A simple model of nitrogen retention in reservoirs

The total nitrogen mass balance was studied over a two-year period in two reservoirs located in south-eastern Poland. The observed nitrogen retention (N-ret) in the reservoirs ranged from 0.18 to 2.12 g m(-2)d(-1) (mean 0.83 g m(-2) d(-1)) in case of the Rzeszow Reservoir and from -0.02 to 0.41 g m(-2) d(-1) (mean 0.13 g m(-2) d(-1)) in case of the Solina Reservoir, while the percentage retention (N-ret%) ranged from 7 to 42% (mean 22%) and - 15 to 73% (mean 35% respectively. A good relationship between Nret and nitrogen loads was observed for the Solina Reservoir. The data obtained by the author and collected from the researches of 6 other reservoirs located in southern Poland were used to develop an empirical model suitable to predict the nitrogen seasonal dynamics in a reservoir. The model allows for the determination of both the annual mean N-ret value and its seasonal variation in a reservoir.