(Reuters) – Russia and Ukraine have accused each other of planning to blow up the Kakhovka hydro-electric dam on the Dnipro River, a step that would unleash a devastating flood across a large area of southern Ukraine. What is the Kakhovka dam, is it about to be blown and what impact would that have? SIGNIFICANCE OF THE DAM * The dam, 30 metres (yards) tall and 3.2 km (2 miles) long, was built in 1956 on the Dnipro river as part of the Kakhovka hydroelectric power plant. * It holds an 18 km3 reservoir which also supplies water to the Crimean peninsula, annexed by Russia in 2014, and to the Zapo…