Abstract: Based on the investigation data of the hydrology and water quality of three input rivers (Nanzhang, Shizi and Jianghe) of Zhangze Reservoir in 2006-2007, this paper studied the main hydrological characteristics and the nitrogen and phosphorus concentrations and their monthly flux dynamics in the rivers. The
flow speeds of the three rivers were slow, and the water temperature was suitable, with an annual mean value 12.5 ℃-15.1 ℃. The water temperature increased
rapidly from March to May, and became higher in summer. Accompanying with adequate sunlight, the higher water temperature in summer induced the occurrence of algal bloom. The yearly average concentrations of total nitrogen and phosphorus in the three rivers were 1.75-8.90 mg·L^-1 and 0.005-3.760 mg·L^-1, respectively, being relatively higher in general. Shizi River contributed 48.3% of the total nitrogen and 77.3% of the total phosphorus to the Zhangze Reservoir. Dissolved inorganic nitrogen was the major form of total nitrogen, which was dominated by nitrate nitrogen (NO₃^--N), accounting for 60% or more. The
nitrogen and phosphorus fluxes had no obvious seasonal variation, and their monthly fluctuations were also gentle. Point pollution was the main source of the ni
trogen and phosphorus in Nanzhang and Shizi rivers, while the nitrogen in Jianghe River was mainly come from nonpoint pollution. To protect the Zhangze Reservoir, it would be critical to control the point source pollution of Nanzhang and Shizi rivers.

Key words: Taibai mountain, Kindonia uniflora population, Age structure, Life table