1. To prevent drought because South Africa is considered one of the 30 driest countries in the world.
2. To store rainfall (to prevent drought).
3. Dams change daily flows by releasing water as a reaction to demands for irrigation, energy, etc.
If a student fails to recognize how to properly quote the words of an author, that student may be found guilty of plagiarism.
Basic is to luxurious as common is to unique.