Satellite observations make it possible to estimate Poyang Lake's water budget

Using moderate resolution imaging spectroradiometer (MODIS) satellite imagery with hydrologic and meteorological data, we developed a box model to estimate the water exchange between Poyang Lake (the largest freshwater lake of China) and the Changjiang (Yangtze) River from 2000 to 2009. Significant intra- and inter-annual variability of the water budget was found, with an annual mean outflow of Poyang Lake of 120 : 2 +/- 31 : 2 billion m(3) during 2000-2009 and a declining trend of 5.7 billion m(3) yr(-1) (p = 0.09). The impoundment of the Three Gorges Dam (TGD) on the Changjiang River in June 2003 led to a rapid lake-river outflow of 760.6 million m(3) day(-1), resulting in a loss of 7864.5 million m3 of water from the lake in a short period. Shortly thereafter, a statistically significant decrease in the drainage basin's runoff coefficient was discovered. These findings provide large-scale evidence on how local precipitation and the TGD control the lake's water budget, where continuous monitoring using the established approach and satellite data may provide critical information to help make water management decisions.