Agriculture contributes to two kinds of degradation of ground water – pollution with
agricultural chemicals and depletion. For example, tests of well water in the Yaqui valley of
Sonora showed the presence of certain pesticides at 5 to 10 times the rates regarded as safe by
the U.S. Environmental Protection Agency (Bray). Overpumping of aquafers in some regions
has drawn down aquifers, especially in the arid north