First came two years of renovations at a cost of $34 million, then a slow filling, and then the invasion of algae. Now the Reflecting Pool on the National Mall in Washington, D.C., is dry once again while officials ponder how to ensure it does indeed reflect when full.

The problem -- a green growth of algae slowly creeping across the water's surface -- appeared soon after the pool was refilled last month. So, it was drained last week to clean up the scum while water specialists come up with a solution.

The accompanying photos -- the first showing the Reflecting Pool being refilled after two years of renovations, the second of it full and attracting a heron, the third with a layer of algae, and the fourth, it empty once again -- were taken by Washington, D.C., photographer Stephen R. Brown. The last photo was taken this past Friday morning.

Built in the 1920s on marshland without pilings for support, the original pool sank significantly over the years, which caused cracks and leaks. Holding 6.75 million gallons of water, the Reflecting Pool lost an estimated 500,000 gallons a week to leaks and evaporation and required about 30 million gallons of municipal water annually to maintain it. Because it lacked a circulation system, it had to be emptied, cleaned, and refilled twice a year.

The pool was closed in November 2010 for reconstruction, which was made possible with $34 million in funding from the American Recovery and Reinvestment Act.

The new pool is supported underground by more than 2,100 50-foot timbers to prevent it from sinking. It is shallower than the original, holding about 4 million gallons of water. Specially-designed tinted concrete will improve the appearance and reflectivity of the water. The design maintained the footprint of the original structure, and the 580 granite stones that had been placed along the edges of the pool in the 1920s were catalogued and put back into place to maintain the pool’s cultural integrity.

The new pool uses the Tidal Basin as its primary water source, eliminating the reliance on the potable city water supply. However, it did come with that algae problem.