Which aquifer is the largest in the southwestern United States and is depleting due to irrigation?

• A. A pristine aquifer located in the Northeast
• B. The largest aquifer located in the southwest that is depleting due to agricultural irrigation
• C. An underground reservoir in the Midwest with stable levels
• D. A shallow aquifer in the Southeast with minimal extraction

Answer: (B)

Groundwater depletion happens when water is pumped out for irrigation faster than it can be naturally recharged. The largest aquifer in the southwestern United States, the High Plains or Ogallala Aquifer, underlies parts of eight states and has been heavily used for irrigation to support farming. Because withdrawals have exceeded recharge for many decades, water levels have dropped significantly in many areas, making wells deeper and pumping more expensive, and affecting surface water flows and land stability in some places. That description fits the choice that identifies this as the largest southwestern aquifer and notes its depletion due to agricultural irrigation. The other options describe regions or conditions that don’t match this well-documented situation.