Mexico’s climate varies, from arid regions in the northeast to tropical zones in the southeast. The annual distribution of rainfall is irregular, with almost 80% occurring between July and September and the country’s water resources are unevenly distributed, with 67% of surface water located in the southeastern part of the country with 24% of the population and little industry.
Mexico is a water rich country, receiving around 30 inches of rainwater annually and this rainwater provides more than 4,800 m3 per capita. There is a regional disparity between water recepts and population, with only 4% of the annual rainfall reaching the northern 30% of the country. The central region, where 60% of the population lives, receives only 25% of the total annual rainfall. The southeast and the coastal regions receive more than half of the total annual rainfall.
About 65% of the mean annual runoff (annual surface runoff is estimated at 410 billion cubic metres) is allocated to hydropower generation, 29% to agriculture and 6% to industry and urban areas. A total of 28 billion cubic metres of groundwater is extracted annually, of which 68% is used for irrigation, 20% for urban domestic use, 7% for industry and 5% for rural domestic and livestock demands.
Major water problems are excessive withdrawals from aquifers, water contamination and conflicts among users. In the overpopulated central highlands, both surface and groundwater are becoming increasingly scarce due to economic development and the rapidly growing population, and water pollution and ecological damage are a result. Financial constraints have also been another major concern with the existing government policy to subsidise the water sector.
Given the mounting problems faced by the water sector, the federal government began a restructuring of both its water entities and strategies at the end of the 1980s. Government policy had focused on building large public works, but it could no longer finance such large projects alone.