The board of supervisors of a county of over 4,000,000 population, without complying with any other provision of law, may transfer with or without consideration and upon such terms and conditions as it determines, any easement, license or other interest in real property belonging to the county and not needed for county purposes to any water agency for such purposes as are consistent with the powers and duties of such districts or agencies.

Any such donation or transfer may be by way of grant, quitclaim, dedication, lease or license.

Any such donation or transfer for less than the full market value of the interest conveyed is hereby declared to be for a public purpose.