Total reservoir phosphorus loading and epilimnion phosphorus loading were estimated and their relations to phytoplankton quantity examined for spring-summer periods during 1984-1991 in Ěímov Reservoir, a stratified, moderately eutrophic reservoir with variable surface and deep outlets operation. Epilimnion phosphorus loading was quantified from the volumes of water entering the epilimnion due to the inflow temperature-density currents and due to the surface discharges that were determined by the one-dimensional dynamical simulation model of reservoir hydrodynamics DYRESM 5. The fraction of total phosphorus input into the reservoir entering the epilimnion varied between 12 and 31% in different years. Chlorophyll a concentration measured near the dam correlated only with the epilimnion phosphorus loading due to surface discharges. The phosphorus input by river water entering directly the epilimnion caused an increase of the chlorophyll a concentration at the dam only occasionally if the wind was of sufficient velocity and favourable direction to induce mixing and transport of epilimnion water masses from the headwater part of the reservoir to the dam.

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