Abstract: Along with the rapid economic growth, water environment has drastically deteriorated in the Taihu Lake Basin (TLB) during the past decades. However, the spatiotemporal patterns of water pollution are not yet fully understood at landscape scales in the TLB. Especially, the relationship between the lakes and rivers has been rarely examined. Using redundancy analysis, we studied the correlation of water quality between the lake body of Taihu and its inflow and outflow rivers based on the observation records from 82 monitoring sites in the TLB during 2006-2012. The correlation was examined at five spatial scales, i.e., 5, 10, 20, 40 and 80 km. Water quality was generally poor in the whole basin during the study period. However, the proportion of the major water quality indices that exceeded the national standard III varied at different scales. In general, water quality of the lake body was better than that of the inflow rivers, while the outflow rivers showed worse water quality than the inflow rivers. The inflow rivers were the main source of nutrient input for the Taihu Lake. In terms of water quality indices that exceeded the standard, the inflow rivers explained over 50% of the variance in the lake body (75.9%, 67.4% and 57.4% for DO, TP and AN, respectively). At single spatial scales, water quality of the lake body generally responded to the changes of water quality of the inflow rivers within a distance of 5 km from the lake body while had no significant response at other scales. In contrast, water quality of the outflow rivers was less affected by that of the lake body. The lake body only explained less than 7% of the variance in the outflow rivers, in terms of water quality indices that exceeded the standard. Moreover, no obvious scale effect was observed. Water quality of the outflow area was more affected by the pollutants from the surrounding lands rather than those transferred from the inflow rivers.

Key words: alfalfa, assimilation product, tolerance, Odontothrips loti