Do Now:

• 30 Million people in 7 states depend on water from the Colorado River basin. We know that during drought years this severely affects the way of life for millions. Is there a solution/alternative for water in this these states? Explain your answer in complete sentences.

Aim: Is extracting groundwater the answer?

Concept 13-2 Groundwater used to supply cities and grow food is being pumped from

aquifers in some areas faster than it is renewed by precipitation.

Memory Check

• What is groundwater and where is it stored?

Groundwater is Being Withdrawn Faster Than It Is Replenished

• Most aquifers are renewable

• Aquifers provide drinking water for half the world

• Water tables are falling in many parts of the world, primarily from crop irrigation

Groundwater is Being Withdrawn Faster Than It Is Replenished

• India, China, and the United States– Three largest grain producers– Overpumping aquifers for irrigation of crops

• India and China– Small farmers drilling tubewells – Effect on water table

• Saudi Arabia– Aquifer depletion and irrigation

• Do you understand how groundwater is being withdrawn faster then it can be replenished?

Trade-Offs: Withdrawing Groundwater, Advantages and Disadvantages

Natural Capital Degradation: Irrigation in Saudi Arabia Using an Aquifer

Read A Loud: Ogallala Aquifer

Case Study: Aquifer Depletion in the United States

• Ogallala aquifer: largest known aquifer– Irrigates the Great Plains– Very slow recharge– Water table dropping– Government subsidies to continue farming

deplete the aquifer further– Biodiversity threatened in some areas

• California Central Valley: serious water depletion

Natural Capital Degradation: Areas of Greatest Aquifer Depletion in the U.S.

Kansas Crops Irrigated by the Ogallala Aquifer

Overpumping Aquifers Has Several Harmful Effects

• 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

Subsidence in the San Joaquin Valley

Solutions: Groundwater Depletion, Prevention and Control

Deep Aquifers Might Be Tapped

• May contain enough water to provide for billions of people for centuries

• Major concerns1. Nonrenewable2. Little is known about the geological and

ecological impacts of pumping deep aquifers3. Some flow beneath more than one country4. Costs of tapping are unknown and could be high

Summary

• What are three things you can do to promote more sustainable use of the Ogallala Aquifer and groundwater in general?

Homework

• Read pages 328-343• Answer the questions on the worksheet • Answer critical thinking questions 4 and 9.