Estuary Processes and Managment - River Dynamics and Integrated River Management - page 499

Fig. 8.35 Global distribution of extensive fish kills recorded as of 2006 (Woods Hole Oceanographic Institution,
http://www.whoi.edu)
Fig. 8.36 Conceptual diagram of nutrient sources and eutrophication symptoms
Case study— Taihu Lake, situated in the Yangtze River delta (30º55'42''-31º33'50''N and 119º53'45''-
120º36'15''E), is the third-largest freshwater lake in China, with an average depth of 1.9 m and a surface
area of 2,338 km 2 (Fig. 8.37). The lake is the source of drinking water supply for about 30 million people
in the surrounding cities, and helps irrigate millions of hectares of grain and cotton fields in a lush
agricultural region. In addition, it sustains one of China's most important fisheries for crab, carp, and eel.
Even though the lake system is fed by over 200 streams in a river basin of 36,900 km 2 , the discharges of
most of these streams are very limited. For example, the mean discharge of the largest tributary is relatively
small, only 26.8 m 3 /s. Both field and modeling studies reveal that the circulation of this lake is primarily
driven by wind, and its hydraulic retention time is around 300 days.