Board of Water Supply. Mount Prospect Water Tower. Grand Army Plaza at entrance to Prospect Park. Before Catskill water reached Brooklyn in 1916, the borough received its water from areas of Long Island. The Mount Prospect Reservoir was completed in 1858 to serve the highest parts of Brooklyn, and a tower designed by Thayer and Wallace was built in 1893 to improve water pressure. Once the Catskill system was in place, the reservoir and water tower were still used but gradually phased out. The tower was demolished in 1930 and the reservoir was dismantled ten years later. April 21, 1912.