Droughts and floods: too little, too much
Rain is useful, but too much or too little of it causes trouble. When a river receives much more water than its banks can hold, the water spills over onto the land around it. This is a flood. Floods can damage houses and roads, wash away crops and make life hard for many families. The opposite problem is a drought: a long period with so little rain that there is not enough water for people, plants, animals, farms and cities. In a drought crops dry out and farmers may have less to harvest. Long ago the Nile rose every year and left dark, rich silt on the fields, so some places even depend on regular floods. But a sudden, very big flood that nobody expects does the most harm. Remember that one dry week is not a drought, and one hot day does not prove that the climate has changed: scientists look at many years.
| Problem | Too little rain | Too much rain |
|---|---|---|
| Name | drought | flood |
| Crops | dry out | washed away |
| Rivers | low | overflow |
Two trays. With a grown-up, put the same amount of soil in two trays. Pour a little water on one tray and a very large amount on the other tray (outdoors or in a sink). Describe what happens to the soil and to a few seeds you placed on top. Which tray models a flood and which models a dry spell?