VIJAYAWADA: Nearly 30 years after performing its initial ‘bhoomi puja’ at Gottipadiya, Chief Minister N Chandrababu Naidu will return to the site on August 31 to dedicate Phase-I of the Pula Subbaiah Veligonda Project to the nation. In a rare historical milestone, Naidu, who laid the foundation stone on March 5, 1996, will fulfil a long-standing pledge to the drought-prone populations of the Rayalaseema and coastal hinterlands.
Designed to draw 43.50 TMC of surplus Krishna floodwaters from the foreshore of the Srisailam reservoir at Kollamvagu, the project is unique in its engineering. Unlike other regional floodwater schemes that depend on energy-intensive lift irrigation, Veligonda operates entirely through gravity flow, saving massive power costs over its lifespan.
Water conveyed through twin underground tunnels beneath the Nallamala range will bring permanent relief to chronically arid belts plagued by severe groundwater fluorosis, supplying fluoride-free drinking water to 1,657 habitations across western Prakasam, Nellore, and Kadapa.
Under Phase-I, the state will impound 10.70 TMC of water in the newly formed Nallamala Sagar reservoir. This initial storage will immediately feed 1.19 lakh acres of farmland while supplying safe drinking water to nearly 4 lakh residents en route.
Once Phase-II distribution networks are completed, the ayacut will expand across nine key Assembly constituencies: Yerragondapalem (66,300 acres), Markapur (82,900 acres), Giddalur (59,100 acres), Kanigiri (1,00,400 acres), Darsi (23,000 acres), Kondepi (4,400 acres), Udayagiri (63,000 acres), Atmakur (21,000 acres), and Badvel (27,200 acres).
Speaking to reporters in Markapuram ahead of the launch, Water Resources Minister Nimmala Ramanaidu stated that the government prioritised rehabilitation and resettlement (R&R) alongside civil works.
“Between 2019 and 2024, compensation was released to just 96 project-displaced families. Since taking charge in June 2024, our administration sanctioned over Rs 756 crore to cover 6,110 displaced families, with the remaining 1,115 receiving their settlements this month. We ensured that families relocating from the 11 submerged villages were compensated before filling the reservoir,” Ramanaidu said.
To form the 53.85 TMC Nallamala Sagar reservoir, engineers executed a major design feat by closing just three natural mountain gaps — Sunkesula, Gottipadiya and Kakarla — spanning a combined 1.46 km with 14.77 lakh cubic metres of concrete.
Executing civil works at the Kollamvagu inlet site involved severe operational constraints. Located deep inside the Nagarjunasagar-Srisailam Tiger Reserve, all heavy machinery, concrete batching materials, and personnel had to be transported across Srisailam backwaters using water barges (punts).
To keep excavation uninterrupted during high reservoir water levels, engineers sank a 25-metre vertical shaft between the head regulators.
The twin intake tunnels rank among the longest underground conduits in Asia, designed to carry floodwaters through complex geological strata. Tunnel-1 measures 18.82 km in length with a 7-metre finished diameter, engineered for a discharge capacity of 3,001 cusecs.
During its excavation, workers encountered a soft fault zone at Km 3.389 that jammed the Tunnel Boring Machine’s cutter head, completely halting progress for 16 months.
The crisis was eventually resolved when Swiss and Italian tunnelling experts bored an overhead bypass tunnel to inject resin and foam grout, successfully consolidating the loose rock.
Running parallel to it, Tunnel-2 spans 18.787 km with a wider 9.2-metre finished diameter, built to handle a heavy discharge of 8,580 cusecs of water.
Upon exiting these tunnels, the water flows into a 21.8-km feeder canal, where crews constructed a 15-metre-high, 5.3-km concrete retaining wall along the hill toe to protect the canal banks against potential landslips.
First conceived in 1989 following reports by eminent engineer Dr Kuditapudi Srirama Krishnaiah, the project traces its political roots to 1978, when former Markapuram MLA Poola Subbaiah launched public agitations demanding Krishna river diversion.
Between June 2024 and August 2026, the state government infused Rs 2,402 crore to clear pending R&R dues, complete TBM dismantling, and finish feeder canal lining.