No person shall have the power to take or withdraw water without first obtaining a permit from the Commissioner conferring an appropriation right; provided, that this section shall not apply to any person taking or withdrawing less than 500 gallons per day for beneficial use; and provided, further, that existing users of water may continue to take or withdraw water to the extent of their vested right without a permit until 90 days after the promulgation of regulations by the Commissioner governing the issuance of permits, as provided in section 154 of this title, and thereafter so long as an application for a permit embodying these rights has been filed.