When does a drought occur?

Explanation

**Step-by-Step Solution:**

1. **Definition of Drought**: A drought is a prolonged period of abnormally low rainfall, leading to a shortage of water.

2. **Lack of Rainfall**: Drought occurs when there is little to no rainfall over an extended period. This can last for months or even years.

3. **Impact on Soil and Groundwater**: When there is insufficient rainfall, the moisture in the soil diminishes. This means that plants cannot get the water they need to grow, leading to dry and barren land.

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