Section 2. As used in this chapter, the following words shall, unless the context clearly indicates otherwise, have the following meanings:—

''Annual statement of withdrawal'', an annual statement of the volume of water a person is withdrawing pursuant to a registration statement or permit, filed with the department in accordance with section five or eleven and the regulations adopted thereunder.

''Commission'', the water resources commission of the executive office of environmental affairs.

''Department'', the department of environmental protection.

''Existing withdrawal'', except as provided in section five, the average volume of water withdrawn from a particular water source during the five years prior to January, nineteen hundred and eighty-six; provided, however, that if, during such period of five years, withdrawals from the water source have been interrupted due to contamination of the water source, the periods of such interruptions shall be excluded pro rata from the computation of existing withdrawal; and, provided further, that no person shall be deemed to have an existing withdrawal unless such person files a registration statement and an annual statement of withdrawal with the department, in accordance with the provisions of section five and section six and the regulations adopted thereunder.

''New withdrawal'', any withdrawal of water which is not an existing withdrawal.

''Nonconsumptive use'', any use of water which results in its being discharged back into the same river basin, as defined by the water resources commission, in substantially unimpaired quality and which conforms to the definition adopted by regulation pursuant to section four.

''Permit'', a permit issued by the department under section seven and authorizing the withdrawal of water in excess of the threshold volume.

''Person'', any agency or political subdivision of the federal government or the commonwealth, any state, public or private corporation or authority, individual, trust, firm, joint stock company, partnership, association, or other entity, and any officer, employee or agent of said person, and any group of said persons.

''Public water system'', a system for the provision to the public of piped water for human consumption, if such system has at least fifteen service connections or regularly serves an average of at least twenty-five individuals daily at least sixty days of the year. Such term shall include any collection, treatment, storage, and distribution facilities under control of the operator of such a system and used primarily in connection with such system, and any collection or pretreatment storage facilities not under such control which are used primarily in connection with such system.

''Registration statement'', a statement of an existing withdrawal, filed with the department in accordance with section five and the regulations adopted thereunder.

''Safe yield'', the maximum dependable withdrawals that can be made continuously from a water source including ground or surface water during a period of years in which the probable driest period or period of greatest water deficiency is likely to occur; provided, however, that such dependability is relative and is a function of storage and drought probability.

''Threshold volume'', the volume of water specified in section four or the regulations adopted thereunder.

''Water'', all water beneath or on the surface of the ground whether wholly or partly within the commonwealth.

''Water resources management plan'', a local plan to meet water needs within a city or town, submitted by the chief elected official or designee to the commission pursuant to the regulations of the commission.

''Water resources management official'', the local official, designated by the chief elected official within a city or town, responsible for submitting and administering the water resources management plan in that city or town.

''Water source'', any natural or artificial aquifer or body of surface water, including its watershed where ground and surface water sources are interconnected in a single hydrological system.

''Withdrawal'' or ''withdrawal of water'', the removal or taking of water from a water source; provided, however, that all removals or takings of water from a particular water source which are made or controlled by a single person shall be deemed to be a single withdrawal of water.