Longitudinal heterogeneity of phosphorus and phytoplankton concentrations in deep-valley reservoirs

Seasonal patterns of hydrodynamics, phosphorus loading and phytoplankton bi omass were studied in four deep-valley reservoirs. In highly elongated deep reservoirs dominated by one major tributary input, the heterogeneity incre ased with increasing retention time; other parameters such as depth, trophi c status, and wind exposure had little or no effect. The average whole-rese rvoir chlorophyll-a concentrations (Chla) agreed well with the Vollenweider /OECD model, however, Chla in lacustrine parts of reservoirs with steep lon gitudinal gradients lay partly out of 95% confidence interval of the model. Causes of deviation from the model are discussed.