsides


Groundwater can also be depleted

Sinkholes = areas where ground gives way suddenly Once the soil is compacted, aquifers can’t recharge

Wetlands that get their water from groundwater dry up


Groundwater supplies our bottled water

Groundwater is being withdrawn for use as bottled water An average American drinks 29 gallons/year

Sales topped $15 billion in the United States in 2012

People drink bottled water for portability, convenience They think it tastes better or is healthier

Bottled water is no better than tap water It is heavily packaged and travels long distances using

fossil fuels

Energy costs of bottled water are 1000–2000 times greater than those of tap water

Only 25% of bottles are recycled in the United States


Bottled water is popular but problematic

Energy costs of bottled water are 1,000–2,000 times greater than those of tap water


People build dikes and levees to control floods

Flooding = a normal, natural process where water spills over a river’s banks Spreading nutrient-rich sediments over large areas

In the short term, floods damage property

Levees (or dikes) are the long, raised mounds of earth along the banks of rivers that hold water in channels Stop flooding from most rains

May make floods worse by forcing water to stay in channels, build energy, and then overflow

Dams prevent flooding and change a river’s nature

Releasing water periodically simulates flooding


We build dikes and levees to control floods


Levees increase flooding

A major levee along the Mississippi River failed after Hurricane Katrina, allowing parts of New Orleans to be flooded


We divert surface water to suit our needs

People divert water to farm fields, homes, and cities Water from the Colorado River is diverted to Denver, Las

Vegas, Los Angeles, and elsewhere

In China, $62 billion is being spent to move water from the Yangtze to the Yellow River

Politically strong, water-poor areas forcibly take water from weaker communities

Los Angeles commandeered water from rural areas, turning the environment into desert, creating dustbowls, and destroying the economy In 1941, it diverted streams that fed Mono Lake

Lake levels fell; salt concentrations doubled


Water-poor regions take water from others


We divert surface water for our needs

The once mighty Colorado River has been extensively diverted and used


We have erected thousands of dams

Dam = any obstruction placed in a river or stream to block the flow of water

They create reservoirs = artificial lakes Dams are built to prevent floods, provide drinking

water, allow irrigation, and generate electricity 45,000 large dams have been erected in more than

140 nations

Tens of thousands of smaller dams have been built

Only a few major rivers remain undammed in remote regions of Canada, Alaska, and Russia


We have erected

thousands of dams


A typical dam


We have erected thousands of dams Dams produce a mix of benefits and costs The dam on the Yangtze River is the largest in the

world Its reservoir stretches for 616 km (385 mi)

It provides flood control, passage for boats, and huge amounts of electricity


We have erected thousands of dams

However, it cost $39 billion to build

Flooded 22 cities and the homes of 1.24 million people

Submerged 10,000-year-old archaeological sites

Drowned farmland and wildlife habitat

The tidal marshes at the Yangtze’s mouth are eroding

Pollutants may be trapped, making the water undrinkable


Some dams are being removed Some people feel that the costs of dams outweigh their benefits

and are pushing to dismantle dams

Removing dams will restore riparian ecosystems, reestablish fisheries, and revive river recreation

The Federal Energy Regulatory Commission (FERC) renews licenses for dams

If dam costs exceed benefits, the license may not be renewed

400 dams have been removed in the United States

Some property owners who opposed the removal changed their minds once they saw the healthy river


Wetlands are affected by human manipulations of waterways Wetlands are being lost as we divert and withdraw water,

channelize rivers, build dams, etc.

Wetlands have also been widely drained for agriculture

As wetlands disappear, we lose ecosystem services

Filtering pollutants, wildlife habitat, flood control, etc.

Many are trying to protect and restore them


Wetlands are affected by human manipulations of waterways

The Ramsar Convention on Wetlands of International Importance (1971) seeks the conservation and wise use of wetlands in the context of sustainable development 1900 sites covering 185 million ha are protected


Solutions to Depletion of Fresh Water

Our use of fresh water has doubled over the last 50 years

We can either increase supply or reduce demand Increasing supply through intensive extraction is

only a temporary fix Diversions increase supply in one area but decrease

it elsewhere


TED Video

To promote smart water management, Anupam Mishra works to preserve rural India’s traditional rainwater harvesting techniques.

"In [him] lives a spirit, of quiet service, that once existed freely in our politics and our activism, a spirit that has been completely excised from one sphere and remains gravely threatened in the other."

Ramachandra Guha, in The Hindu

Anupam Mishra: The ancient ingenuity of water harvesting (17:15)

http://www.ted.com/speakers/anupam_mishra.html

© 2011 pearson education, inc. ap environmental science mr. grant lesson 72 human activities affect...

Documents

water solutions

clear water

water extraction

surface water bodies

volume of open water

water temperature decreases

modern water megaprojects

limnetic zone