The Thalangama tank and its environs were declared as an Environmental Protection Area (EPA) under the National Environmental Act (Gazette Extraordinary No. 1487/10, dated 5th March 2007). The Gazette was amended in 2021 to allow an elevated highway passing the paddy fields and the smaller and more recently constructed Averihena tank.

To improve its water storage capacity, the Thalangama lake underwent the last major dredging and spill-level adjustment around 1989/90 (including the construction of the circular spillway, and drain linking the tank with the Averihena lake and eventually Kelani river), and no longer to the Parliament lake. In 2017-2020 significant areas overgrown by invasive Wel Atha trees were removed and a new [on demand] water outlet under the street near the main bridge and circular spillway constructed.

The word Thalangama is said to derive from the word ‘Thadaka Gama’ or ‘village of ponds or tanks’. But it could also refer to the Thalang or Talan tree (Litsea gardneri).

It is believed that the ancient Thalangama tank was built by King Parakramabahu VI during his reign from ca. 1412 to 1467 AD. It was a bathing place for the elephants of the royal army, and water reservoir for rice cultivation. Still today, it is used to irrigate about 80 ha of paddy, to fish, and wash cows and water buffaloes, while elephants (from nearby temples) bathed in the lake the last time back in the eighties.

It was probably at the same time in 1989/90 when the water in the lake was extremely low to build the circular spillway, that in a ‘night action’ local residents retrieved the last parts (like the engine) of the Japanese aircraft which crashed during the Easter Sunday Raid on Colombo on 5th April 1942 into the overgrown Thalangama lake. In contrast to local expectations, there were no valuables in the wreck, and most metal parts were eventually sold as scrap metal. Eyewitnesses of the plane’s removal confirm that some metal pieces might still be in private hands as souvenirs, and were even exhibited in a local temple.

Among the various historical war records which account for every plane in volved in the raid, only a few mention a Japanese one that came down near Pita Kotte, and only the one by Capt. G A Fernando refers to the Thalangama tank.