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violate water quality drinking standards, including arsenic and nitrate levels
In
particular, nitrate contamination in the Tulare Lake Basin and the Salinas Valley
are well documented. Decades of discharge containing fertilizers, pesticides as
well as municipal sewerage with selenium and fluoride, have contributed to
contaminate the San Joaquin River. Salinity problems derived from irrigation
practices have also contributed to its intrusion in this river delta and the Suisun Bay
(Sereno
et al.
, undated; CCWD, 2010).
Regarding Mexico, two agricultural districts, i.e. Hermosillo,
along with Caborca
concentrate most of table grape production in Sonora. In both cases, production
takes place under irrigation. The Hermosillo district, named after the city, which is
also the capital state city, is located in the central part of Sonora, over the Costa de
Hermosillo aquifer. Its rainfall ranges between 75 to 200 mm on average per year
(Vega-Granillo
et al.
2011). This region faces severe problems of aquifer
overexploitation. In 2009, withdrawals were calculated at 431 million of cubic
6
EPA (2013).
7
Comprises the municipality of Hermosillo itself, as well as San Miguel de
Horcasitas and Carbó.
8
Encompassing the municipalities of Caborca itself, Altar as well as Pitiquito.