What effect does the water cycle have on third world countries?

First of all, the term 'third world countries' has generally been dropped, and the term 'developing countries' should be used instead. Developing countries typically are less developed than developed countries. This is of relevance to the water cycle, because the water cycle is naturally variable over time and space, and this variability is increasing under climate change. This means that there are often extremes in rainfall, leading to both droughts and floods, particularly in arid regions such as southern Africa. While developed countries have infrastructure and service in place to deal with this variability, such as dams to store water, emergency services to assist during floods and funds to provide disaster relief, developing countries often don't have these resources, and they are therefore often hardest hit.  

The correct answer would be they occur when the sun, moon, and earth are aligned. in spite of their name, these tides occur all year long.