Freshwater: Scarcity and Threats

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Questions and Answers

What percentage of the world's freshwater does Canada hold?

10%

20% (correct)

30%

50%

What is the top of the groundwater zone commonly referred to as?

Aquifer

Water table (correct)

Zone of saturation

Surface runoff

Which process replenishes aquifers naturally?

Natural recharge (correct)

Groundwater depletion

Lateral recharge

Surface runoff

What is the process by which water flows across the land surface into bodies of water called?

Surface runoff Signup and view all the answers

What constitutes a watershed or drainage basin?

Land from which surface water drains into a body of water Signup and view all the answers

What percentage of the world's reliable runoff is currently being withdrawn for human use?

34% Signup and view all the answers

Which sector uses the largest portion of the water withdrawn each year?

Irrigation Signup and view all the answers

What phenomenon causes a loss of two-thirds of the annual surface runoff in rivers and streams according to hydrologists?

Seasonal floods Signup and view all the answers

What percentage of the Earth's freshwater is readily available for use?

0.024% Signup and view all the answers

How does excessive withdrawal of water from natural sources affect the environment?

It leads to shrinking lakes. Signup and view all the answers

Why is access to freshwater considered a global health issue?

It affects survival rates due to waterborne diseases. Signup and view all the answers

What is the hydrologic cycle primarily driven by?

Solar energy and gravity. Signup and view all the answers

What major consequence arises from altering precipitation patterns?

Changes in available freshwater resources. Signup and view all the answers

Which groups are typically responsible for water collection in developing countries?

Poor women and girls. Signup and view all the answers

What issue arises due to unequal distribution of freshwater resources?

Divisions between water haves and have-nots. Signup and view all the answers

What critical factor contributes to the threats against the world's freshwater supply?

Withdrawal of water faster than replenishment. Signup and view all the answers

What can result from groundwater overdrafts near coastal areas?

Contaminated groundwater making it undrinkable Signup and view all the answers

Which of the following is a major concern regarding tapping deep aquifers?

Some flow beneath more than one country and lack treaties Signup and view all the answers

What advantage do large dams and reservoirs provide?

They supply water for irrigation and cities Signup and view all the answers

What is one negative effect of building large dams?

Increased displacement of populations Signup and view all the answers

Why might the costs of tapping deep aquifers be concerning?

They could be prohibitively high and remain uncertain Signup and view all the answers

What can happen to reservoirs over time?

They typically fill up with sediment within 50 years Signup and view all the answers

What percentage has the construction of large dams increased annual reliable runoff available for human use?

Nearly 33% Signup and view all the answers

What ecological consequence can arise from the flooding caused by dams?

Destruction of productive land Signup and view all the answers

What is one advantage of large dams and reservoirs?

Provision of drinking water Signup and view all the answers

Which of the following is a disadvantage associated with water transfers?

Ecosystem degradation Signup and view all the answers

What is a significant risk of large dams?

Devastating downstream flooding if the dam fails Signup and view all the answers

Which process uses high pressure to remove salt from water?

Reverse osmosis Signup and view all the answers

What is a major concern regarding the process of desalination?

It kills marine organisms and produces briny wastewater Signup and view all the answers

Why can removing salt from seawater be considered costly?

It involves advanced technology and expensive operations Signup and view all the answers

What is one environmental consequence of large dams?

Loss of nutrient-rich silt for downstream ecosystems Signup and view all the answers

What is a consequence of water transfer for agriculture?

It can lead to water waste Signup and view all the answers

What is a major environmental drawback of desalination?

It creates large quantities of salty wastewater. Signup and view all the answers

What is the most efficient irrigation method mentioned for delivering water to crops?

Drip or trickle irrigation Signup and view all the answers

What contributes significantly to freshwater waste in irrigation?

Loss through evaporation and runoff Signup and view all the answers

Which of the following industries consumes almost 90% of the water used by industry in the United States?

Chemical production Signup and view all the answers

What is a common cause of water loss in major cities of less-developed countries?

Leakage in water mains and pipes Signup and view all the answers

What is the largest use of domestic water in the US?

Flushing toilets Signup and view all the answers

Which factor is a reason for the excessive waste of freshwater?

