Markonahalli Dam is built across the river Shimsha in the Kunigal Taluk of Tumkur district. It was built by Krishnaraja Wodeyar IV, the king of Mysore under the guidance of his Diwan, Sir M Visweswaraiah. It was built to irrigate 6,070 hectares of land and has a masonry structure of 139 m and a pair of earth dams extending to 1,470 metres on either side.
What makes this place interesting is the water siphoning system which Sir M.Visweswaraiah designed in the early 1900’s. This system does not use any electricity or man power to control the outlet of water from the dam into the canals. Designed more than a century back, this system still works without a hitch and makes one realize what being an actual engineer means. What nation building means and what genius means. This is a nice place to get out of the city, have lunch under the tamrind trees and relax for a few hours with family or friends.
The reservoir has a catchment area of 4,103 km2 (1,584 sq mi) and can hold a volume of 68 million m³ of water at a full reservoir level of 731.57 m above the mean sea level.
As much as 27 species of fish, including 13 species of commercial fishes have been recorded in the reservoir with Puntius being the dominant species. Labeo calbasu and Cirrhinus Reba and other transplanted carps are also found here. However, the dam is maintained poorly. In 2000, a part of the dam had to be demolished to prevent floods and save 25 villages.
Water started overflowing the dam and only 1 crest gate could be opened. Nearly 150 feet of the dam was demolished to allow excess water to flow out.
Markonahalli Dam – A Popular Fishery
Twenty-seven species of fishes have been recorded from the reservoir, among which 13 contribute to the commercial catch. Puntius has the maximum species diversity with five species.
Even after 55 years of its existence, the reservoir sustains populations of indigenous fish species such as P. Dorsalis, Puntius sarana, and Labeo calbasu and Cirrhinus reba along with the transplanted carps. The fishery management should address the problems in enhancing the productivity of endemic fishes and the stocking should be limited to the extent of filling the vacant niches.