호수내 인의 주요원으로 몬순 유입수 = Monsoon Inflow as a Major Source of In - lake Phosphorus

다국어 초록 (Multilingual Abstract)

Spatial and temporal variation of phosphorus in response to intensity of summer monsoon was evaluated in Taechung Reservoir during 1993∼1994. Total phosphorus (TP) averaged 31 ㎍/ℓ during the study and varied from 6 to 197 ㎍/ℓ. Concentrations of TP were highest in the headwaters during the monsoon of July∼August 1993, and these values were mainly made of particulate P and were closely associated (R²=0.74, p < 0.001) with high inorganic suspended solids (NVSS). In-lake TP in the headwaters was mainly influenced by the watershed runoff and declined toward the dam. Values of TP downlake was only one-fifth of the peak in the headwaters and had no correlation with NVSS. In 1994, inlake TP was markedly lower relative to 1993 and showed low spatial and temporal variation. Maximum TP during monsoon 1994 in the headwaters and mid-lake was 72% and 52% lower, respectively, than in those two zones in 1993 whereas TP downlake was similar between the two years. These results suggest that temporal variation downlake is much less influenced by seasonal inflow compared to the headwaters. In 1993, mean TP before fall overturn, based on average value for all sites, was significantly (t = 5.99, p < 0.001) greater than the mean after fall overturn, whereas in 1994 mean TP after fall overturn (32 ㎍/ℓ) was greater. This outcome indicates that in 1993 major P-input originated from the external source from the watershed during the intense monsoon, whereas in 1994 internal processes dominated during the weak monsoon. Overall data suggest that annual budget of inlake P is regulated by intensity of the summer monsoon, and phosphorus data measured at single site near the dam or headwater zone may not be represent seasonal trends of the system due to large spatial variation of Taechung Reservoir.