Intensive use of groundwater in North America

From the permafrost of Canada’s High Arctic to the tropical humid forests of Mexico’s Yucatán Peninsula, the North American continent contains a remarkable diversity of climatic regimes, landscapes, and ecosystems. The abundant precipitation characterizing Southern Mexico and coastal areas of the USA and Canada contrasts with the arid climates of the Southwestern USA and Northern Mexico. The availability of groundwater and surface water also varies considerably. In Canada, 30% of the population relies on groundwater for all uses combined. The USA used about 471,000 Mm 3 of freshwater in 1995 to meet the needs of its 300 million inhabitants. About 105,000 Mm 3 was obtained from groundwater. In Mexico, groundwater provides 39% of the water supply. Both Mexico and the USA are experiencing problems associated with groundwater pumpage –especially in the large population centers and agricultural regions that are located in arid climates. Three selected groundwater examples are described in this chapter, one for each country, to show the importance of groundwater in North America: land subsidence in Mexico City; the overexploitation of the Floridan aquifer in the USA; and the issue of transboundary water and water exports in Canada.