Low costs of freshwater due to government subsidies Signup and view all the answers

What is suggested as a high government priority to reduce freshwater waste?

Fixing leaks in water systems Signup and view all the answers

Study Notes

Freshwater: A Scarce & Irreplaceable Resource

Freshwater is relatively pure with few dissolved salts.
Although about 71% of the Earth's surface is covered in water, most is saltwater.
Less than 0.024% of Earth's freshwater is readily available for human use.
Most of the world's freshwater is locked in salty oceans, frozen polar ice caps and glaciers, or deep underground in inaccessible locations.
Freshwater is essential for life, with a person able to survive weeks without food but only a few days without water.
The hydrologic cycle, driven by solar energy and gravity, continuously collects, purifies, recycles, and distributes freshwater.

Threats to Freshwater Supply

Water pollution can overload the hydrologic cycle, hindering its natural purification process.
Over-extraction of water from underground and surface sources can deplete supplies faster than they are replenished.
Climate change disrupts long-term precipitation patterns and affects freshwater distribution.

Uneven Distribution of Freshwater

The distribution of freshwater varies considerably across the globe due to rainfall patterns and economic resources.
Some regions are water-rich while others are water-scarce, creating disparities between water "haves" and "have-nots."

Groundwater and Surface Water: Essential Sources

Groundwater originates from precipitation that infiltrates the ground and percolates through soil, gravel, and rock until reaching an impenetrable layer.
The zone of saturation, where spaces are completely filled with water, is located above the water table.
Aquifers are underground layers of sand, gravel, or bedrock where groundwater flows, typically moving very slowly.
Aquifers are replenished through natural recharge from precipitation and lateral recharge from lakes, rivers, and streams.
Surface water refers to freshwater from precipitation and snowmelt that flows across the land surface into various water bodies.
Surface runoff occurs when precipitation does not infiltrate the ground or evaporate.
A watershed, or drainage basin, is the land area from which surface water drains into a specific water body.

Human Consumption of Freshwater

Only one-third of the annual surface runoff in rivers and streams is considered reliable and available for human use.
Human population growth tripled during the 20th century, leading to a sevenfold increase in global water withdrawals and a four-fold increase in per capita withdrawals.
We currently withdraw about 34% of the world's reliable freshwater runoff.

Water Uses and Its Impact

The majority of freshwater withdrawals (70%) are for irrigating crops. Industry accounts for 20% and residences for 10%.
Excessive groundwater withdrawals can lead to:
- Land subsidence, causing damage to infrastructure.
- Saltwater intrusion into freshwater aquifers, rendering water undrinkable.

Deep Aquifers: Opportunities and Concerns

Deep water aquifers hold vast freshwater reserves potentially sufficient for centuries.
However, tapping these ancient deposits presents four major concerns:
- They are nonrenewable and cannot be replenished on a human timescale.
- The ecological and geological impacts of pumping from deep aquifers are largely unknown.
- International treaties governing shared deep aquifers are lacking, potentially leading to conflicts.
- The high cost of tapping deep aquifers remains uncertain.

Managing Water Depletion

Solutions for groundwater depletion include:
- Building more dams to store water and generate hydroelectricity.
- Transferring water between locations, though this can be wasteful and harm ecosystems.
- Desalination, which involves removing salt from seawater but has associated costs, environmental impacts, and produces briny wastewater.

Reducing Freshwater Waste

Various strategies can help reduce freshwater waste:
- Eliminating government subsidies for freshwater, encouraging efficient use.
- Implementing efficient irrigation techniques, including drip irrigation, to minimize water loss.
- Redesigning industrial processes to reduce water consumption.
- Fixing leaks in domestic and industrial water systems to prevent unnecessary water loss.

Key Benefits of Reducing Freshwater Waste

Reduced waste leads to increased water availability, promoting sustainable use and reducing the need for resource-intensive solutions like desalination or water transfers.
Freshwater conservation also plays a crucial role in protecting ecosystems and mitigating the ecological impacts of water scarcity.

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Description

Explore the importance of freshwater as a vital resource and its critical scarcity on Earth. This quiz delves into the hydrologic cycle and the various threats to freshwater supply, including pollution and climate change. Test your knowledge on the impacts of these factors on this irreplaceable resource.