one example:

appreciable increasing of the present withdrawals is possible, however, it is at the cost of dispersing additional ***pumping fields*** to distant areas: the Western Great Erg and the confines of the Eastern Erg...
http://unesdoc.unesco.org/images/0014/001469/146997e.pdf

which comes from these search results:
http://www.google.es/search?hl=es&rlz=1W1ACPW_es&q=hydrogeol...

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Note added at 1 hr (2009-08-29 16:45:39 GMT)
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"calculation of pumping fields and interferences"

Just a thought - "Cálculo de campo" singular (or both plural) would be interpreted as field calculation (s) i.e. in the field, during fieldwork.

This would fit for geolo/hydro if that's a typo ;)

Otherwise, wouldn't it be "Pumping and interference calculation"?

Interference Due to Neighboring Wells During Pumping Tests - [ Traducir esta página ]wells that are likely to cause interference, pumping should be maintained at a steady rate both for a ... calculate the errors from equation (8). For ...
doi.wiley.com/10.1111/j.1745-6584.1985.tb00781.x - Similares

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Note added at 18 hrs (2009-08-30 09:50:18 GMT)
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Sorry - should be "Cálculos de campo not Cálculos de campos - too mant S's ;)