Potential influence of different loading scenarios of Lake Peipsi (Estonia/Russia) on water quality, trophic status and the situation of fish stocks

phytoplankton, fish stock, ecosystem modeling Lake Peipsi and its watershed Lake Peipsi (3,555 km2, mean depth 7.1 m) is one of the most important lakes in Europe and has the fourth largest surface area after Lakes Ladoga, Onega, and Vänern. Located on the Estonian-Russian border (Fig. 1), L. Peipsi is a transboundary waterbody and the largest international lake in Europe. L. Peipsi consists of three parts: northern L. Peipsi s.s. (2,611 km2, mean depth 8.4 m) and southern L. Pihkva (708 km2, mean depth 3.8 m) are connected by the narrow river-shaped L. Lämmijärv (236 km2, mean depth 2.6 m). Residence time of the water is about 2 years, the outflowing River Narva runs its waters into the Gulf of Finland (Jaani, 2001). All three parts of L. Peipsi are divided between Estonia and Russia (Table 1). For calculation purposes, the drainage basin can be divided between L. Peipsi s.s., L. Pihkva and L. Lämmijärv as given in Table 1. However, in reality the three parts of the lake are arranged hierarchically so that the drainage basins of lakes Pihkva an