The actress conceived daughter Sunday Rose, 11 months, after swimming in the Kununurra pools while filming Australia in 2007.
At least six other women fell pregnant on set, leading Nicole, 42, to state: 'There is something in the Kununurra water.'
Her comments have sparked a surge in pleas to the tourist board.
'We try to dissuade these women from being sent the water because of the difficulties of collecting and transporting it,' says a spokeswoman.
'We encourage them to come here for a swim if that's what they want.'
Meanwhile, Nicole's husband Keith Urban, 41, has dismissed reports they're expecting another child.
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