according to conagua almost twothirds of the annual mms rainfall occurs between july and september but leaves chihuahua as the fifth driest state in mexico by almost billion people almost half of the world s population are projected to live in areas with severe levels of water scarcity oecd b although oecd countries are for the most part not as severely affected as the rest of the world mexico is among the oecd countries that will be the most affected mexico is already one of the oecd countries with the largest per capita water consumption