Though parts of northern Mexico are arid, the country as a whole receives an average of 760 mm of precipitation a year (slightly over 30 in). This is a considerable amount, more than that received by either Canada or the USA. However, 73% of Mexico’s rainfall either evaporates directly or or is lost from plants via evapotranspiration. About 25% runs off into rivers and lakes. Only roughly 2% seeps down to recharge subterranean aquifers.
Availability of water per person is a function of population size and the total amount of water available. Though Mexico gets more rain than the USA or Canada, the availability of water per person in Mexico is only one-twelfth that of Canada and about half that of the USA because Mexico’s population density is far higher. In other words, though each square kilometer in Mexico receives more rain on average, that rain must be divided among more people. Of 177 countries analyzed by the FAO, Mexico ranked 90th in terms of water availability per person. However, if Mexico is divided into two zones, the south would rank 51st and the north would rank 131st.
Within Mexico, the Lerma Basin (between Mexico City and Guadalajara) has only about 1/3rd the national average for water availability, while the very heavily populated Valley of Mexico (containing the Mexico City Metropolitan Area) has only 1/30th the national average.
Mexico’s per person consumption of water is about half that of Canada but with proportionately more allocated to agriculture. Nationally, about 75% of water consumption is used in agriculture, while settlements and industry use about 17% and 8% respectively.
Mexico’s water resources and water-related issues are the subject of chapters 6 and 7 of Geo-Mexico: the geography and dynamics of modern Mexico. Ask your library to buy a copy of this handy reference guide to all aspects of Mexico’s geography today! Better yet, order your own copy…