A thorough flow and consisting of upper-, mid-, and lower-reaches, the Ranwu Lake in the southeastern part of the Tibetan Plateau is located in the upper reach of the Parlung Zangbo, with glacial melting as one of its major water supplies. Lake level, temperature and runoff were studied every week during May-October, 2009, to understand the hydrological variation of glacial-fed lakes with global warming.

Lake level and temperature were measured using Hobo automatic gauge every half an hour, showing larger variation in lake level of the lower reach than that of the mid-reach and attributive to converging feature of the lower reach and its comparative narrowness. Meanwhile, temperature of the lower reach turned out to be a bit higher than that of the mid-reach (averaging at 9.28℃), pointing to the gradual warming of glacial-melt during its transportation downstream.

Runoff of the lake was investigated weekly with RiverSurveyor, yielding such data as daily variation in velocity, water runoff, and water-carrying section. Raw data showed the largest lake runoff as 225.5 m³/s on August 4 while the smallest runoff as 25.8 m³/s as on October 28, with the total outflow of the lake during observation 1.87 billion m³.

Continuous observation of lake level at various sections of the Ranwu Lake started from 2007, providing first-hand data to studying the relationship between lake variation and glacial shrinkage in the upper reaches. The monitoring of Lake hydrology this year obtained data of lake level and runoff throughout the melting season, conducive to a systematic understanding of responses of Ranwu Lake hydrological and surrounding glacial mass balance variation to global climate changes, and shedding light on the influence of regional hydrological variation on local climate and eco-environment.