Section 39. The water resources commission may, from the proceeds of bond issues authorized for water pollution control, construct or expand reservoirs at locations throughout the commonwealth for the purpose of providing low flow augmentations in time of drought and in such other times as rivers and streams may require additional water flow to carry off treated effluents discharged into said rivers and streams. The commission, in behalf of the commonwealth, may take by eminent domain under chapter seventy-nine or acquire by purchase, gift, or otherwise any land, water rights, or other easements, public or private, necessary for accomplishing the purpose of this section; provided that no taking may be made of water which is used for municipal, agriculture or industrial water supply purposes. The commission may enter into agreements with any federal agency to accept any federal grants that may be available for the aforesaid purpose. Such a reservoir shall not be used for public water supply purposes unless its location, design, and operation, and any subsequent treatment or purification shall be approved by the department of public health.