According to the Longman dictionary (https://www.ldoceonline.com), "rich" is used about people and places, "affluent" is the synonym to "rich", but is more formal and used about societies, groups of people, or areas where people live, where people have nice houses and a lot of expensive possessions ("today’s affluent society"), and with the word "abundant" you'd describe something that exists in large quantities ("an abundant supply of fresh water"). Hope it helped :)

The word "affluent" means "wealth". It is a word used to describe individuals or societies that have money to spend. The word "abundant" means "plenty" and has to do with quantity. For example, a farmer can have an abundant harvest if he has plenty of crops. The word "rich" can be used to describe a person with money, but it is also used frequently to describe the quality of things. For example, the colour of a rug can be a rich if it is a vivid blue. The taste of a cake can be rich if it is made with butter or cream. The sound of a musical recording can be rich if it is full harmony. Hope this helps