Delineation of lakes and reservoirs in large river basins: An example of the Yangtze River Basin, China

One of the major impediments to water resources management in developing countries has been the fragmented nature of available data on the surface area, size and distribution of natural lakes and artificial reservoirs. In this study we used a parsimonious method based on remote sensing techniques to identify and extract water bodies in the Yangtze River Basin and classify them into three main categories: natural lakes, artificial reservoirs and rivers. This method combines data from the best available free sources, resulting in higher data quality. Using Landsat TM/ETM + images, we delineated nearly 43,600 reservoirs and 42,700 lakes and estimated a total quantity of 0.7 million smaller (surface area < 0.0036 km2) reservoirs and 0.5 million smaller lakes. The combined surface area of the reservoirs was ca. 8600 km2 with a total storage capacity of ca. 288 km3, and the total surface area of natural lakes was ca. 16,200 km2, with a total storage capacity of only 46 km3. These results indicate that the 43,600 reservoirs are capable of storing a volume of water equaling nearly 30% of the annual mean runoff in the Yangtze basin, but there is considerable geographic variation in the potential surface water impacts. Capacity–area ratios, which are strong indicators of the general hydrologic effects of reservoirs, range from 22,600 m3 km− 2 in the Jinshajiang tributary to 347,500 m3 km− 2 in the Poyang Lake Region. The greatest river flow impacts may occur in the Hanjiang tributary, where the reservoir capacity is equivalent to up to 90% of the mean annual runoff. The results of this study show that the Yangtze River Basin, which was previously dominated by natural lakes, has become dominated by reservoirs as a result of reservoir construction and the shrinkage of natural lakes.