Engineers are considering several possible scenarios for Snowy 2.0. One of them would connect the scheme’s largest dam, the Talbingo reservoir, with the Tantangara reservoir to its east with 27 km of new tunnels. The Talbingo reservoir, on the Tumut River, sits 600 metres above sea level and holds 921,400 megalitres. It is the upper reservoir for Snowy’s largest power- plant, Tumut 3, which has been running pumped hydro since 1973. Back then dedicated pumps were needed to drive the water back uphill. Now technology has developed to the point that turbines can do the pumping. All of the Snowy 2.0 turbines will have this ability, a much more cost- effective approach to pumped hydro. The Tantangara reservoir, which dams the Murrumbidgee River, is 1,200 metres above sea level and holds more than 250,000 megalitres. To drill into the already full Tantangara, an inner dam would need to be built to drain around the bore area. The new 2,000 megawatt power station, constructed inside a 200- metre long cavern 800 metres underground, would be the biggest hydro power station in Australia.