Avalanche Lake Ooty:
Avalanche Lake (Avalanchi lake) is located 28 kilometers from Ooty in the Nilgiris district in Tamil Nadu. The lake derived the name avalanche because of a huge land slide (avalanche) that occurred in the region in the early 1800.
Avalanche Lake is an important tourism destination in the Nilgiris district. The lake is surrounded by a rolling landscape with blooming flowers like magnolias, orchids and rhododendrons. Tourists can traverse beside the lake through winding paths around the lake. Tourists visiting the lake can also engage themselves in Trout fishing. A trout hatchery is established near the lake, from where visitors can get fishing rods and other fishing accessories required for trout fishing. The lake is also used by tourists as a camp site wherein they pitch tents near the lake. Other tourist activities in the area include rafting across the lake and trekking the nearby hilly regions like Upper Bhavani where there are thick forests and untouched wild habitats.
Emerald Lake, Ooty:
Emerald Lake is adjacent to Avalanche Lake, in fact they are connected.
There is no restriction visiting both Avalanche and Emerald(but both Dams are closed for public visiting, may be with permission you can give a try). you have all the rights to drive on the shores of both these lakes.
Take Diversion from Emerald Bazaar(towards left on the way to Ooty).
You can also visit Pothimund Lake, Parson Valley and lake, Wenlock Downs(back side of Sandynulla lake) via same route, this will actually take you to Thalakundha on Ooty-Gudalur road(NH 67).
I am not sure we can access Mukuruthi Lake deep inside Mukuruthi National Park.