Limón Dam, Embankment dam in Pomahuaca District, Peru

Limón Dam is a 43-metre-high, 320-metre-long concrete-face rock-fill embankment dam on the Huancabamba River, south of Guabal. Its reservoir impounds 44 million cubic metres of water, which is diverted through the 20-kilometre Olmos Transandino tunnel to the Olmos River valley for irrigation and hydropower.

Planning for water diversion in this region began during the 1920s as a response to chronic water shortages. Construction of the dam itself took place in the early 2000s to finally address agricultural water needs in the area.

The dam forms part of the Olmos Transandino Project, transforming agricultural practices for communities across 43,500 hectares of previously arid farmland.

The dam sits on the Huancabamba River south of the small town of Guabal, reached from the Olmos side via the road toward Pomahuaca. The 20 km Olmos Transandino tunnel outlet and the Olmos River channel lie downstream to the west, where diverted water first irrigates 5,500 hectares. The reservoir began impounding in 2009, so water levels vary with the transfer regime.

The Olmos Transandino tunnel was finished on 20 December 2011 at a ceremony attended by President Ollanta Humala. Of its 20 km length, 12.5 km were bored by a tunnel boring machine, while the rest was excavated by other methods. The project was profiled on the TV series Build it Bigger in 2009 and Strip the City in 2014.