The Lee scheme was the last of the large-scale hydroelectric projects to be built, following the Shannon, Erne and Liffey schemes. For the politicians and policy makers, those projects were visionary. The generators that were built in the 1950s are still working today. They receive regular overhauls every year. Their basic structure is exactly the same. At Inniscarra, there is generator no 1, a 15 mW unit manufactured by Brown Bovari. Inniscarra generator no 2 is a 4 mW unit also manufactured by Brown Bovari. Carrigadrohid generator no 3 is an 8 mW unit manufactured by Siemens. The manufacturer of all three turbines was J.M. Voith, Germany.

Technology has improved through the years and has been incorporated into the Lee stations. In the 1970s, auto rain recorders were installed at Inniscarra and Carrigadrohid. In the early 1980s improved catchment radio rain recorders were put in – these give advanced warning to predict changes in the flow of water. The 1990s coincided with the refurbishment of switchgear, the replacement of instrumentation, the PLC control of Carrigadrohid, and the refurbishment of spillway gates and sluice gates.

In 1998, the PLC automation of Inniscarra plant and automation of both Inniscarra units were set up to allow one-man operation of the Lee dams. During 2004, further automation and remote control systems were installed to enable the Lee stations to be remotely operated from a central hydro centre at Turlough Hill in the Wicklow Mountains. The introduction of the OTT system means that staff can now pick up hydrometric information from their mobile phones.

The 1990s coincided with the refurbishment of switchgear, the replacement of instrumentation, the PLC control of Carrigadrohid, and the refurbishment of spillway gates and sluice gates. In 1998, the PLC automation of Inniscarra plant was set up. The introduction of the OTT system means that staff can now monitor changes from their mobile phones.

Safety is paramount at the Lee stations, and the care of the dam structure, people, environment, property and plant is essential. There are three operating modes. Firstly, there is the normal operation mode, which is the week-to-week routine work. Operational targets are passed to the national grid and used when needed at peak daily consumption times. Secondly, there is the operating mode for low flow conditions. We use storage of water during the start of the year to accommodate electricity supply to the city during the summer period when the water levels and inflows are low.

The third operation mode is put into place in the event of flooding. The Lee scheme does not eliminate flooding but does have a major effect on reducing floods. When inflows in the catchment exceed the capacity of the turbines to discharge water, lake levels will rise. If inflows and levels continue to rise, a decision may be made to spill the excess water through the sluice gates at Carrigadrohid or the spillways at Inniscarra. Both dams have spillways to spill extra waters. A new bypass spillway was built in the early 1990s at Carrigadrohid to accommodate a one-in-ten-thousand-year flood. The river Lee has a quite short and a flashy catchment of 306 square miles. Floods can be very quick and violent. There is a six- to eight-hour response time. Inniscarra Lake has a maximum storage of twenty million cubic metres whilst Carrigadrohid Lake has a maximum storage of twenty-five million cubic metres. The average rainfall per annum is sixty inches.

When the reservoir lakes are full, there is no option but to spill water downriver. The stations are manned up for twenty-four hours if a flood is imminent, until the flood has receded. It may become necessary to spill floodwater through the spillway gates at Inniscarra or through the sluice gates at Carrigadrohid, although there is enough storage in the lake to take small flash floods. A flood can be halved passing through Inniscarra dam. However, the Lee in areas downstream such as Carrigrohane is a natural floodwater basin. The dams reduce flooding but cannot eliminate the risk. There is tremendous expertise in the dam to cope with these scenarios, and a long list of people to inform downstream in the event of flooding.