A catchment that is being built to hold treated sewage and flood water at Madiwala lake is the latest addition to the biodiversity park — though it was not a part of the original plan.

In 2015, Karnataka Knowledge Commission had made a recommendation to create a biodiversity park in Bengaluru, and the site near Madiwala lake was chosen for it. The original plan included a terrestrial ecosystem in place of the lake extension. It was only after last year's excessive rainfall, which caused flooding in the nearby low-lying areas, that the government decided to take up the process of extending the lake area.

"After the floods last year, the government said that one of the major aspects in the development of the Madiwala biodiversity park is to enhance the storage capacity of the lake. The rejuvenation and extension of the lake is now a part of the biodiversity park plan," said C R Babu, Emeritus Professor of Delhi University. The construction of the biodiversity park has been undertaken by the Karnataka Lake Conservation and Development Authority (KLCDA) and Prof Babu is helping with the project.

The terrestrial ecosystem, which was supposed to be built in place of the lake enclosure, has been moved to another location near Madiwala lake. The ecosystem will be prohibited to the public and will serve as a conservation zone filled with native plant species.

"Initially the area was supposed to be [an] oxidation pond. We were supposed to develop a terrestrial forest area here. But what happened was that due to the flood last year the present chief executive officer of the Karnataka lakes authority asked us whether we can convert this into a desilt and extend the water body," said Dr. B. S. Padmavati, Project Co-ordinator of the Biodiversity Park.

Lakes get silted over time, which reduces their flood carrying capacity. This causes water to spill onto the low-lying areas when there is heavy rainfall. Around 10 acres of land with a depth of 5 metres are currently being used to desilt the land to increase the lake capacity. The sediment has been used to create an island for grassland birds.

"One of the major functions of the lake ecosystem is to store flood water, to prevent flooding of the low-lying areas. While storing the water, it will also recharge the water. Madiwala lake is critical in the linkage of flood water movement," Prof Babu explained.