THE PROBLEM
- Irrigation by pumping groundwater is producing a gradual depletion of the water table.
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In 1997, Mexico's Comision Nacional del Agua (National Water Commission) estimated the mean annual water table decrease at 0.3 m.
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Currently, the water table lies at a depth of more than 30 m in some places.
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By contrast, in the 1960's, the water table was very close to the surface in some places, feeding wetlands and riparian vegetation.
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Now, these wetlands have all but disappeared, and the valley's landscape has changed from isolated trees and chaparral shrubs to intensively irrigated fields.
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As the water table descends, the costs associated with pumping increase in proportion to the depth.
Eventually, the pumping costs become prohibitive for the local actors, i.e., the ejido proprietors.
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The ejido proprietors are being forced to rent their lands to large packing companies which operate with more capital, or to sell their land,
changing the structure of land ownership.
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