Gokyo lakes are located in Khumjung Village Development Committee of Solukhumbu District in Sagarmatha Zone in north-eastern Nepal. Gokyo Cho, also called Dudh Pokhari, is the main lake with an area of 42.9 ha (106 acres), and the village of Gokyo lies on its eastern shore. Thonak Cho is the largest lake with an area of 65.07 ha (160.8 acres). Gyazumpa Cho is 29 ha (72 acres) in size, followed by Tanjung Cho with an area of 16.95 ha (41.9 acres), and Ngojumba Cho with an area of 14.39 ha (35.6 acres). As sources of permanent fresh water they have high hydrological value. They feed on waters from various sources, such as seepage from the Ngozumpa glacier, a stream coming from the Renjo La pass from north-west and another stream originating from the Ngozumpa glacier in the east. These are glacier-fed freshwater wetlands and discharge water to the Dudh Kosi headway via the Taujon Lake and the Longabanga Lake. These lakes are deeper than previously assumed by the researchers. Fourth Lake (Thonak Cho) is the deepest lake (62.4m) followed by the Gokyo Lake which is 43 m. A direct connection between the Gokyo Lake and the upper Thonak Cho and the Ngozumpa Cho has not been observed, but these lakes may be connected via underground seepage water. The Gokyo lake system is naturally vulnerable, as it is lying in an ecologically fragile and unstable zone. The outburst of Ngozumpa glacier is always a threat to the existence of the lakes.